J.H. McANDREWS

Departments of Botany and Geology, University of Toronto, 25 Willcocks St., Toronto ON M5S 3B2 Canada

Two contrasting sites with fossil digesta (gut contents and dung) illustrate herbivore diets. January Cave, Alberta (50^o 11' N, ll4° 31' W, 2040 m asl), is a rock shelter surrounded by Rocky Mountain subalpine forest of Pinus contorta; it lies 400 m below alpine tundra. The landscape was not glaciated. Unlike the modern pollen rain, the dry cave earth of weathered limestone had <7% tree pollen and most pollen was of entomophilous alpine tundra plants such as Claytonia, Phlox, Polemonium, Polygonum viviparum and Saussurea. Contemporaneous bones, dominated by the rodents Peromyscus and Spermophilus but also including small carnivores, date 33,000 to 23,000 yr B. P. Most pollen was transported to the cave in rodent digesta by birds of prey (mostly owls) and small carnivores.

The Hiscock Site, New York (43° 05’ N, 78° 05’ W, 189 m asl), in the St. Lawrence Lowland is a 0.8 ha Typha-dominated terrigenous peatland surrounded by farm fields. Following deglaciation 12,500 yrs B. P., a salt-water pond attracted vertebrates and a mastodon bone-rich Fibrous Gravelly Clay layer dating 11,450 to 10,200 yr B. P. was deposited. It contains a Picea glauca-dominated tree pollen assemblage that indicates spruce woodland. There is also super-abundant pollen of non-arboreal upland plants – Gramineae, Cyperaceae, Compositae and Rosaceae (probably Potentilla fruticosa), together with occasional pollen of entomophilous Lonicera, Cornus, Ericaceae, Elaeagnus, Salix, Shepherdia canadensis, Ranunculus, Epilobium, Galium, Campanula, Sanguisorba and Polygonum bistorta and anemophilous Thalictrum, Chenopodiineae, Artemisia, Plantago major type, Selaginella selaginoides, Botrychium, Lycopodium annotinum and fungal spores. This palynomorph assemblage, together with barkless spruce twigs, spruce needle fragments and clay testifies that the layer is digesta from mastodon, who browsed on spruce trees and shrubs, grazed on herbs and ate soil.

MICROPALEONTOLOGICAL INSIGHTS INTO PACIFIC PALEOPRODUCTIVITY: IMPLICATIONS FOR LATE CENOZOIC GLOBAL CLIMATE CHANGE

F.M.G. McCARTHY

Department of Earth Sciences, Brock University, St. Catharines, ON CANADA L2S 3A1

Schlumberger, Kokstadveien 34, 5257 Kokstad NORWAY

Department of Earth Sciences, Brock University, St. Catharines, ON CANADA L2S 3A1

Calcareous sediments do not normally accumulate in the extra-equatorial abyssal Pacific despite the abundance of calcareous plankton in surface waters, because the carbonate compensation depth (CCD) is shallower than the seafloor. Calcareous sediments (>5% CaCO₃) have been identified well below the CCD in the mid latitude North Pacific: five intervals of anomalous carbonate preservation were dated ~6.3, 5.1, 3.6, 2.5 and 0.7 Ma at ODP Site 881 (~5530 m water depth, 47^o6'N, 161^o29'E), and four calcareous intervals were dated ~3.6, 2.5, 1.65 and 0.9 Ma at Site 1179 (~5565 m water depth, 41^o4'N, 159^o58'E'). This extends the cycles of carbonate preservation in the abyssal Pacific Ocean beyond the equatorial latitudes where they have long been recognised. Because the abyssal Pacific Ocean between 50^oN & 50^oS comprises ~1/3 of the Earth’s surface area, the amount of CO₂ sequestered in these sediments may have driven the global cooling documented for these times in geologic history.

Although carbonate preservation cycles appear to be linked with global climate change, their cause is not yet fully understood and remains one of the more intriguing paleoceanographic problems. Palynological data show that the intervals of carbonate preservation in the mid-latitude western Pacific were associated with enhanced terrigenous flux (high concentrations of pollen and embryophyte spores) and sea surface productivity (high concentrations of the cysts of dinoflagellates). Primary productivity may have been enhanced during times of increasing continental aridity in Asia, when dust (including limiting nutrients like iron) was transported offshore by westerly winds. We suggest that the greater flux of particles to the seafloor, including the remains of calcareous plankton, depressed the CCD and increased burial rates, allowing carbonates to accumulate (including well-preserved planktonic foraminiferal tests in some samples). Cysts of heterotrophic dinoflagellates are abundant in samples with planktonic foraminifera but not in those intervals with recrystallised calcite. This is consistent with the theory of greater flux resulting in rapid burial and enhanced preservation, because the protoperidinioid cysts of heterotrophic dinoflagellates are much more susceptible to degradation than the gonyaulacoid cysts of autotrophic dinoflagellates. Siliceous microfossil assemblages (diatoms, silicoflagellates and radiolarians) show no correlation with the anomalous CaCO₃ peaks, suggesting the anomalous preservation did not result from changes in surface water masses or currents (e.g. Kuroshio Current).

PALYNOLOGICAL RECORD OF MIOCENE SEQUENCES IN THE U.S. MIDDLE ATLANTIC COASTAL PLAIN: INITIAL RESULTS FROM THE BETHANY BEACH BOREHOLE, DELAWARE

P.P. McLaughlin, Jr

Delaware Geological Survey, University of Delaware, Newark, DE 19711, USA

K.G. MILLER

Dept of Geological Sciences, Rutgers University, Piscataway, NJ 08854, USA

Delaware Geological Survey, University of Delaware, Newark, DE 19711, USA

Dept of Geological Sciences, Rutgers University, Piscataway, NJ 08854, USA

The Bethany Beach borehole provides a nearly continuous record of the Miocene of the Delaware Coastal Plain.  This 1470-ft-deep, continuously cored hole penetrated Miocene sequences near their maximum regional thickness, yielding new insights on the influence of sea level, tectonics, and sediment supply on the depositional history of the area.

The Miocene section is predominantly a stack of highstand systems tracts composed of shallow- and marginal-marine clastic sediments.  Sequence boundaries are recognized where significant flooding events coincide with unconformities and have been dated using Sr-isotope biostratigraphy.  The Miocene succession passes upward from glauconitic sands and silts in the lower part of the lower Miocene, to four thick (100-270 ft) shallow-marine sequences of silt and sand in the upper part of the lower Miocene, to three thinner (50-100 ft) sand- and shell-rich nearshore sequences that comprise most of the middle Miocene.  These are overlain by two finer-grained, glauconitic shelf sequences in the upper part of the middle Miocene.  The overlying upper Miocene (to possibly Pliocene) section is a coarsening- and shoaling-upward succession of shallow marine clastics, capped by interbedded sands and muds deposited in beach and estuarine environments.

Palynological analysis reveals a Miocene flora dominated by Quercus, with common Carya and Pinus, and several "exotic" taxa that do not presently live in the area.  The lower Miocene assemblages are mostly composed of temperate and warm-temperate arboreal forms, but have common subtropical to tropical exotics, including common Engelhardia-type pollen and scattered Podocarpus.  Middle Miocene assemblages are similar but have fewer exotics; Engelhardia-type pollen is most common but generally decreases upward, and Pterocarya, Podocarpus, and Symplocos are present.  A shift to fewer Pinus and more non-arboreal pollen (Compositae, Gramineae, and Umbelliferae) occurs in the upper part of the middle Miocene.  The character of the assemblage continues to change in the upper Miocene (to possibly Pliocene) section, with more abundant Carya, a decline of non-arboreal types, and a gradual increase in style='color: black'>Liquidambar.   Exotics are consistent but less abundant, with rare Pterocarya and scattered occurrences of Engelhardia-type pollen, Podocarpus, and cf. Dacrydium.

Overall, the palynological data reflect subtropically influenced warm-temperate aboreal environments in the Miocene of this area, but with a decrease in subtropical influences through the middle and late Miocene.  Dinoflagellates are present, reflecting marine deposition at this site, but are less abundant and diverse upward.  The increase of non-arboreal pollen in the later middle Miocene may record a drier period, and the late Miocene increase in Carya and Liquidambar may reflect subsequent wetter conditions.

CURRENTLY ACHIEVED RESOLUTION IN BIOCHRONOSTRATIGRAPHY AND SEQUENCE STRATIGRAPHY BASED ON DINOFLAGELLATE CYSTS AND SPORE-POLLEN IN THE PETROLIFEROUS BASINS OF INDIA

N.C. MEHROTRA, H.S. ASWAL, KAMLA SINGH, D.S.N. RAJU

KDMIPE, ONGC Ltd., 9 Kaulagarh Road, Dehra Dun –248 195 (India)

The paper presents a review of dinoflagellate and spore–pollen studies in various commercial hydrocarbon producing basins of India and the resolution achieved so far in biochronostratigraphy and their application in sequence stratigraphy. In Cambay Basin five dinoflagellate biohorizons have been identified within Ypresian and the resolution varies from 5.8 to 13.2 Ma. In Mumbai Offshore Basin twenty biohorizons have been distinguished between Ypresian to Miocene; fine time slicing upto one million year has been achieved.

In Cauvery Basin dinoflagellate cysts have been useful in precisely dating Cretaceous to Early Eocene sediments and are partly tied up with planktic foraminifera. Maximum data is available from Krishna –Godavari Basin. Seventy-nine dinoflagellate biohorizons have been identified between Middle Triassic to Holocene with a fine time slicing from 0.5 to 1 Ma. Standard biozonation of Triassic to Holocene sediments has been achieved. Seventy-eight interval zones have been distinguished and tied up with foraminiferal data. In Assam Basin, seven biochronohorizons have been distinguished between Thanetian top to Priabonian and resolution varies from 3.3 to 17.8 Ma.

Dinoflagellate cyst biohorizons have helped to build a high-resolution biostratigraphy and further strengthened by available foraminiferal data. Application of terrestrial palynofossils and dinoflagellates has been made to develop paleoenvironmental models in each of the studied basins. Paleogeographic reconstructions in Panna Formation, Mumbai Offshore has been done at one million year interval within Ypresian (54 to 49 Ma) based on integrated data.

Application of dinoflagellate cysts in building sequence biostratigraphy has been made in Krishna–Godavari Basin; a case history from Ramachandrapuram area has been cited where ten depositional sequences have been identified between Oxfordian to Late Maastrichtian. The data is integrated with other parameters like seismic and well logs to be applied in exploratory analysis.

The importance of dinoflagellate cysts in the Mesozoic–Cenozoic biochronostratigraphy of India is enhanced partly because of the absence or presence of only rare non–diagnostic age markers like foraminifera in very shallow marine facies. On the other hand resolution based on spore–pollen is crude but valuable in classification where dinoflagellate cysts and other markers are absent as in case of Tripura–Cachar and Schuppen Belt of North Eastern India. In case of Upper Assam Shelf zones of spore –pollen and dinoflagellate cysts are tied up.

Potential of dinoflagellate cyst studies in deep water exploration research has been outlined.

 PALYNOLOGY OF THE LOWER CRETACEOUS McMURRAY FORMATION, ALBERTA, CANADA

D. MICHOUX

TotalFinaElf, CSTFJ, Avenue Larribau, 64000 Pau, France

The Lower Cretaceous McMurray Fm is the main reservoir of the Athabasca heavy oil province of Alberta, western Canada. These deposits are currently being developed by two unconventional techniques: surface mining and in situ thermal Steam Assisted Gravity Drainage (SAGD). The definition of an accurate geological model is important for the drilling strategy associated with SAGD. This is made especially difficult by complex lithofacies variations. The marginal character of the Mc Murray in terms of depositional environment results in a specific biological context, with virtual absence of nannoplankton/foraminifera, but rich and diverse palynological assemblages. The aim of this palynological analysis was thus to contribute to the interpretation of the depositional environment of these deposits, using field samples collected along riverbeds in the Fort McMurray area.

Palynological assemblages are dominated by land-derived pollen and spores. A planktonic fraction is however always present, varying qualitatively and quantitatively. It is subdivided into 3 categories:

-Freshwater microplankton (including freshwater dinocysts). Well-documented freshwater types are present. They include single-celled forms (Lecaniella, Ovoidites, Schizosporis) as well as algal colonies (Pediastrum, Scenendismus). Several freshwater dinoflagellate species were described from the Wealden were also recorded: Hurlandsia rugaris, Kallosphaeridum inornatum.

- Marine dinoflagellates. Most forms recorded within the McMurray Fm belong to well-known Cretaceous genera and species, some described in the district of Mackenzie, Canada.

-low salinity microplankton. Most forms included in this category are undescribed at species level but belong to genera known to have freshwater representatives (Nyktericysta, Balmula), described in lacustrine basins from Canada and northern China. Typical low salinity assemblages are characterised by low diversity and low to moderate abundance. They also occur alongside marine dinocysts in higher salinity environments, probably reflecting salinity tolerance but also basinward transport.

Variations in type and frequency of the main palynomorph groups allowed the definition of 6 palynofacies. Their recognition and their succession complements the interpretation based on sedimentological features and trace fossils, and helps ascertain the geological model.

LATE CRETACEOUS DEPOSITIONAL ENVIRONMENTS, NORWEGIAN SEA: APPLICATIONS OF BIOSTRATIGRAPHY, REWORKING AND PROVENANCE STUDIES IN EXPLORATION MAPPING

P.S. MILNER, R. CORFIELD, E.K. HANSEN, K. NYBERG

BP Norge, Godesetdalen 8, P.O.Box 197, N-4065 Stavanger, Norway

HM Research Associates, 100 Main Street, Woodhouse Eaves, Leicestershire LE12 8RZ, U.K.

Examples from a series of sequence-based, regional Gross Depositional Environment maps are presented, addressing key issues on reservoir and source distribution in the Norwegian Sea. These illustrate the applications of biostratigraphic data in sequence/depositional environment and provenance studies, alongside new seismic and structural mapping.

Biostratigraphy has played a key role in refining and applying the Cretaceous sequence stratigraphic framework both in terms of correlation and the interpretation of depositional environments. These interpretations have been integrated into an updated understanding of the structural framework of the Norwegian sea, which includes a series of reconstructed palaeobathymetric maps through the Cretaceous and early Tertiary.  Integration of this work has enabled the regional mapping of 8 Cretaceous sequence intervals in terms of their Gross Depositional Environments.

The maps highlight the challenge of understanding the interplay and changing influences of uplift and erosion of the major sediment sources of East Greenland, Nordland Ridge and the Norwegian margin, particularly during the Late Cretaceous. Integration of Heavy Mineral/Provenance data with that of reworked fossil palynomorph occurrences has significantly impacted the overall depositional model. It has also highlighted some areas where further work is required to fully understand the nature of the depositional systems.

Three examples illustrating gross depositional environments within specific sequence intervals and areas are presented.

1) The Trøndelag Platform area during deposition of the main Lange Formation sandstones and a candidate source rock interval (Cenomanian-Middle Turonian, sequences K62-K68.

2) The Trøndelag Platform area during deposition of the main Lysing Formation sandstones (Late Turonian- Middle Coniacian, sequence K72).

3) The East Greenland/Vøring Møre Basin-Nordland Ridge area during deposition of the Nise Formation sandstones (Campanian, sequence K80).

CONTRIBUTION OF THE PALYNOLOGY OF COPROLITES TO THE KNOWLEDGE ON DISEASES AND THE PHARMACOPOEIA OF PREHISTORIC MEN OF PALEOINDIANS PEOPLE FROM PIAUSI, NORTH-EAST BRAZIL

S.A. de MIRANDA CHAVES

Fundação Oswaldo Cruz - Escola Nacional de Saúde Pública (ENSP) - Departamento de Endemias Samuel Pessoa, Rua Leopoldo Bulhões 1480, térreo - Manguinhos. Cep 21041-210 Rio de Janeiro - RJ, Brasil

The attention given to the study of well-preserved coprolites collected on archaeological sites dates to the end of the XIX and the beginning of the XXth century. Since that time prehistorians and palynologists have been preoccupied with the beginning of agriculture and the anthropical effects upon the environment. Our study is directed towards the coprolites collected in sediments from the rock-shelter of Pedra Furada located in the Piaui State, North-East, Brazil (8° 50’ 10" S - 42° 33’ 20" W). This rock - shelter presents a 5m thick filling whose sequence contains 3 Pleistocene and 3 Holocene layers with human influence. The pollen from these coprolites were analyzed. The results have given a very important palaeoethnological data. Evidence emerges regarding the range of medicinal and food plants of the prehistoric humans who inhabited the site for some 1500 years (8 500 - 7000 B.P.).

SEQUENCE BIOSTRATIGRAPHY IN THE HAIMA SUPERGROUP, CENTRAL OMAN

S.G. MOLYNEUX

British Geological Survey, Keyworth, Nottingham, NG12 5GG, UK

Petroleum Development Oman, PO Box 81, Muscat 113, Sultanate of Oman

Reservoir Laboratories AS, P.O. Box 96, Postal Code 116, Mina Al-Fahal, Sultanate of Oman

Petroleum Development Oman, PO Box 81, Muscat 113, Sultanate of Oman

Discoveries of significant gas/condensate reserves in the Haima Supergroup of Central Oman highlight the need to understand the stratigraphic architecture of the supergroup, to identify stratigraphic traps and determine the relationships between reservoirs and seals.  Biostratigraphy has a role to play in determining Haima stratigraphy, but until now biostratigraphic schemes have been imprecise, individual zones often spanning one or more lithostratigraphic units and chronostratigraphic divisions.

New palynological studies hold the promise of higher biostratigraphic resolution.  At their heart lies the recognition that marine flooding events in the Haima Supergroup are characterised by unique assemblages of marine palynomorphs.  In the upper Haima (Mahatta Humaid and Safiq groups), distinct and often diverse marine palynomorph assemblages occur in the Late Cambrian, Early Ordovician (Late Tremadoc), Middle Ordovician (Llanvirn), Late Ordovician (separate Caradoc and Ashgill assemblages) and Early Silurian (Llandovery).  The intervening strata yield low diversity and generally sparse palynomorph assemblages that indicate marginal marine and non-marine environments.

Recognition of distinct marine assemblages has led to more precise correlation between subsurface sections in the Haima Supergroup, and to a better understanding of stratigraphic relationships, including lateral facies trends.  Furthermore, the discrete assemblages provide data to test sequence stratigraphic models developed for the Arabian Plate, as they should exhibit a spatial relationship to candidate maximum flooding surfaces.  Viewed in the context of sequence stratigraphy, the biostratigraphy being developed for Central Oman may have wider application for the Arabian Plate as a whole.

MORPHOSTRATIGRAPHY – A NEW NON-TAXONOMIC BIOSTRATIGRAPHIC TECHNIQUE APPLIED TO A BIOTURBIDITIC DEEP SEA RESERVOIR, MAUREEN FORMATION, FLEMING FIELD, UKCS

E. MONTEIL

Geoscience Australia, GPO Box 378, Canberra, ACT 2601, Australia

Palynology is widely used in exploration for dating and correlating. However, since key markers may be rare or absent, it is sometimes difficult to identify sufficient bioevents to finely correlate wells, particularly at reservoir scale. This is especially crucial to compartmentalisation modelling and understanding production behaviour since many reservoirs occur within a single biozone. To solve this issue a new technique called morphostratigraphy has been successfully applied in the Maureen Formation reservoir.

The concept of morphological character stratigraphy (morphostratigraphy) was described by Monteil (1990), and defined as "the study of selected unambiguous morphological features varying in time". Classical biostratigraphy is based on the distribution of taxa through time, where taxa are defined by a unique set of morphological characters. Morphostratigraphy, however, is based simply on the distribution of morphological character through time. Morphological characters are treated either as individual units or as two or more characters in combination, regardless of their taxonomic affiliation.

Application of this new technique to the Maureen reservoir proves that morphostratigraphy provides greater biostratigraphic resolution than was achieved by the conventional approach, significantly improving reservoir correlations. This method highlighted a different partitioning of the reservoir, which explained production problems experienced by BG group. The study also clearly demonstrates the applicability of morphostratigraphy to refine correlations within deep marine turbidite settings.

CRETACEOUS-TERTIARY BOUNDARY IN THE DENVER BASIN, COLORADO – THE MOST COMPLETE K-T BOUNDARY SECTION KNOWN IN NONMARINE ROCKS

D.J. NICHOLS

U.S. Geological Survey, MS 939, Box 25046, Denver, CO 80225, USA

Denver Museum of Nature & Science, Denver, CO 80205, USA

Canadian Museum of Nature, Ottawa, Ontario K1P 6P4, Canada

U.S. Geological Survey, MS 939, Box 25046, Denver, CO 80225, USA

Denver Museum of Nature & Science, Denver, CO 80205, USA

A new Cretaceous-Tertiary (K-T) boundary locality in the Denver Basin, Colorado, is the most complete K-T boundary section known in nonmarine rocks. The new locality—the West Bijou Site—is established and verified by palynology and the presence of impact debris; it is within a magnetically reversed interval (subchron C29r) that is bracketed by vertebrate fossils (dinosaurs and mammals), Maastrichtian and Paleocene megafloras, invertebrate fossils, and radiometrically dated ash beds in a nonmarine fluvial setting. The boundary is marked by a tonstein-like parting within a lignite bed in the Denver Formation exposed along West Bijou Creek about 50 km ESE of Denver.

Palynological analysis of the West Bijou Site is based on 17 samples collected through an interval of 182 cm; the eight most important samples are from an interval of 35 cm centered on a 3-cm-thick, tonstein-like parting in the lignite. Assemblages from the parting and the lignite below it include a total of eight Maastrichtian pollen species: Ephedripites multipartitus, Libopollis jarzenii, Liliacidites complexus (the most abundant species), Myrtipites scabratus, "Proteacidites" spp., Retibrevitricolporites beccus, and Trisectoris costatus. Five of the Maastrichtian species are present in the uppermost Cretaceous sample, 0-1 cm below the parting; extinction of the Maastrichtian palynoflora is about 24% within 10 cm below the K-T boundary. None of the Maastrichtian species is present in the lignite just above the parting, or in lignite or carbonaceous claystone samples to the top of the measured section.  In the Paleocene samples, Arecipites tenuiexinous, Momipites inaequalis, Retitrescolpites anguloluminosus, and Thomsonipollis magnificus are notably abundant. A fern-spore "spike" has not been detected, but may be present within an unsampled 7-cm interval in the lignite above the lowermost Paleocene sample.

Shock-metamorphosed quartz grains are present within the parting and in the 1-cm-thick sample of lignite just above it.  Anomalous amounts of iridium have been detected in the parting; detailed measurements are underway.  The shocked quartz and iridium are debris from the Chicxulub impact crater, and are evidence that the plant extinctions were caused by the K-T impact event.

Associated vertebrate fossils include hadrosaurian dinosaur teeth about 4 m below the K-T boundary and the jaw of the Puercan (earliest Paleocene) mammal Protungulatum donnae about 12 m above.  Numerous megafloral assemblages reveal a Paleocene megaflora that is low in diversity (9-15 taxa), and this low diversity persists for about 250 Kyr into the Paleocene, based on calculations from the paleomagnetic data.

A NEW BIOSTRATIGRAPHY FOR THE LOWER PALEOCENE ONSHORE WEST GREENLAND AND ITS IMPLICATIONS FOR THE TIMING OF THE PRE-VOLCANIC EVOLUTION

H. NØHR-HANSEN, E. SHELDON

The Geological Survey of Denmark and Greenland (GEUS), Øster Voldgade 10, DK-1350 Copenhagen K, Denmark

G. DAM

DONG E&P, Agern Alle 24-26,DK-2970 Hørsholm, Denmark

In light of new biostratigraphic data from Nuussuaq, it is possible for the first time to provide an agreement between palynostratigraphic, nannostratigraphic, radiometric dating and magnetostratigraphic measurements from relatively closely situated sections in a restricted area in the North Atlantic Igneous Province; resulting in the dating of the initiation of volcanism onshore West Greenland.

On the basis of an integration of dinoflagellate cyst and nannofossil data, it has been possible to divide the Lower Paleocene succession on Nuussuaq into five dinoflagellate cyst zones (Trithyrodinium evittii, Cerodinium pannuceum, Senegalinium iterlaaense, Palaeocystodinium bulliforme, Alisocysta margarita) and correlate with global nannoplankton zonation.

The uppermost pre-volcanic marine mudstone succession has been dated latest Danian (upper NP4) based on nannoplankton. The first occurrence of hyaloclastites and reworked volcaniclastic sandstones is broadly concurrent with the base of the Alisocysta margarita Zone indicating that volcanism in West Greenland began during latest Danian. The overlying and partly time equivalent volcanics were formed during chron C27n. These hyaloclastites underlie volcanics of chron C26r, which are dated as 60.9 and 61.3 Ma by ⁴⁰Ar/³⁹Ar measurements

Moreover, it is possible to date the events associated with rifting, tranquil uplift and valley and submarine canyon incision of the basin that occurred immediately prior to the volcanism in West Greenland.

Three pre-volcanic tectonic phases have been recognised, all associated with valley and submarine canyon incision. The first phase took place in the Late Maastrichtian and was followed by two phases in the Early Paleocene. The two Early Paleocene events took place during NP1–NP3, and were followed by rapid subsidence preceding volcanism in NP4.

LATERAL BIOFACIES CHANGES IN MID-CRETACEOUS HIGH-RESOLUTION SEQUENCES IN THE U.S. WESTERN INTERIOR

University of Missouri-Rolla, Department of Geology and Geophysics, 125 McNutt Hall, Rolla, MI 65409, USA

1227 Venice Street, Longmont, CO 80501, USA

Southeast Missouri State University, Department of Geosciences, Cape

Girardeau, MO 63701, USA

Tulsa University & Precision Stratigraphy Associates, RR3 Box 103-3,

Cleveland OK 74020, USA

1522 Ehlinger Road, Fayetteville, TX 78940, USA

Upper Albian-Lower Cenomanian sandstone, siltstone and shale units in the U.S. Western Interior represent several transgressive-regressive cycles associated with multiple marine connections between the Gulf Tethyan and northern Boreal regions. The units extend laterally for distances as great as 200 km and are separated by regional erosional contacts designated as sequence boundaries (SB). The two seaways were fully connected during the early part of the Late Albian when the Kiowa, Tucumari and Glencairn formations between SB2 and SB3 were deposited in the south, and the Thermopolis and Skull Creek formations were deposited in the north. The connection closed during the later part of the Late Albian regression, but it was re-established during the Early Cenomanian with the deposition of the Graneros Shale in the south and the Belle Fouche Shale in the north.

More than 40 sections (below SB3 to above SB4) in SE Colorado, NE New Mexico, Oklahoma panhandle, Montana, and Wyoming have been studied to test the hypothesis that ephemeral connections existed between the cooler Boreal Sea and the warmer Tethyan Sea between SB3 to just above SB4. Such connections would have provided the opportunity for south to north biotic exchanges. The multidisciplinary techniques of sedimentology, sequence stratigraphy, palynology, micropaleontology, and organic geochemistry tentatively suggest that the two basins were briefly connected twice during the latest Albian and/or earliest Cenomanian. The occurrences of a low diversity agglutinated foraminiferal biota (e.g., Tethyan Ammobaculites and boreal Miliammina), nearshore dinoflagellate cysts, such as Cyclonephelium, Palaeoperidinium and Cribroperidinium, and the acritarch genus Pterospermella in these sediments suggests that the ephemeral connections were so brief that brackish conditions were established instead of fully marine conditions. This observation is supported by isotopic carbon signals and palynofacies analysis. In addition, ranges of dinoflagellate cysts are being calibrated with ammonites, in order to directly correlate the Albian/Cenomanian boundary from France to Montana.

MUNGO FIELD UKCS 22/20: BUGS, A DOSE OF SALTS, AND RESERVOIR DEVELOPMENT

S.N.J. PAYNE

BP Exploration Operating Company Ltd, Burnside Road, Farburn Industrial Estate, Dyce, Aberdeen, AB21 7PB, UK

Petrostrat Ltd, Tyldesley House, 48 Clarence Road, Craig-y-Don, Llandudno, LL30 1TW, UK

BP Exploration Operating Company Ltd, Burnside Road, Farburn Industrial Estate, Dyce, Aberdeen, AB21 7PB, UK

BP Norge, Godesetdalen 8, PO Box 197, 4065 Stavanger, Norway

Mungo is an oil and gas field located within the Eastern Trough of the UK Central North Sea, 250km east of Aberdeen. Discovered in 1989 with initial reserves estimated at 155 million barrels of oil and 79 bcf of gas, the field comprises a salt diapir flank structure reservoired largely within Paleocene turbidite sandstones, sealed beneath Eocene mudstones with an up-dip termination against Zechstein salt.

Biostratigraphic data from early wells suggested extreme geological complexity; reworking, caving and injection were all invoked. Guided by the principle that the dinocyst genus Apectodinium does not migrate into the North Sea until the S1a Unit of the Forties Member, interpretation focused on identifying the LDO of this genus. Once identified, this "golden spike" became the key to interpreting well stratigraphy. The complexity thereby imposed fitted notional models of a "Forties melange" reservoir, with older sediments chaotically slumped or reworked off the growing diapir. Inter-well correlation was rendered doubtful and the Mungo reservoir model was thereafter constructed stochastically.

Continued development drilling induced a further attempt to unravel the subsurface complexity. Emphasis was changed, downplaying the Apectodinium driven model, seeking instead any ghosting of an in-situ stratigraphy in the "melange". Re-analysis of biostratigraphic and core material, combined with heavy mineral analysis, has allowed a rationalisation. The prime reservoir is now assigned to the Maureen Formation, albeit with major Forties injection. The mechanism for this injection may involve the fissuring of older sediments due to diapir extension, allowing the entrainment of younger material. The revised stratigraphy allows eight Paleocene packages to be identified, important for reservoir layering, correlation and biosteering.

R.A. PENNEY

Reservoir Laboratories AS, PO Box 96, Mina Al-Fahal PC 116, Sultanate of Oman

XGL/3 Petroleum Development Oman, PO Box 81, Muscat PC 113, Sultanate of Oman

A refined biozonation of the Permo-Carboniferous Al Khlata Formation, Sultanate of Oman, is presented for which the number of subdivisions is increased from four to ten.  Owing to the extensive reworking of palynomorphs within these sediments, as a result of episodic glacial cover, the scheme is based mainly upon quantitative assessments of broad taxonomic groupings instead of inceptions and extinctions of individual taxa.  The variation in the proportion of these components upwards through the Al Khlata is a reflection of the palaeoevegetational change through time, which is thought to be the product of Oman’s changing latitudinal position and climatic amelioration associated with the waning of the Permo-Carboniferous Gondwanan glaciation.

This refinement of the palynostratigraphy improves the correlation potential for other Gondwanan sections both within and beyond the Arabian Plate.  Comparison with other palynomorph zonation schemes from within the Gondwanan realm suggest an age range for the Al Khlata from the Latest Moscovian (Westphalian D) to the Sakmarian, when related to faunal datings from Australian sections and their Russian correlatives.

Examples of four scales of practical application are given.  Firstly, on the exploration scale, where the core and sidewall core based zonation facilitates and constrains regional correlation of sequences, such that major depocentres and plays can be identified with associated reservoirs and seals.  Secondly, production field scale reviews of reservoir architecture, to facilitate future drilling strategies.   Thirdly, in updating existing field models by post-drill palynostratigraphic evaluation of cuttings samples in horizontal wells.  Fourthly, by near "real time" monitoring of horizontal well sections, where palynomorph recovery in cuttings samples permits.  In both the latter cases, the utilisation of palynological data from existing and pilot verticals, plus wireline log and/or wellsite lithological information, is essential for the interpretation of the palynological and kerogen signatures from the sub-horizontal sequences.

In all, this improved palynostratigraphic scheme has enhanced the exploitation of South Oman’s Al Khlata reservoirs substantially, saving millions of dollars in field development costs, in addition to providing data for near field and regional exploration.

VEGETATION, CLIMATE AND CYCLOSTRATIGRAPHY IN CENTRAL PARATETHYS DURING LATE MIOCENE AND EARLY PLIOCENE ACCORDING TO PALYNOLOGY

S.-M. POPESCU

PEPS, UCBL, 27-43 Boulevard du 11 Novembre, F69622 Villeurbanne Cedex (France)

High-resolution palynological analysis has been performed on five well-dated Early Pliocene sections from southeastern Europe: Hinova, Valea Visenilor, Husnicioara and Lupoaia in the Dacic Basin (southwestern Romania), DSDP Site 380A (Black Sea) which also includes latest Miocene sediments (Messinian).

Pollen floras show how this region was relatively protected from floristic extinctions which occurred in Europe during the Late Pliocene and the Quaternary because of glacial-interglacial cycles. A noticeable effect of Asian monsoon has probably encouraged persistence in this area of some themophilous species up today.

Altitudinal forest belts have been reconstructed on the southern Carpathians. Palaeo-Danube delta was rich in swamps inhabited by Cypress forest and marshes occupied by grasses (Cyperaceae) as today in Florida and Mississippi delta. The descent of the altitudinal gymnosperm belts is evidenced in relation with each "cooling" with respect to eccentricity 100 kyrs cycles. On contrary, warmer phases forced development of thermophilous trees and lignite deposition. Asian monsoon probably controlled opposing development of swamps and marshes with respect to precession 20 kyrs cycles. Precession minima (monsoon enhancement) advantaged marshes which requires more humidity than swamps. A comparison is possible with the Mediterranean sapropels, the forcing of which being also the precession rhythm. This suggests the establishment in Early Pliocene of a longitudinal gradient over the Mediterranean region. As today, a strong contrast separated vegetation features from Dacic and Pontic realms. In the latter, thermic cycles forced competition between thermophilous trees and Artemisia steppes, the early development of which announces their forthcoming development over the whole Mediterranean region in relation with earliest glacials (2.6 Ma).

Such high-resolution pollen analyses provide a very detailed climatic record for the region with respect to global climatic changes between 6 and 3.8 Ma. Resolution of pollen records reaches that of reference ?¹⁸O curves. So, weak variations in temperature and humidity occurring during the warm Pliocene will be more understood as well as their effects on the vegetation. The European Pliocene climatostratigraphy is confirmed and Central Paratethyan deposits receive for the first time a reliable cyclostratigraphy. Relationships will be easier with the reference Mediterranean marine sections.

Consequences of the Mediterranean Sea desiccation (Messinian salinity crisis: 5.7-5.32 Ma) over the Black Sea have been evidenced: they concern both coastal vegetation and dinoflagellate assemblages. A new idea of Mediterranean Sea – Central Paratethys relationships is proposed for a better explanation of the events bordering the salinity crisis.

LATE MAASTRICHTIAN DINOFLAGELLATE CYSTS FROM CERRO BUTALÓ SECTION, SOUTHERN MENDOZA PROVINCE, ARGENTINA

M.B. PRÁMPARO, O.H. PAPÚ

Unidad de Paleopalinología. Instituto Argentino de Nivologia, Glaciologia y Ciencias ambientales (IANIGLA)- CRICYT. C.C.131. (5500) Mendoza, Argentina

The late Cretaceous Atlantic trangression is recorded in western Argentina in the sediments of the upper part of the Malargüe Group. The Cerro Butalo section crops out at 35º 50' S and 69º 40' W, southern Mendoza Province, Argentina and is constituted by sediments of the Jagüel Formation and Roca Formation, both belonging to the Malargüe Group. The Jagüel Formation at the study area is 25m thick and is characterized by grey mudstones and sandstones. The Roca Formation overlies the preceding unit and comprises a basal white limestone (30m thick) with abundant bivalves and gastropod fragments, followed by pelitic sandstones (20 m thick). These two units correspond to the third depositional sequence  (DSIII) in the sense of Parras et al. (1998), deposited in a subtidal to intertidal environment, and are overlain by the terrestrial Pircala Formation. 

A well preserved palynological association was recovered from this section. Dinoflagellate cysts are dominating in the lower part of the profile (Jagüel Formation). Representatives of the Spiniferites/Achomosphaera group dominate the association. Biotratigraphically useful species are Areoligera medusettiformis, Areoligera coronata, Deflandrea galeata, Glaphyrocysta retiintexta, Hystrichosphaeridium tubiferum, Phelodinium magnifica, Palaeocystodinium lidiae, Paleocystodinium golzowense, Piercites pentagona. Several species of the genera Cordosphaeridium, Florentinia and Tityrosphaeridium are also common in this interval. Terrestrial palynomorphs are scarce in all the samples but become more abundant at the top of the section (Roca Formation). Spores and massulae of aquatic ferns (Azolla cretacea, Azolla (Rhizosperma) sp., Azollopsis (Spiralopsis) pusilla, Grapnelispora loncochensis) reflect the vegetation of the littoral environment and are stratigraphically useful. Gymnosperm pollen like Classopollis, Callialasporites, Cyclusphaera, Podocarpidites are present, associated with angiosperm pollen assigned to Psilatricolporites patagonicus, Peninsulapollis gillii and the zygnematacean algae Catinipollis.

Deflandrea galeata has a first occurrence in the middle Late Maastrichtian of the Danish part of the North Sea. Disphaerogena carposphaeropsis has its first appearance (FAD) in the Late Maastrichtian (67.0 M.A.). Based on the occurrence of these two species, the Jagüel Formation at the Cerro Butalo section is considered to be of Late Maastrichtian age. Within the uppermost 10m of Roca Formation dinoflagellate cysts become scarce; only specimens belonging to Operculodinium centrocarpum are present, indicating a nearshore depositional environment. The KPB at this section is considered to be (paleontological evidence and radiometric dating) located in the continental deposits of Pircala Formation (DSIV). This is the first report of a Late Cretaceous dinoflagellate cysts association of the Mendoza Province, western Argentina.

SHORT-TERM ENVIRONMENTAL CHANGE DURING MID-CRETACEOUS BLACK SHALE FORMATION: MICROPALEONTOLOGICAL EVIDENCE FROM THE UPPER APTIAN AND LOWER ALBIAN OF THE VOCONTIAN BASIN (SE FRANCE)

J. PROSS, J.O. HERRLE, O. FRIEDRICH, C. HEMLEBEN

Institute of Geosciences, Sigwartstr. 10, D-72076 Tübingen, Germany

In order to better understand paleoclimatic and paleoceanographic changes during the mid-Cretaceous, we have studied palynomorphs, calcareous nannoplankton, and benthic foraminifera from black shales in the Vocontian Basin (SE France). To assess the mechanisms leading to black shale formation on different scales, the supraregionally distributed Niveau Paquier Paquier (Oceanic Anoxic Event 1b, Early Albian) and the regionally distributed Niveau Kilian (Late Aptian) were investigated. As both the Niveau Paquier and the Niveau Kilian formed under relatively high sea level in basically identical paleo-latitudes, a framework is provided to compare the formation of obviously different black shales under partly identical boundary conditions. We used palynomorphs as a proxy for terrestrial input and humidity, calcareous nannofossils as a proxy for surface water temperature and productivity, and benthic foraminifera as a proxy for bottom water oxygenation and organic matter flux.

For the supraregionally distributed Niveau Paquier, our data show short-term increases in terrigenous input, humidity, temperature, and productivity associated with decreases bottom water oxygenation. The signals occur within the precessional band and are modulated by eccentricity. As can be inferred from the high spore/pollen ratio in the Niveau Paquier samples, the formation of the Niveau Paquier generally occurred under extremely humid conditions.

The regionally distributed Niveau Kilian shows environmental changes similar to those occurring during formation of the Niveau Paquier. Differences exist, however, in the duration of black shale formation and the amplitude of changes. They are related to the extent of humidity and temperature increases during black shale formation. The spore/pollen ratio in samples from the Niveau Kilian is much lower than in those from the Niveau Paquier, indicating generally less humid conditions during its formation.

The environmental changes leading to black shale formation and the differences in the amplitude of these changes are explained through a model invoking monsoonally driven alterations in evaporation/precipitation and temperature patterns. The intensity of humidity and temperature increases controlled whether black shales developed on a regional or supraregional scale. The supraregionally distributed Niveau Paquier formed under extremely humid and warm conditions when monsoonal intensity was strongest and, as a result of increased humidity, low-latitude deep water formation was diminished. The regionally distributed Niveau Kilian formed under less increased humidity and warmth, with low-latitude deep water formation being reduced to a lesser extent and/or on a regional scale only. The threshold for the formation of a supraregional black shale was not reached.

PLANT DNA IN PREHISTORIC COPROLITES: EVIDENCE OF DIET OR CONTAMINATION

K.J. REINHARD

School of Natural Resource Sciences, 214 Bessey Hall, University of Nebraska – Lincoln, NE 68588-0340, USA

S.A. de MIRANDA CHAVES, A. IÑIGUEZ

Fundação Oswaldo Cruz - Escola Nacional de Saúde Pública (ENSP) - Departamento de Endemias Samuel Pessoa, Rua Leopoldo Bulhões 1480, térreo - Manguinhos. Cep 21041-210 Rio de Janeiro - RJ, Brasil

DNA from Hinds Cave coprolites dating to more than 2,000 years ago included chloroplast DNA sequences.  The chloroplast sequences were interpreted as evidence of diet.   We analyzed 19 Hinds Cave coprolites to evaluate the potential sources of the chloroplast DNA.  Using the latest applications of phytolith analysis and pollen concentration, we determined that many of the chloroplast sequences are likely contaminants from ambient pollen.  We then propose a methodology of excavation and analysis that will increase the utility of molecular methods applied to the reconstruction of diet and environment in ancient times from coprolites.

COMPARISONS OF THE JURASSIC PALYNOMORPH RECORD IN THE NORTHERN HEMISPHERE ANDS AUSTRALIA

J.B. RIDING

British Geological Survey, Keyworth, Nottingham NG12 5GG, UK

The Jurassic dinoflagellate cyst records in the Northern Hemisphere and Australia and surrounding regions exhibit certain incoherencies.  The ranges of some cosmopolitan taxa are apparently significantly different.  For example, the range top of Rigaudella aemula is significantly younger in Australia than in Europe.  It is likely that palaeogeographical and/or palaeolatitudinal factors, rather than reworking, may explain some of the disparities.  Long-range macrofaunal correlations are more problematical than palynological ones because molluscs exhibit much more endemism than palynomorphs and other microfossils.  Approaches other than standard species range analysis may prove useful to global correlations; these include statistical methods of assemblage characterisation and geochemical dating.

The principal areas of similarity and disparity are analysed in this assessment of the existing literature.  The basic units analysed are the constituent biozones in the four Mid Triassic to Valanginian Superzones of Helby and others (1987), the standard Australian palynological zonation.  The Shublikodinium Superzone (Anisian-Pliensbachian) is characterised by low diversity dinoflagellate cyst associations.  Despite the presence of endemic Australasian forms, several key bioevents allow a good correlation with Europe.  For example, the Rhaetogonyaulax rhaetica Interval Zone in Australia is deemed to be of late Rhaetian age due to the abundance of the index species; also the top of the Superzone is interpreted as being earliest Sinemurian, rather than Pliensbachian.  The overlying Luehndea-Susadinium? Assemblage is a low-diversity early Toarcian dinoflagellate cyst assemblage which was developed in marginal marine conditions and probably reflects the early Toarcian eustatic rise.  In the early Bajocian to late Callovian Pareodinia ceratophora Superzone of Australia, all the constituent zones appear to be considerably older than the ages originally suggested, based on European dinoflagellate cyst datums.  The most reliable macrofossil tie point occurs in the lowermost part of this Superzone.  This is the molluscan fauna of the Newmarracarra Limestone of Western Australia, which is early Bajocian in age and the dinoflagellate cyst floras of the Dissiliodinium caddaense Oppel Zone are consistent with this interpretation.  The development of the major dinoflagellate cyst lineages at this time appears to be similar worldwide.  The three zones of the Oxfordian Pyxidiella Superzone and the lowermost five zones of the late Oxfordian to Berriasian/Valanginian Fromea cylindrica Superzone are also interpreted to be older than originally envisaged.  Hence this trend is a consistent one.  However, the uppermost four zones of the Fromea cylindrica Superzone are deemed to be of similar ages to those originally assigned to them.  Endemism is at its greatest during the Fromea cylindrica Superzone; this is a result of the generally regressive eustatic regime at this time.

PALYNOSTRATIGRAPHIC AND GEOLOGICAL SETTING OF THE LATE OXFORDIAN – EARLY VOLGIAN FULMAR FORMATION RESERVOIR OF THE JANICE FIELD (BLOCK 30/17A, UK NORTH SEA).

L. RILEY

BVR International Ltd, 64 South Street, Epsom, Surrey, KT18 7PH, UK

Kerr McGee North Sea (U.K.) Ltd, Ninian House, Altens, Aberdeen AB12 3LG, UK

BVR International Ltd, 64 South Street, Epsom, Surrey, KT18 7PH, UK

Kerr McGee North Sea (U.K.) Ltd, Ninian House, Altens, Aberdeen AB12 3LG, UK

The Upper Jurassic fairway of the southwest Central Graben has proven to be a prolific oil-producing area since the initial discovery of the giant Fulmar Field by Shell UK in 1975.  Subsequent significant discoveries include BP’s Clyde Field and satellites (Leven and Medwin) and Talisman operated Halley Field (formerly Amoco). The Janice Field, located in block 30/17a, was initially discovered by Phillips Petroleum in 1990 and is the latest commercial find in this area of the Central Graben. Operatorship of the field was transferred to Kerr McGee North Sea (U.K.) Ltd. in 1995 for appraisal and development.

Hydrocarbons are principally trapped within combination structural/stratigraphic traps located on a series of fault terraces, which form the western margin of the Central Graben. The main reservoir comprises very fine to medium-grained bioturbated shallow marine sandstones of the Fulmar Formation which, within the field area are well dated palynologically as Late Oxfordian through Early Volgian (J54? – J66A).  Reservoir seal is provided by the Kimmeridge Clay Formation (J66B – J76), which is also the hydrocarbon source, and the Late Cretaceous Chalk Group where the reservoir is truncated by the base Cretaceous unconformity.

Palynostratigraphic criteria allow for the division of the Janice Field Fulmar Formation into four broad layers, based on major marine flooding surfaces that correlate directly to Partington et al.’s (1993) "J Sequence" events: In ascending stratigraphic order; Paralic Unit (?J54), Lower Fulmar (J62), Middle Fulmar (J63) and Upper Fulmar (J64 – J66A). Ongoing revisions to the palynostratigraphic framework during the course of appraisal drilling have subsequently modified the field model and intra-field well correlations by for example removing the major "Upper", "Middle" & "Lower" Fulmar thickness changes as originally maintained between wells 30/17a-10, 30/17a-11 in the 1987 Annex B application.  This revised reservoir stratigraphy, initially based on the palynostratigraphic database, has been further refined and it now allows for the recognition of 15 genetic units.  The current field model maintains a correlative subdivision of the Fulmar Formation reservoir into theoretical  "flow units", separated by low permeability zones (baffles) and/or barriers, whilst still maintaining the overall palynostratigraphic integrity.

Janice Field stratigraphy is also reviewed in a regional stratigraphic/ geological setting as part of an on going regional Upper Jurassic prospectivity study. The Late Oxfordian – Early Volgian Janice Field Fulmar Formation reservoir is demonstrated as being part of an overall southwards younging (Middle Oxfordian – Early Valanginian) back-stepping package of genetically stacked shallow marine sandstones, which relates to on going phases of fault-related Late Jurassic – earliest Cretaceous extension.

TERTIARY PALYNOLOGY OF NON-MARINE SEDIMENTS, MUGLAD BASIN, SUDAN

D.T. STEAD

Wellstrat Services Ltd., 51 Kirkett Avenue, Higher Kinnerton, Flintshire, CH4 9BN, UK

Greater Nile Petroleum Operating Company, P.O. Box 479, Hotel Palace, Khartoum, North, Sudan

The Muglad Basin is part of the Central and West African Rift System that started to develop during late Jurassic/ early Cretaceous time. The system evolved through three rift cycles spanning Neocomian to Cenomanian, Coniacian to Maastrichtian and Palaeocene to Pliocene. In this work the results of a palynological study of selected wells from the Muglad Basin, Sudan are presented.  These wells, Amal –1 and May 25^th, together, allow for palynological analysis of a nearly complete Tertiary section (Quaternary to Palaeocene) which was developed during the last rift cycle.  Five Zones have been recognised, most of which are further divided into two sub-zones.  The Zones are (i) Graminaceae – Chenopodipollis microporatus (Quaternary; Post-Adok Formation); (ii) Verrucatosporites spp. (Pliocene – Miocene; Adok Formation); (iii) Cyathidites minor – Perfotricolpites digitatus (Miocene – Oligocene; Tendi Formation); (iv) Striatopollis spp. (Oligocene – Eocene; Nayil Formation); (v) Mauritiidites crassiexinus – Echimonocolpites rarispinosus (Palaeocene; Amal Formation).  The characteristics of each zone and corresponding sub-zones are discussed.

COMBINED RESERVOIR-SCALE PALYNOSTRATIGRAPHY AND d¹³C_org STRATIGRAPHY FOR EARLY PERMIAN OIL-BEARING GLACIGENE ROCKS IN OMAN

M.H. STEPHENSON

British Geological Survey, Keyworth, Nottingham, NG12 5GG, UK

National Isotope Geoscience Laboratory, Keyworth, Nottingham, NG12 5GG, UK

P.L. OSTERLOFF

Petroleum Development Oman, PO Box 81, Muscat 113, Sultanate of Oman

Palynological study of the Early Permian Gharif and Al Khlata Formations of Oman has allowed a high-resolution biozonation based on the microfloral changes occurring during a period of deglaciation after the Permo-Carboniferous glacial episode. The biozonation enables correlation to within a few meters within fields, and to within a few tens of metres between fields. This represents a great increase in precision over previous schemes and is the most precise palynozonation yet developed for Permian clastic rocks.

A parallel study of d¹³C_org (kerogen) of palynological samples has shown that many of the palynological events are reflected in the stratigraphic d¹³C_org signature. The d¹³C_org  trends mark changes in gross plant types, though a more subtle secular d¹³C_org  variation related to climate change and Permian global warming is also probably present. The signature can be used, on a reservoir scale to corroborate palynological trends and may allow correlation where palynological samples have sparse pollen/spore yield.

The biozonation covers a period within the Asselian and Sakmarian stages of the Early Permian and utilises both quantitative changes and first and last appearance datums. In addition, the nature of some of the palynological and isotopic events allows correlation with the new sequence stratigraphic scheme developed for the Arabian Plate by Sharland et al. (2001). One of the events probably represents a eustatic deglacial relative sea level rise and as such is an important datum for correlation across the Early Permian of Gondwana.

SECULAR CHANGES IN MARINE ECOSYSTEMS MAY DRIVE PLANKTON EVOLUTION

P.K. STROTHER

Weston Observatory, 381 Concord Road, Weston MA 02493 USA

Recent research in marine geochemistry and earth systems history indicates that the chemistry of the world’s oceans has not been constant over time. Taxon diversity trends in fossil organic-walled phytoplankton (OWP) track these large-scale cycles in seawater chemistry more closely than benthic marine invertebrate taxon diversity.  (The record of nekton, on the other hand, does appear to correspond to OWP diversity, especially with respect to the terminal Devonian extinction.) This suggests that benthic marine invertebrates are, to a large extent, trophically buffered from the phytoplankton, and recent discoveries of increasing complexity in marine microbiology support this idea. If shifts in the availability of Mg, Ca, and HCO₃^- affected the evolution of the phytoplankton, then the Phanerozoic decline in atmospheric pCO₂ may have affected phytoplankton evolution as well. This is because surface concentration of dissolved CO₂ is in equilibrium with the atmosphere. Phytoplankton groups vary in their range of Rubisco efficiencies and carbon concentration mechanisms . These factors effectively determine the ability of phytoplankton to assimilate carbon.  Falkowski and Raven have demonstrated that phytoplankton have progressively evolved more efficient Rubisco over time.  Thus, the phytoplankton of both Paleozoic and Mesozoic seas may have evolved more in response to CO₂ availability than limiting nutrient (N and P) availability.

It is now imperative to take into account secular changes in both ocean water and atmospheric chemistry, when examining the geologic history of the plankton and the trophic structure of former oceans. The (rather pervasive) notion that the plankton, when viewed over geologic time, responded primarily to sea level and/or N and P availability could be too narrow a view of the range of extrinsic factors that have actually driven evolution in marine ecosystems. The evolutionary response of phytoplankton to declining CO₂ over Phanerozoic time is a new model for explaining the differences between the phylum-level composition of Paleozoic and Mesozoic seas.

THE IMPORTANCE OF DINOFLAGELLATE CYSTS IN TURBIDITE STRATIGRAPHY: CASE STUDIES FROM THE LOWER CRETACEOUS AND TERTIARY OF THE TETHYAN REALM

ENI S.p.A., Agip Division, P.O. Box 12069, 20100 Milan, Italy

Turbidite successions of the Mediterranean area have often yielded scarce and/or discontinuous recovery of foraminifers and calcareous nannofossils, the main tools used in the Italian academies for traditional biostratigraphic investigations in this kind of sediments. Accordingly, age and position of several turbidite formations in the regional stratigraphic framework and related paleogeodynamic models for the Alps/Apennines orogenic system, have always been much-debated questions.

Three case histories are presented in which the study of palynological assemblages recovered from turbidite suites cropping out in Tunisia and Italy led to unambiguous age assessments with unprecedented precision, thus enabling regional correlations. In all three cases the dinoflagellate cyst zonation schemes defined by Dutch scientists during the last decade in bio- and magnetostratigraphically calibrated pelagic sequences of the Mediterranean region, were successfully applied.

1) The composite dinoflagellate cyst zonation of Wilpshaar et al. (1996), spanning the latest Eocene-Early Miocene interval, was applied to the northern Tunisia Numidian Flysch, whose basal portion is dated as earliest Oligocene (A. diktyoplokum-R. actinocoronata zones), thus definitely older than previously inferred on the basis of scarce foraminiferal faunas. Moreover, lateral relations instead of vertical ones are documented for the first time among the Zouza, Kroumirie and Babouch members as a consequence of the role played by lateral variations of sedimentary facies during the Oligocene and the Early Miocene.

2) All the key events defining the four dinoflagellate cyst zones established by Brinkhuis & Biffi (1993) in the lowermost Oligocene at the Massignano section (GSSP of the Eocene/Oligocene boundary) were recorded in the Tusa Tuffite Formation of southern Italy. Here calcareous nannofossils provide perfectly consistent information. Therefore, younger ages, questionably inferred by some workers on the basis of poor foraminiferal assemblages, have to be rejected. A regional correlation is drawn with other circum-Mediterranean Lower Oligocene volcaniclastic turbidites, supporting the existence at that time of a unique volcanic arc in the Alps/Apennines orogenic system.

3) Exceptionally rich and well preserved palynological assemblages allowed for the first time the precise age assessment of the Monte Soro Flysch of Sicily. The zonation scheme established by Leereveld (1997) for the Lower Cretaceous of the western Mediterranean is proved as a valid reference for the stratigraphic interpretation of the dinoflagellate distribution in this unit.

DINOFLAGELLATE BIOSTRATIGRAPHY AND BENTHIC FORAMINIFERS FROM THE RUPELIAN/CHATTIAN BOUNDARY IN NW BELGIUM: TOOLS TO EXPORT THE STAGE BOUNDARY OUT OF THE NORTH SEA BASIN?

S. VAN SIMAEYS, E. DE MAN

University of Leuven, Lab Stratigraphy, Redingenstraat 16, 3000 Leuven, B

H. BRINKHUIS

University of Utrecht, Lab Palaeobotany and Palynology, Budapestlaan 4, 3584 CD Utrecht, NL

In order to define a suitable Global Stratotype and Section Point (GSSP) for the Rupelian/Chattian, or Lower/Upper Oligocene boundary, it is primordial to recognize and characterize biotic change associated with the unit-stratotypes, both defined in the southern North Sea Basin. The Rupelian was defined by Dumont (1849) based on the Boom Clay outcrops along the rivers Scheldt and Rupel in NW-Belgium; Anderson et al. (1971) selected the Doberg near Bünde (Westfalen, Germany) as Neo-stratotype for the Chattian Stage.

Currently, the Rupel/Chattian boundary based on the LAD of Chiloguembelina cubensis at the top of planktonic foraminifer Zone P21 a, is considered to fall within magnetochron C10n.1n, at ~28,5 Ma (Berggren et al., 1995).

As clarified in Berggren et al. (1995) the Cenozoic time scale integrates an extensive DSDP/ODP record of planktonic foraminifera and calcareous nannofossil biostratigraphy from relative stable marine environments at low-latitudes. Because of the mid high-latitude position of the North Sea Basin, and notably its enclosed palaeogeography, calcareous microfossil correlations with international zonation schemes appear problematic for the critical interval. Nevertheless, notably benthic foraminifers are quite useful for regional correlation. The earliest layer of the Chattian sequence is locally known as the Asterigerina Horizon, named after the bloom of this benthic foraminifer, and the FAD of Elphidium subnodosum and Protelphidium roemeri (Gramann & Spiegler, 1986).

Dinoflagellates seem to be less affected by latitudinal variations and occur in shallow as well as in deep marine settings. A selection of dinoflagellate events from the upper part of the Rupelian type locality, compared with the results of ongoing studies on sections from the same interval in central Italy (OLIS project) allow detailed interregional correlation.

From geophysical investigations of several boreholes in the north of Belgium (Vandenberghe et al., 2001) it became clear that twice as much Boom clay is present in the Campine subsoil, of which only the lower half corresponds with the outcrop section, studied on dinoflagellates by Stover and Hardenbol (1994).

The cored Weelde and Mol-1 boreholes cut through this unstudied upper part of the Boom clay and were sampled in such way that our lowermost samples clearly overlap with the topmost samples of Stover and Hardenbol (1994). Besides we also investigated the Late Oligocene Voort sands and restudied the Chattian type material from the Doberg section.

In the studied boreholes the Asterigerina Horizon is encountered; this level coincides with the first occurrences of the dinocysts Pentadinium imaginatum, Artemisiocysta cladodichotoma and Svalbardella sp. Shortly above this interval Apteodinium emslandense has its first occurrence and Achilleodinium biformoides its last. The first occurrence of Distatodinium biffii is well below the Asterigerina Horizon. These preliminary results match the available data from the Tönisberg profile, northwest Germany (Benedek, 1972). Some of these species may have the potential to be interregional markers and will play an import role in the discussion whether the planktonic foraminifer Chiloguembelina cubensis does or does not coincides with the base of the Chattian Stage?

PROGRESS IN MODELLING THE JURASSIC – CRETACEOUS BOUNDARY USING PALYNODATA AND PALYNOPLOT

J.M. WHITE

Natural Resources Canada, Geological Survey of Canada, Calgary, Alberta, T2L 2A7

An experimental model of the palynological record of the Jurassic-Cretaceous boundary was made using palynomorph occurrence records from Palynodata, a global palynological database abstracting taxon, age and locality records from over 20,000 pieces of literature. A taxon’s distribution can be visualized by Palynoplot software, which bins and plots literature records by time and modern latitude, yielding an approximation of the "real" time/space distribution of the fossil.   Plots reveal temporal and latitudinal distribution patterns, as well as potential taxonomic and data problems, such as outliers and inconsistent taxonomy. The concentration of palynological studies in northern mid- latitudes, especially Europe, is evident. Hence, patterns are weighted to the standards of those areas.

Genera were chosen for the experiment because: there is more agreement amongst palynologists about the characteristics of these genera than their species; the data are more abundant, hence less noisy; and working with few taxa greatly simplifies the interpretation. Citation abundance results are a "consensus view", reflecting both population central tendency and variation in the distribution of a taxon. This differs from and complements the "type section" view. Genera which are recognized as showing useful patterns of change through Late Jurassic and Early Cretaceous time are Appendicisporites, Cicatricosisporites, Contignisporites, Crassitudisporites, Impardecispora, Ischyosporites, Klukisporites, Pilosisporites and Trilobosporites.

Many genus plots show abrupt increases in abundance from the Jurassic to the Cretaceous. Without evidence of rapid environmental change, one might anticipate a more gradual transition. Hence, the abruptness of the change may be an artifact of the nature of biostratigraphic inference. The "real" J-K boundary may be somewhere in what is recorded as Early Cretaceous.

The northern mid-latitude dominance in study density makes it difficult to compare patterns amongst genera in the time/latitude matrix. Comparison is facilitated by converting each of the selected genera to a proportion of their sum for each time/latitude bin. As proportions, the data are comparable between genera. The zones of higher data density become areas of higher confidence. The proportional data can be visualized using GIS software, which facilitates pattern recognition. Plots show that the ratio Appendicisporites  + Cicatricosisporites/ Klukisporites + Ischyosporites increases across the boundary. These results are promising but need refinement. Could this or other ratios be used to provide a palynostratigraphic standard for the Jurassic-Cretaceous transition?  Could they be calibrated by comparing the results with data from reference sections?

DIVERSITY IN MORPHOLOGY AND FUNCTION OF SPORES FROM THE EMSIAN (LOWER DEVONIAN)

V. WILDE, R. BROCKE

Forschungsinstitut Senckenberg, Palaeobotanik, Senckenberganlage 25, 60325 Frankfurt/Main, Germany

Göttinger Zentrum Geowissenschaften, Geobiologie, Goldschmidtstraße 3, 37077 Göttingen, Germany

Associations of spores from the Emsian (Lower Devonian) and lowermost Eifelian (Middle Devonian) of the Eifel Hills and the Middle Rhine area (Rheinisches Schiefergebirge, Germany) have been studied palynologically. Due to the high degree of thermal maturity in the organic matter from the study area, IR microscopy was successfully applied. Special attention was paid to trends in the evolution of spore morphology and their potential functional meaning.

Spores around the Lower/Upper Emsian boundary are still characterized by comparatively small size and simple sculpture, whereas size and morphological diversification increase significantly within the Upper Emsian and into the Eifelian.

Most obvious trends are:

1. A considerable increase in size in some of the taxa which may be related to heterospory.

2. An increase in complexity of ornamentation and exine thickness, possibly related to mechanical resistance to transport/distribution or protection against drying up.

3. Evolution of saccus-like structures, potentially related to aerial transport and/or incipient gymnospermy.

Altogether, these trends may have been related to major steps in the evolutionary diversification among early land plants throughout the Emsian as reflected by palynological results from the Rheinisches Schiefergebirge.

FORTIES FIELD: THE APPLICATION OF BIOSTRATIGRAPHY TO A MATURE FIELD

G. WILLIAMS

GeoStrat Ltd., Dalziel Street, Motherwell ML1 1PJ, Scotland, UK

BP Exploration Operating Company, Farburn Industrial Estate, Dyce, Aberdeen AB21 7PB, Scotland, UK

Biostratigraphic studies have been carried out on the Forties Field throughout the field life.  The current study has taken this work forward with extensive new palynological analyses and a change in emphasis from the Forties Main Sand that has dominated earlier stratigraphic interpretation, to the younger sands in the upper part of the Forties Sandstone Member where much of the remaining hydrocarbons are to be found.

The approach taken in this study emphasizes a holistic approach to the taxonomic groups used, using dinocysts, prasinophycean algae, pteridophyte miospores, angiosperm pollen, reworking events and taxa of unknown affinity.

A total of forty-one bioevents have been recognised from the dataset of which eleven are considered to be the most reliable.  These events have been recognised elsewhere in the Forties fan system, e.g. Arbroath, Montrose.

These events reflect a combination of extinctions, inceptions, acmes, subregional palaeoenvironmental changes and local palaeoenvironmental events.  These latter events reflect the affects of a number of drivers including tectonism, flooding events, climate and the progradation of the fluviodeltaic system which fed sediment into the Forties fan.  These relationships are interpreted in relation to regional sequence stratigraphic events.

The stratigraphic resolution achieved has been integrated into seismic interpretation and sedimentological interpretation to constrain the architecture of sands within the upper part of the Forties Sandstone Member.

This greater understanding has allowed better definition of remaining unproduced hydrocarbons and provided a robust biostratigraphic scheme to assist in the drilling of infill wells to tap these accumulations.

NON-ACID WELLSITE PALYNOLOGY: WIDENING OPPORTUNITIES

G. WILLIAMS, P. WATSON

GeoStrat Ltd., Dalziel Street, Motherwell, Lanarkshire ML1 1JP, Scotland, UK

BP Exploration Operating Company, Farburn Industrial Estate, Dyce, Aberdeen AB21 7PB, Scotland, UK

GeoStrat Ltd., Dalziel Street, Motherwell, Lanarkshire ML1 1JP, Scotland, UK

BP Exploration Operating Company, Farburn Industrial Estate, Dyce, Aberdeen AB21 7PB, Scotland, UK

Wellsite palynology is an established geoscientific tool, which involves the ‘real time’ preparation and analysis of samples from the subsurface.  Analysis of the palynomorphs in these samples during drilling is used to identify the location of the drill bit in the geological succession, critical for reservoir prediction, enabling crucial decisions including biosteering, casing, coring and terminal depth calls to be made.

Until recently extraction of the palynomorphs was only considered possible with the use of highly toxic and hazardous chemicals (e.g. hydrofluoric acid) and technical support in a mobile laboratory, resulting in high costs, logistical problems and HSE risk.  Developments made by GeoStrat Ltd. have removed the bulk of the chemical component in the sample processing and allow a primarily mechanical extraction technique to be employed at the wellsite, a major breakthrough, which reduces cost and logistical problems and virtually eliminates any chemical HSE risk.  As a result, the application of wellsite palynology has expanded, operational costs at wellsite have been reduced, the dependence on a limited market place for the hire of specialised laboratory equipment is eliminated and the global reach and potential of this technique is enhanced.

The technique has been used successfully at wellsite for sediments of Tertiary to Middle Jurassic age, whilst laboratory testing has shown a wide geographic and age applicability.

BP has formed a strategic alliance with GeoStrat to use this technique and has applied it to over 30 wells in offshore UK and Norway.  The proportion of wellsite palynology now undertaken utilising this technique within BP, in the UK and Norwegian offshore, has risen to over 30% and will continue to rise.

Examples of the application of the technique will be given, with particular emphasis on horizontal biosteering, maximising mature field recoverable reserves and areas with logistical limitations.

A HIGH RESOLUTION PALYNOSTRATIGRAPHIC FRAMEWORK FOR THE FLUVIAL-LACUSTRINE PATCHAWARRA FORMATION, COOPER BASIN, SOUTH AUSTRALIA

G.R. WOOD, P.C. STRONG

Santos Limited, 91 King William Street, Adelaide, South Australia 5000

Fluvial-lacustrine reservoirs in coal-bearing strata provide a particular challenge for reservoir characterisation because of the dominance of coal on the seismic signature and the highly variable reservoir geometry, quality and stratigraphic connectivity. The development of flow unit scale geological models for the fluvial gas reservoirs in the Permian Patchawarra Formation of the Central Australian Cooper Basin are critical to minimise the perceived reservoir risks of these relatively deep targets.  A multidisciplinary team was formed to integrate recently acquired 2D and 3D seismic data to the geology using high-resolution sequence stratigraphic concepts to constrain depositional environments and thus provide a better tool for predicting reservoir distribution. An improved model required the construction of a robust regional chronostratigraphic framework as a starting point, constrained where possible by palynostratigraphic control. The framework has been developed by identifying key surfaces, primarily unconformities, regional lacustrine flooding surfaces represented by high gamma ray shales, or climatically and tectonically controlled periods of clastic shutdown represented by regionally extensive coal. It was important to define the regional chronostratigraphic significance of these surfaces in order to extend the scheme more confidently to areas of high heat flow where palynostratigraphic control was poor.

The chronostratigraphic framework utilised has been built around improvements to the palynostratigraphic scheme for Eastern Australia together with the definition of an additional series of events specific for the Cooper Basin. This refined Cooper Basin spore/pollen event stratigraphy is of sufficient resolution to provide control for the twelve regionally correlatable markers and eighteen local horizons. Two major unconformities within the Patchawarra Formation divide the section into three mega sequences. The recognition of these tectonically enhanced sequence boundaries in conjunction with the higher resolution palynostratigraphic control has permitted the delineation and correlation of chronostratigraphically significant surfaces with confidence.

The chronostratigraphic framework defined has allowed detailed palaeogeographic mapping to be carried out at flow unit scale. For specific horizons, palaeogeographic reconstructions were produced by an iterative process between the detailed log analysis, sedimentology and fine-scaled seismic mapping. These maps are drawn with the guiding control of syn-depositional structural features and net/gross trends, using structure and isochron maps from the seismic interpretation.

PALYNOLOGICAL ANALYSIS OF MYOTRAGUS BALEARICUS COPROLITES – THE EXTINCTION OF ANIMAL AND VEGETAL SPECIES DURING THE HOLOCENE IN THE BALEARIC ISLANDS (SPAIN)

R. YLL, R. PÉREZ-OBIOL

Departament de Biologia Animal, Biologia Vegetal i Ecologia, Unitat de Botànica, Universitat Autònoma de Barcelona, 08193 Bellaterra, Barcelona, Spain

Institut Mediterrani d'Estudis Avançats (CSIC-UIB), Cta de Valldemossa km 7,5, 07071 Ciutat de Mallorca, Balears, Spain

The Balearic Islands are located in a very critical biogeographic position with respect to the oscillations that dominated the climate during the Quaternary. The study of the evolution of the landscape in these islands shows that the processes of change have been more evident in comparison with the continent. A radical change of the landscape registered during the Holocene implied the medium term disappearance of some vegetal and animal species. The extinction of Hypnomys morpheus, Nesiotites hidalgo and, specially, of Myotragus balearicus are well documented. Myotragus balearicus was a ruminant exclusive of the Balearic Islands. The first human inhabitants settled in the Balearic Islands coexisted with Myotragus until the species became extinct, at about 4,000 years ago. The unusual morphology of Myotragus balearicus has originated speculations on its diet.

The fact that Myotragus balearicus lived under insular conditions implies that particular adaptations to the pre-human environments have been done. Likewise, Myotragus balearicus has been played an important role within the insular ecosystems of the Balearic Islands and could be related with the evolution and the transformation of the Balearic flora.

Coprolites of Myotragus balearicus have been collected during several excavation campaigns and palynological analyses were carried out. Pollen analyses reveal that Buxus balearica (a toxic plant) was involved in the habitual diet of Myotragus balearicus, being a source of great importance. Buxus balearica was an abundant pant in the landscape until the mid Holocene and, afterwards, reduced its presence dramatically. This fact could have been related with the cause of the reduction of its presence in the Balearic Islands. It is difficult to assign a simple causal relation between the extinction of Myotragus balearicus and this plant. In addition, this disappearance is produced synchronically with the abrupt climatic change registered in the Mediterranean during the V millennium BP and with the expansion of the human presence in the Balearic Islands. These considerations open a debate that must consider the relation between this extinction and their explanation from climatic or anthropic causes.

POSTER ABSTRACTS

PALYNOLOGICAL INVESTIGATION OF THE UPPER SILURIAN (ACACUS FORMATION) OF WELL A1-NC40B, GHADAMES BASIN, NORTH WEST LIBYA

F. ABUHMIDA, A.A. EL HARBI

Petroleum Research Center, P. O. Box 6431 Tripoli, Libya

Twenty conventional core samples from the Acacus Formation of Well A1-NC40B from the Ghadames Basin, Libya have been analysed for their palynological content. They yielded well preserved and diverse marine and nonmarine palynomorphs, with a hundred and seven species of both marine and nonmarine origin. Sixty seven species of acritarchs assigned to thirty four genera, twenty two species of spores and cryptospores placed in ten genera, and eighteen species are chitinozoas accommodated into eight genera were identified. In addition scolecodonts and fresh water algae (Khafia arabica) were recognised. Two assemblages are recognised based on different palynomorph groups (marine and nonmarine). These assemblages have been compared with previously described Silurian palynomorph assemblages reported from the Ghadames Basin northwest Libya, other areas of North Africa, and other localities. A Wenlock-Ludlow age is suggested for the lower and upper assemblage of the studied section. Regarding the variation in the proportion of marine and terrestrial palynomorphs, and some sedimentological evidence, the depositional environment is interpreted as near shore shallow marine with distance to shore line decreasing with time. This interpretation is supported by the increase in the proportion of terrestrial taxa, and decreasing proportion of marine taxa upward of the studied section of Acacus Formation.

DINOFLAGELLATE CYSTS OF THE GAULT CLAY (ALBIAN) AT COPT POINT, FOLKESTONE, SOUTH-EAST ENGLAND

J. DUNN

Department of Earth Sciences, University College London, Gower Street, London WC1E 6BT, UK

Department of Palaeontology, The Natural History Museum, Cromwell Road, London SW7 5BD, UK

An investigation of dinoflagellate cysts will be undertaken on samples collected from the type section of the Gault Clay at Copt Point near Folkestone, Kent

. The standard reference bed numbers (I-XIII) of Owen (1971a, 1975), constrained using ammonite zones, provide the stratigraphical framework.

The aim of the study is to document the taxonomy and interpret changes in relative species abundance and assemblage composition. The dinoflagellate cyst associations will be related to palaeoecological parameters to determine and define any flood horizons. Such results may have a bearing on our understanding of the palaeogeographic distribution of dinoflagellate cysts during the Albian.

The quality of preservation combined with diverse and rich assemblages also makes the succession ideal for using new techniques in optical microscopy. The project is to be carried out using conventional light microscopy and confocal laser scanning microscopy (CLSM). The CLSM will be used to enhance the morphological studies of the dinoflagellate cysts.

DINOFLAGELLATE AND PALAEOMAGNETIC STRATIGRAPHY OF EOCENE TO OLIGOCENE SEDIMENTS FROM THE NORWEGIAN-GREENLAND SEA

J. ELDRETT, I.C. HARDING

School of Ocean and Earth Sciences, Southampton Oceanography Centre, Southampton University, European Way, Southampton, SO14 3ZH, UK

Ocean Drilling Program, College Station, TX, USA.

The presence of abundant age-diagnostic dinocysts at Site 913B (ODP Leg 151), Site 338 (DSDP Leg 38) and Site 643A (ODP Leg 104) has enabled the development of a new high-resolution biostratigraphy for the Eocene-Oligocene interval in the Norwegian-Greenland Sea.  This is particularly important as the calcareous microfossils usually used for biostratigraphy are generally absent in these high latitude Eocene-Oligocene sediments due to dissolution. In addition, the development of a new magnetic reversal stratigraphy for the Norwegian-Greenland Sea has enabled independent age control and allowed the dinocyst biostratigraphy to be firmly tied into the global geomagnetic timescale for this period.

The high-resolution study employed for this project has identified dinocyst assemblages that show affinities with those from the North Sea and North Atlantic, allowing regional correlation.

STATISTICAL APPROACHES TO FOSSIL DATA: ENHANCING MULTI-WELL CORRELATION THROUGH FUZZY C MEANS CLUSTERING OF TAXONOMIC DATA

S.L. GAPONOFF, S.N. NELSON

ChevronTexaco Exploration & Petroleum Technology Company,

6001 Bollinger Canyon Road, San Ramon, CA, USA 94583, USA

CNOOC China Limited, P.O. Box 501, Tianjin, China 300452

Technical Alliance for Computational Stratigraphy, Energy and Geosciences Institute, University of Utah, 423 Wakara Way, Suite 300, Salt Lake City, UT, USA

A challenge facing biostratigraphers in the petroleum industry today is the recognition and interpretation of non-discrete stratigraphic events occurring over relatively short amounts of geologic time.  The traditional biostratigraphic approach focuses on discrete stratigraphic events (e.g. origination and extinction events over long periods of geologic time).  Discrete events seldom allow high-resolution interpretations necessary for field-scale, reservoir correlations.   A combination of discrete and non-discrete events would provide the highest resolution interpretations of these data.  This poster contrasts the application of multivariate statistical methods (principal components analysis and fuzzy c-means clustering) to taxonomic data with the objective of creating high-resolution interpretations using non-discrete stratigraphic data (i.e., data vectors).

The more common approach, particularly among academics (e.g., Kipp, 1976) to multivariate analysis of fossil assemblages has been the use of eigenvector techniques, such as principal components analysis (PCA).  The objectives of eigenvector-based methods are to (1) resolve subassemblages of multiple covarying taxa; and (2) establish a set of paleoenvironmentally related curves that can be used to correlate between wells.  In industrial applications however, the promise of eigenvector-based biostratigraphic analysis remains unfulfilled.  Complications arise from the fact that paleontological data are notoriously sparse.  This is problematic for eigenvector-based methods because inversion, a mathematical requirement, of sparse matrices is often non-unique, hence unstable.  Further, if sparse taxa are deleted to meet the mathematical constraints, then stratigraphically useful markers may be arbitrarily discarded. 

Like eigenvector-based methods, fuzzy c-means clustering (FCM) is used to define subassemblages of covarying taxa, but FCM does not require matrix inversion.  The use of FCM in combination with discrete events data allows maximum stratigraphic information to be extracted from a quantitative biostratigraphic data set.  This combined multivariate/discrete approach using FCM was tested on a palynological data set from Liadong Bay, China (four wells from three different fields).  First-order stratigraphic boundaries were initially established using the standard industrial biostratigraphic approach (i.e., discrete events, such as ‘tops’).  The quantitative assemblage data were then analyzed using FCM.  Two paleoenvironmental subassemblages were resolved.  Comparing FCM results with discrete-event-derived zonal boundaries that were ambiguous could be further refined using FCM-derived assemblage curves.

UPPER CENOZOIC DINOFLAGELLATE CYST STRATIGRAPHY OF THE SOUTHERN NORTH SEA BASIN – A SYNTHESIS

M.J. HEAD

Department of Geography, University of Cambridge, Downing Place, Cambridge CB2 3EN, UK

Palaeontology Research Unit, University of Ghent, Krijgslaan 281/S8, B-9000 Ghent, Belgium

The correlation of Upper Cenozoic marine deposits across the southern North Sea basin is fraught with difficulties. The fragmentary nature of the sedimentary record and diagenetic overprinting are frequent obstacles to magnetostratigraphy. Restricted marine conditions have excluded planktonic foraminifera and calcareous nannofossils for much of the time. Pollen stratigraphy provides a generally continuous record, but offers relatively low resolution for the Miocene and lower Pliocene, and is prone to taphonomic difficulties in more offshore settings. 

Dinoflagellate cysts and marine acritarchs are shown to be a useful group for stratigraphic correlation and environmental reconstruction in the southern North Sea basin, owing to their wide salinity tolerance, high taxonomic diversity, and good preservational potential. In eastern England only the Pliocene and lower Pleistocene are represented substantially by marine deposits, and even here the record is highly incomplete. Yet more than 60 taxa are represented, and help to constrain the age of these deposits. In northern Belgium, Neogene marine deposits represent the southeastern margin of the southern North Sea Basin. These deposits are also discontinuous, but include the lower, middle and upper Miocene as well as lower and upper Pliocene. The Miocene dinoflagellate assemblages are particularly diverse and well preserved, and facilitate correlation across the North Atlantic region and as far as the US Atlantic coastal plain and shelf.  The Pliocene assemblages can be correlated with those of eastern England and into the North Atlantic. 

We present a biostratigraphic synthesis for the southern North Sea Basin, based on published and unpublished results, and attempt to reconcile the stratigraphy of this region with the sequence chronostratigraphic framework of Hardenbol et al. (1998).

ANGIOSPERMID POLLEN FROM THE MIDDLE TRIASSIC: MORPHOLOGY, BIOSTRATIGRAPHY AND POSSIBLE AFFINITY

P.A. HOCHULI

Paläontologisches Institut und Museum, Universität Zürich, Karl Schmid-Str. 4, CH-8006 Zürich, Switzerland

Palaeontology Department, The Natural History Museum, Cromwell Road, London SW7 5BD, UK

Middle Triassic sediments of the Barents Sea area contain a variety of dispersed colpate, and operculate pollen grains of angiospermid morphology. Several different pollen types can be differentiated, all from the same stratigraphic interval (Ladinian to Anisian). Due to their consistent occurrence some of them have been used as stratigraphic markers under the designation of Retisulcites sp. 1, 2 (Hochuli et al. 1989) and Retisulcites sp. A (Vigran et al. 1998).

All the described forms are characterised by well-developed semitectate reticulate sexines, which are connected by columellar structures to thin nexines (footlayer and endexine). Due to the pollen's very small size, their microscopical analysis is near the limit of optical resolution. So, in addition to high-resolution transmitted light microscopy, Confocal Laser Scanning Microscopy (CLSM) has been used for morphological analysis of the very delicate wall and surface structures. In CLSM the specimens were imaged in very thin, only ca. 360 nm thick, optical sections using fluorescence mode (excitation 568 nm, detection 590 nm LP). The optical sections were subsequently re-composed to generate extended focus images and 3D computer models.

Pollen grains of comparable morphologies are common in sediments of Early Cretaceous age (Aptian / Albian). For the Middle Triassic all these pollen types are new, some of them show resemblance to the forms described by Cornet (1989) from the Carnian of the Richmond Basin (VA, USA). In the Barents Sea area the consistent occurrence of these angiospermid pollen shows that the producing (mother) plants were widely distributed and their diversity suggests that several species were involved.

Among modern angiosperms reticulate, monocolpate pollen are generally associated with magnoliid affinity, however, it cannot be excluded that these pollen represent a so far unknown group of gymnosperms which produced pollen of angiospermid morphologies.

ACRITARCH BIOSTRATIGRAPHY OF THE DEVONIAN OF THE APPALACHIAN BASIN, AND ITS CORRELATION WITH ESTABLISHED SPORE ZONES AND U-Pb ZIRCON-DATED ASH BEDS

G.M.G. HUGHES, K.T. HIGGS

Dept. of Geology, University College Cork, Cork, Ireland.

Palynological samples have been collected from Devonian sequences in the Appalachian basin of the U.S.A., ranging from the Emsian to the early Fammenian. The sample localities include sites in Tennessee, Virginia, West Virginia and N.Y.State.

Many of these sequences include U-Pb zircon-dated ash beds (Tucker et al., 1998), and all are being systematically studied to establish assemblages and ranges for acritarchs and prasinophytes. Additionally, the spores are being used to correlate the sedimentary sequences and marine palynomorphs with existing spore zonation schemes.

Results are presented here as an inter-correlation between sedimentary sequences, marine palynomorphs, spore zones and radiometric dates.

DINOFLAGELLATE CYST AND FORAMINIFERA BIOSTRATIGRAPHY OF THE CALLOVIAN TO VOLGIAN REFERENCE SECTION IN THE TYUMEN SUPER-DEEP WELL SD-6 (WEST SIBERIA, RUSSIA)

V.I. ILYINA, B.L. NIKITENKO, L.A. GLINSKIKH

Institute of Petroleum Geology, Siberian Branch of RAS, 630090, Novosibirsk, pr.Ac. Koptyuga, 3, Russia

The Tyumen super-deep well SD-6 penetrated to the Triassic and Jurassic sediments is located in Urengoy region on the north of West Siberia . The Callovian to Upper Jurassic part of this section (about 200 m) drilled with almost continuous recovery of core from Vasyugan, Georgiev and Bazhenov Formations includes rich and diverse microfossil assemblages. It is the Callovian to Upper Jurassic reference section in West Siberia and a unique object for development of detailed biostratigraphy based on foraminifera and dinoflagellate cyst data. A complex layer-by-layer study of systematical composition and stratigraphical distribution microfossils permitted to establish the successions of dinoflagellate cyst and foraminifera assemblages from the Callovian to Volgian as a basis for the biozonation. The distinctive features of microfossils associations reflecting biofacies have been studied. The main regularities of distribution of microfossils depending on the changes of transgressive - regressive events and paleoenvironments in Callovian - Late Jurassic have been established. Zonal biostrata of Jurassic regional foraminifera scale of Siberia calibrated according as the Uppermost Bathonian-Callovian and Lower Oxfordian in this section have been traced. Nearly continuous sequence from the nine dinozones and beds with dinocysts in a uniform section of the Lower Callovian to Middle Volgian has been established for the first time. The FAD and LAD events of stratigraphical significant dinocyst taxa and acme of selected species served as criteria of the establishment of dinostrata. Dinozone Fromea tornatilis is erected for the lowermost Callovian as well as on the Russian platform (Zones Falsum and Puzhmae). The top of Zone coincides with the upper boundary of Beds with foraminifera Kutsevella memorabilis-Guttulina tatarensis. Beds with Impletosphaeridium spp.-Lagenadinium callovianum have been defined as preliminary dinostraton for the upper part of Lower and Middle Callovian. Two dinozones in the Upper Callovian have been recognized. These are Gonyaulacysta jurassica subsp. adecta var. longicornis (equivalent to Pareodinia prolongata Biozone of Russian Platform) and Wanaea thysanota calibrated according as ammonite Zones. The base of Dinozone Wanaea fimbriata erected for the Lower Oxfordian is panboreal mark level between the Callovian and Oxfordian in different regions of northern Europe and West Siberia. Dinozone Rigaudella aemula is defined within the Middle and Upper Oxfordian. The top of Zone approximately coincides with the upper boundary of foraminifera Zone Recurvoides disputabilis in the uppermost Oxfordian. Dinozone Rhynchodiniopsis cladophora for the Kimmeridgian  (= the Lower Kimmeridgian sensu anglica) without uppermost beds have been recognized. The letter is recovered by Beds Amphorula delicata-Cribroperidinium spp., the top of which is defined by the FAD of Oligosphaeridium patulum approximately in the base of the Middle Volgian.

THE PALYTECH "SIEVE-O-MATIC" – AN AUTOMATED SYSTEM FOR SIEVING & WASHING PALYNOLOGICAL SAMPLES

Palytech Processing Ltd, 77 Market St, Birkenhead, Wirral, CH41 6AN, UK

Over the last 2 years a stand-alone filtration system/work station has been developed and tested on thousands of industrial and academic samples. The system eliminates the drudgery, tedium & frustration associated with sieving palynological samples, which can often lead to reductions in sample quality and staff productivity.

The system allows 8 samples to be sieved simultaneously via gentle agitation. No suction or ultrasonic vibration is used, so minimising palynomorph loss or damage. During sieving repeated dilutions are applied automatically, in order to wash samples free of chemicals and fines. The volume and number of dilutions is pre-set by the operator via an electronic keypad. The system is also programmable for operation out of hours.

Benefits:

Staff free to spend more time pursuing quality

Increased productivity

Huge savings in terms of water consumption

Sits inside an existing fumehood

Increased operator safety due to greatly reduced chemical handling

Elimination of repetitive task strain 

Portable wellsite version currently under development

INTEGRATED BIOZONATION SCHEME FOR THE LATE CRETACEOUS TO TERTIARY OF NORTH AFRICA

J.B. KEEGAN, G. COLES

Wellstrat Services Limited, 51 Kirkett Avenue, Higher Kinnerton, Flintshire CH4 9BN, UK

Datum Stratigraphic Associates Limited, 12 The Meade, Chorltonville, Manchester M21 8FA, UK

Wellstrat Services Limited, 51 Kirkett Avenue, Higher Kinnerton, Flintshire CH4 9BN, UK

Veba Oil Operations, P.O. Box 690, Tripoli, Libya

Department of Geological Sciences, University College London, Gower Street, London WC1E 6BT, UK

The application of sequence stratigraphic techniques for basinal modelling in oil exploration is playing an increasingly important role.  Biostratigraphic input for definition of sedimentary sequences is crucial for the determination of an accurate age-dating of tectonic and sedimentary events of basins and hence their precise modelling.  The thick Late Cretaceous – Tertiary sequences preserved in North African basins have yielded abundant and diverse microfaunal and microfloral assemblages.  An evaluation of the main biostratigraphic index fossils has been undertaken by reviewing published data across North Africa from Egypt to Morocco.  Range charts of stratigraphically diagnostic dinoflagellate cyst, foraminifera, nannoplankton, ostracods and sporomorph species are presented.  These range charts are based, or modified from the currently available published data.  The charts cover the Cenomanian to Pliocene intervals.  Presentation of the various microfossil groups permits age dating of both the carbonate and clastic sedimentary sequences.  An integrated biozonation scheme is presented which is tied to the sea level curve of Haq et al. 1987.  The proposed integrated scheme will permit for the first time, inter- and intra-basinal biostratigraphic correlation of the sedimentary sequences across North Africa.

PALYNOFACIES CHARACTERISTICS OF LATE JURASSIC (OXFORDIAN TO KIMMERIDGIAN) SECTIONS FROM THE SW GERMAN JURASSIC BASIN

E. LINK, M. RUF, J. PROSS

Institute of Geosciences, Sigwartstr. 10, D-72076 Tübingen, Germany

The Upper Jurassic epicontinental carbonate-marl alternations of southern Germany are characterized by multiple sedimentary cycles reaching up to 100m in thickness. As the reasons for this cyclicity are yet poorly known, a combined palynofacies/ sedimentological study has been initiated to decipher the driving factors. To date, investigations have focused on a proximal and a distal section within the SW German Jurassic Basin.

The Plettenberg quarry near Dotternhausen represents a section from the proximal part of the basin. The outcrop exhibits a small-scale interfingering of basinal facies (marl/limestone alternations) and reefal facies (sponge-rich thrombolites) of Oxfordian age.

Palynofacies assemblages are characterized by high relative abundances of terrestrial components (mainly brown and black wood, spores and pollen) and amorphous organic matter (AOM). Towards the top, the percentage of terrestrial components within the assemblages and the amount of spores within the terrestrial palynomorphs increases, suggesting a regressive trend and/or a trend to more humid conditions. This is in concert with the palynofacies signal at the Ox1/Ox2 boundary where a pronounced drop in relative abundances of chorate dinoflagellate cysts and other marine algae is observed. Highest relative abundances of marine palynomorphs occur within marly lithologies, indicating that the marls were deposited under relatively high marine influence. Hence, they seem to represent distal rather than proximal sediments. This observation is in sharp contrast to the classic view that the marls represent intervals with enhanced terrestrial influence. 

Material from the distal part of the basin is being studied from the Türkheim core. The core (Oxfordian 2 to Kimmeridgian 2.3) consists of sedimentary cycles of different orders built up by reefal facies (sponge thrombolites), intraclastic-bioclastic limestones, well-bedded limestones and shales. First palynofacies results indicate a generally higher marine influence (with high relative abundances of marine palynomorphs) as compared to the Plettenberg section. Moreover, absolute abundances of both terrestrial and marine components are higher and the AOM content is lower.

Future investigations will yield more data especially from the distal parts of the SW German Jurassic Basin. The outcome will be paleoenvironmental information that, together with sedimentological data, will aid to decipher the mechanisms responsible for the observed cycles. As a final step, the three-dimensional palynofacies relationships between different parts of the basin will be established.

DINOFLAGELLATE CYST STRATIGRAPHY AND PALAEOENVIRONMENTS OF A SHALLOW MARINE PLIOCENE SEQUENCE IN NORTHERN BELGIUM (SOUTHERN NORTH SEA BASIN)

S. LOUWYE

Palaeontology Research Unit, Ghent University, Krijgslaan 281/S8, B-9000 Ghent, Belgium

Department of Geography, University of Cambridge, Downing Place, Cambridge CB2 3EN, UK

Palaeontology Research Unit, Ghent University, Krijgslaan 281/S8, B-9000 Ghent, Belgium

The subsurface Pliocene of northern Belgium was deposited in a shallow marine environment at the southern margin of the North Sea Basin. Basal gravel lags and characteristic lithologies permitted a robust lithostratigraphic subdivision in the 1970's, but many questions remained. The construction of a biostratigraphical famework, notably with planktonic foraminifera and calcareous nannoplankton, was seriously hampered by the boreal nature of the calcareous fossils, rendering a correlation with the standard biozones difficult. Correlation with the sequence chronstratigraphic framework of Hardenbol et al. (1998) thus remained incomplete. The effects of deposition under a varying sea level regime in a marginal marine environment are clearly observed in the Pliocene sequence by distinct and rapid facies variations. Well preserved dinocyst assemblages were recovered from a Pliocene sequence in two temporary outcrops in the Antwerp harbour. Quantitative variations in the studied dinocyst assemblages reflect depth changes of the depositonal environment and cooling events.

The dinocyst assemblages from the Kattendijk Sands compare well with the assemblages recovered from the Pliocene Coralline Crag in southeast England. Thermophilic species tend to dominate and point to deposition under warm-temperate conditions in an (inner) neritic environment. Persistent presence of low numbers of  Impagidinium indicate influence of oceanic water masses in the confined depositional area of the southern North Sea Basin during Early Pliocene times. Noteworthy are biostratigraphical events such as the well constrained highest occurrences of Batiacasphaera minuta, Corrudinium devernaliae, Reticulatosphaera actinocoronata, and the occurrence of Operculodinium tegillatum, restricted to this unit. A correlation of the lower boundary of this formation with sequence boundary Me2 is proposed. The pronounced decrease of thermophilic dinocysts, together with a low species diversity in the shelly sand of the overlying Luchtbal Sands Member can probably be related to the beginning of the temperature decrease just below the Zanclean - Piacenzian boundary at 3.6 Ma, culminating in cold stages MG2 and M2 at 3.35 - 3.3 Ma. The cooling trend persists into the base of the transgressive Oorderen Sands, only higher up the unit the temperature signal compares well again to the one observed in the Kattendijk Sands. The HO of Invertocysta lacrymosa near the top of this unit indciates deposition before 2.75 Ma. A pronounced change in the dinocyst assemblage in the base of the uppermost clayey unit (Kruisschans Sands?), together with a distinct increase of pollen and reworked dinocysts, announces a shallowing of the depositional environment and a gradual cooling. However, no unconformity was observed in the field. A relationship with the cooling trend starting at 3.15 Ma and culminating in the northern hemisphere glaciation at 2.6 Ma seems apparent.

A HIGH RESOLUTION ANALYSIS OF POLLEN, SPORES AND SOME MARINE PALYNOMORPHS FROM LA PAZ BASIN, B.C.S., MEXICO

P.G. NÚÑEZ-PÉREZ, J. HELENES, L. BANDA

CICESE, División de Ciencias de la Tierra, Departamento de Geología, Laboratorio de Palinología. Carretera Tijuana-Ensenada K. 107, Ensenada, Baja California, México.

A high-resolution palynological study was carried out in 62 core samples of marine laminated sediments from the La Paz basin, Baja California Sur, México. The core was taken at a depth of 700 m, in suboxic to anoxic conditions.  Radiocarbon dates of the core indicate it contains approximately 900 years, and each sample studied represents from 10 to 20 years.  The samples were treated with the conventional palynological technique, using Lycopodium tablets for quantitative analyses.

A total of 84 species are present in this core, but only 19 are the most representative. Some of them, like Pinus murrayana, P. cuadrifolia, P. jefrey and Harfodia macroptera come from the north of the Peninsula, from Sierra San Pedro Mártir and Sierra de Juárez. Others, like Prosopis sp., Haematoxilon brasileto, Hymenoclea monogyra and most of the Graminae were transported from the La Paz Bay area. And still others, like Quercus sp., Ambrosia ambrosoides, Atriplex canescens and A. barclayana probably came from the land in the eastern side of the Gulf of California.

The most abundant pollen families were Chenopodiaceae, Compositae, Graminae, Leguminosae, Pinaceae and Polygonaceae.  The diversity was higher on the Compositae with a total of 12 species.  The abundance and distribution of the pollen families like Chenopodiaceae and Compositae are inversely proportional to Pinaceae.  This relation is probably related to temperature changes of the atmosphere and to cycles along the core.  This change is more obvious before 1311, corresponding with the Medieval Warm Period.

Marine palynomorphs like foraminifera, scolecoledonts, copepods eggs, and dinoflagellates were also observed. The most representative of these are the dinoflagellates, which are also more abundant in the samples from the Medieval Warm Period.

PALEOGENE BIOEVENTS AND SEQUENCE BOUNDARIES IN THE MACKENZIE DELTA REGION, NWT, CANADA

M.G. PARSONS, G. NORRIS

Department of Geology, University of Toronto, 22 Russell St., Toronto, Ontario, M5S 3B1, Canada

Regional tectonics exerted a major control on relative sea level change and episodes of delta-dominated sedimentation during the late Paleocene to Oligocene in the Mackenzie Delta region. The response of coastal communities and marine dinoflagellates to changing sea level recognized in outcrop sections appears to be traceable in some cases into the subsurface where four sequences are recognized – Aklak, Taglu, Richards and Kugmallit.

The late Paleocene-early Eocene Aklak Sequence has yielded predominantly terrestrial palynomorphs, but an interval of thin-walled algal cysts and Palaeoperidinium dinoflagellates has been recognized from outcrop section in the lower Aklak. The upper Aklak shows an overall increase in fungal diversity but no marine dinoflagellates in the sections examined. Distinctive Platycarya pollen appears in the western Beaufort at the top of the Aklak, but does not appear until much later in the eastern Beaufort.

The Aklak-Taglu boundary, while established in the western Beaufort, is difficult to define in the eastern Beaufort. Several palynological bioevents recognized in outcrop appear to be traceable into some of the subsurface wells and may prove useful for tagging early Taglu deposition. In the Caribou Hills, foraminifera characteristic of the Taglu Sequence precede an influx of glaphyrocystoid dinoflagellates. The dinoflagellates are accompanied by a peak in massulae of the water fern Azolla in the Caribou Hills and in Taglu G-33, where they appear to be flushed out into the marine environment in appreciable numbers during coastal flooding events. The glaphyrocystoid acme, while pronounced, is restricted to less than a metre of section and is followed by an equally short-lived deflandreoid acme. In the Caribou Hills the cyclic nature of Taglu deposition in a lower delta plain setting is evident. Marine-terrestrial shale units on the scale of ~10-20 m alternate with thick unconsolidated sands. Subsequent marine episodes record increasing dinoflagellate diversity upsection and are punctuated by terrestrial episodes with coastal vegetation supporting high diversity fungal assemblages characterized by genera such as Fusiformisporites, Punctodiporites, and Striadiporites. These and other fungal taxa flourished during the Eocene in the Delta, and many persisted into the late Eocene Richards Sequence, but are eliminated by the Oligocene, possibly due to the late Eocene/early Oligocene cooling event. The latter stages of Taglu deposition in the Caribou Hills and in a number of wells are characterized by a dominance of wetzelielloidean dinoflagellates possibly signaling estuarine conditions.

The prevalence of wetzelielloideans continues across the Taglu-Richards boundary and is accompanied by the persistence presence of Azolla in Adgo F-28, Taglu G-33 and other wells. As yet, no definite in situ marine dinoflagellates have been recognized as markers for the Oligocene Kugmallit Sequence.

SYNTHESIS OF CUAYUCA FORMATION AND CORRELATION WITH PALYNOFLORA OF BALSAS GROUP: PALEOGENE LACUSTRINE ENVIRONMENTS FROM CENTRAL OF MEXICO

Instituto de Geología, Depto. Paleontología, Laboratorio de Palinología, Ciudad Universitaria 04510, México, D.F.

Cuayuca Formation is a Tertiary basin that comprises coarse to fine alluvial deposits (conglomerates, siltstones and mudstones) and sulphate and carbonate lacustrine facies (gypsum and limestones). Fries (1966) grouped Cuayuca Fm. into three members interfingering among the siliciclastic, carbonate and sulphate lithofacies. Member "Mcc" includes siliciclastics facies from conglomerates to siltstones. In contrast, member "Mc" is characterized by limestone, chert and marl sequences. Finally, unit "Mcy" consists mainly of gypsum.

The Cuayuca Fm. was dated as late Miocene to early Pliocene by Fries (1966). Nevertheless, recent palynostratigraphic studies had allowed to give a new chronostratigraphic assignment: late Eocene – Early Oligocene (Ramírez y Martínez, 2001). According with palynological and stratigraphic characteristics it could belong to Balsas Group, sensu Fries (1960). The Balsas Group is characterized by a series of basins with lacustrine, alluvial and sedimentary volcanic deposits associated with two tectonic events: Chortis block displacement and Xolapa Complex exhumation. The goal of this study is to give a palynological synthesis of Cuayuca Fm. in order to compare it with Tertiary Flora from Tepexi belonging to Balsas Group.

A total of seven stratigraphic sections from 25 to 60 meters in thickness were studied. Three of them were prospected at stratotypes in Cuayuca (18º32’ N and 98º), other two outcrops were near Cuayuca and two more sections were sampled at Izucar de Matamoros (18º36’ N and 98º29’).

Considering all sections, only Cuayuca and Izucar outcrops had the most diversity. In general, the abundant plants were Pinus, Picea, Momipites group, Chenopodiaceae-Amaranthaceae, Gramineae and Ephedra. Meanwhile palynoflora with low frequencies were Acacia, Alchornea, Anacardiaceae, Arecipites, Asteraceae, Bombacacidites, Bursera, Corsinipollenites, Lycopodium, Moraceae, Tiliaceae and Ulmaceae.

Besides, palynomorphs of chronostratigraphic importance as Aglaoredia, Armeria, Juglans, Cicatricosisporites, Echinatisporis, Emmapollis, Eucommia, Liliacidites and Verrucingulatisporites were present. In general, palynomorphs represent different types of vegetation through an altitudinal gradient.

Paleopalynological results were correlated with flora of Balsas Group at Tepexi Region (Martínez y Ramírez, 1999). Although both represent Paleogene flora, the analysis grouped separately. We suggest that they could be two different Tertiary basing where stratigraphic sections reflect different types of subenvironments. Finally, presence of phycomes and sapropelic material suggest a lacustrine to blackish water environment.

PALYNOLOGY AS A TOOL FOR RESERVOIR CHARACTERISATION AND VEGETATION HISTORY IN THE DEEP WATER AMAZON FAN, BRAZIL

K. RICHARDS

KrA Stratigraphic, 43 Ty Mawr Road, Deganwy, Conwy, LL31 9UD, UK

BP Exploration, UTG, Sunbury on Thames, Middlesex, TW16 7LN, UK

The Amazon Fan is approximately 10 million years old and was formed after Andean uplift gave rise to the Amazon river system. This study presents a summary of biostratigraphic results from Pleistocene and Late Pliocene sediments from several wells drilled in deep water on the fan. Foraminifera indicate that the studied sections were deposited in deep shelfal or bathyal settings. Age dating is based mainly on nannofossils with peak abundances, in most cases, equating with maximum flooding surfaces or lowstand condensed sections. Sequence boundaries are suggested at 1.4 Ma (Early Pleistocene), 1.9 Ma, 2.4 Ma, 2.6 Ma and 3.0 Ma (Late Pliocene).

The palynological records include highly diverse pollen and spore assemblages reflecting the wide range of vegetation types in the Amazon catchment. Marine dinocysts are locally common but may be transported from the marine shelf into deeper water. Mangrove pollen occur only in low to moderate numbers, probably due to continually strong freshwater influence. Abundance peaks of freshwater algae indicate times of maximum freshwater discharge. Reworked elements are present in most samples but are of limited stratigraphic value. Fern spores, grass pollen and cold tolerant pollen types such as Podocarpus and Alnipollenites verus are frequent in some intervals and indicate that a large proportion of the palynoflora originates from Andean and sub-Andean localities. This type of river discharge is referred to as "whitewater", reflecting a high sediment load, mostly of fine clastics. Deposition during periods dominated by "whitewater" discharge is predicted to be mainly mud-prone and is therefore unlikely to result in deposition of extensive reservoir sands within the Amazon Fan.

Several intervals within the Early Pleistocene and Late Pliocene contain increased quantities of charred Gramineae (grass) cuticle which probably originates mainly from "cerrado"(wooded grassland) or semi-deciduous woodland. These are mostly dry, fire-prone localities found mainly to the south and east of the Amazon catchment at the present time, where Paleozoic rocks of the Brazilian Shield are often exposed. Peak abundances of charred cuticle in the sedimentary record are thought to result from periods of very dry climate, after which seasonal floods rejuvenated dry or ephemeral rivers: these are "clearwater " rivers which carry mostly coarser clastics, including quartz-rich sands eroded from the Brazilian Shield. Deposition during periods of significant "clearwater" discharge is likely to be sand-prone and may, therefore, produce potential reservoir intervals within the Amazon Fan. Palynology is shown to be useful in determining types of river discharge in the palaeo-Amazon which can assist with sequence modelling and reservoir prediction.

TECHNIQUES IN PALYNOLOGY FOR RESERVOIR BAFFLE CORRELATION AND PREDICTION OF LATERAL BAFFLE EXTENT

M.H. STEPHENSON

British Geological Survey, Keyworth, Nottingham, NG12 5GG, UK

Petroleum Development Oman,PO Box 81, Muscat 113, Sultanate of Oman

Multivariate analysis of complex palynological data from the Early Permian oil- bearing Gharif and Al Khlata Formations of Oman has allowed the identification of several terrestrial and marine plant palaeoecologies in a periglacial environment. These include upland and lowland plant palaeoecologies as well as areally restricted floodplain freshwater algal ecologies. When these ecologies are uniquely associated with mudstone baffle horizons within hydrocarbon reservoirs, correlation at a resolution well beyond conventional palynostratigraphy is possible. In addition, knowledge of ecologies closely associated with thin mudstone baffles allows prediction of their lateral persistence and variability within a reservoir; this allows reservoir engineers to model the extent of vertical hydrocarbon fluid flow within producing sequences. In areas where mudstone baffles are persistent or field-wide, less oil yield can be expected.

TEMPORAL AND SPATIAL PATTERNS OF ENVIRONMENTAL CHANGES IN THE LATE SILURIAN OF GOTLAND: A PALYNOLOGICAL PERSPECTIVE

L. STRICANNE, A. MUNNECKE, J. PROSS

Institute of Geosciences , Sigwartstr. 10, D-72076 Tübingen, Germany

Sciences de la Terre, UPRESA 8014 CNRS, F-59655 Villeneuve d'Ascq, France

The Silurian succession of Gotland shows a distinct cyclicity in facies development and stable C and O isotopes. Most of the Silurian of Gotland is characterised by the deposition of argillaceous limestones and marls with low d¹³ C_carb and d¹⁸O_carb values. In the early and late Wenlock as well as in the middle and late Ludlow, these sediments are interrupted by extended carbonate platforms and reefs characterised by high d¹³ C and d¹⁸O values. To date, three of these positive isotope excursions are known from contemporaneous deposits on different palaeo-continents. This suggests global steering mechanisms, probably reflecting changes between humid (H) and arid (A) climate conditions. Concomitant with these changes, major extinction events occurred in different groups of organisms, especially at the transition from H to A periods. In southern Gotland, one of these H/A transitions is represented by the Hemse-Eke boundary (late Ludlovian). To better understand the environmental changes during that time, we have initiated a palynological study focussing mainly on acritarchs and prasinophytes, but also on chitinozoans, spores, and scolecodonts. To date, 60 samples have been investigated.

28 samples are from the Hemse Beds and represent a transect from a lagoonal setting with desiccation cracks to the distal shelf. Within this transect, obvious patterns of opposite trends in lateral distribution of acritarchs and prasinophytes are well defined. Acritarchs show an increasing proportion towards the distal shelf, while the prasinophytes proportion is decreasing. Within the acanthomorphic acritarchs, some genera occur only in proximal facies (i.e. Dilatisphaera spp., Micrhystridium spp.), while others are only present more distally (i.e. Percultisphaera spp.). Within the Micrhystridium plexus, morphotypes with shorter processes are mainly present in proximal environments, while those with longer and ramified processes occur more distally.

The results from this transect are compared with two vertical sections across the Hemse-Eke boundary in proximal and distal environments (8 and 24 samples, respectively). Both sections show an upward decrease of acritarchs and an increase of prasinophytes together with a strong reduction of absolute palynomorph abundances. Within the acanthomorphic acritarchs, some genera are more abundant at the top of the section (i.e. Micrhystridium), while others (i.e. Percultisphaera) disappear within the interval. The proportion of Micrhystridium morphotypes with shorter processes increases through time, while the proportion of morphotypes with longer and ramified processes decreases. These observations indicate that the Hemse-Eke transition shows a trend to more proximal conditions, thus suggesting a regression during that time interval.

NEW DEVELOPMENTS IN QUANTITATIVE HIGH RESOLUTION BIOSTRATIGRAPHIC CORRELATION

BG Group, 100 Thames Valley Park Drive, Reading, RG6 1PT , UK

Technical Alliance for Computational Stratigraphy, Energy & Geoscience Institute, University of Utah, 423 Wakara Way, Suite 300, Salt Lake City, Utah 84108, USA.

Biostratigraphical resolution has increased markedly over the past few decades. The use of origination and extinction datums has been supplemented, particularly at the reservoir scale, by more local 'bioevents and biozones' in the form of successions of unique abundance fluctuations of individual taxa and distinct faunal/floral assemblages. Such high-resolution work is currently subjectively undertaken and applied.

Sequence slotting provides an objective method for matching an ordered sequence of measurements against a given reference sequence. The method makes no a priori assumptions about the successions to be correlated. It uses pair-wise differences between samples (a similarity matrix) and the known order of observations in each sequence. In reality this is 'correlation' by determination of the rank order of sample depths between two successions, rather than sample-to-sample correlation. Lateral tracing also uses a similarity matrix through which a sample-to-sample correlation path is drawn by tracing adjacent points of high similarity.

DOS freeware for sequence slotting is available at class=MsoHyperlink> style='color:blue'>http://www.kv.geo.uu.se/inqua (e.g. SlotDeep and PCSLOT). No software exists for lateral tracing. In addition, the software package BioSlot was recently developed by the Technical Alliance for Computational Stratigraphy (TACS) as part of an industrial consortium (sponsored by BG Group, BP, Chevron, Conoco, Shell & Unocal) to address reservoir-scale correlation using quantitative biostratigraphical data. Like the packages above, BioSlot incorporates a slotting algorithm based on finding the optimal path through a similarity matrix. BioSlot also features: (1) the ability to import primary horizons (e.g. flooding surfaces) to constrain the sequence slotting solution; (2) an integrated taxon abundance plot feature to aid in identification of field-scale correlation bioevents; and (3) a variety of options for data filtering, data transformations and similarity metrics.

Sequence slotting has been applied in the correlation of quaternary palynological data (comprising quantitative counts of pollen & spores, usually of climatic significance e.g. Quercus, Alnus & Ilex). It has proven particularly useful in application to lake cores. This poster demonstrates the reservoir scale application of BioSlot using BG proprietary data; North Sea Cretaceous palynological data and Mediterranean Plio-Pleistocene nannofloral data. The inclusion of additional a priori information such as palaeobathymetric curves derived from the benthonic foraminifera and wireline log data, is shown to aid the definition of the 'Line of Correlation' through the BioSlot similarity matrix and to increase confidence in the correlation. Correlation resolution when analysing the Plio-Pleistocene nannofloral data was increased by focussing on generic groupings known to be evolving rapidly at the time. The correlation resolution provided by BioSlot is above that provided by conventional magnetobiochronological dating of the succession.

DEVELOPMENT OF AN AUTOMATED MICROSCOPY SYSTEM FOR THE IDENTIFICATION AND QUANTIFICATION OF SEDIMENTARY ORGANIC MATTER AND DINOFLAGELLATE CYSTS IN PALYNOLOGICAL PREPARATIONS

A. WELLER

Environmental Research Unit, School of Applied Sciences, University of Glamorgan, Pontypridd, CF37 1DL, UK

A system to advance the identification and quantification of sedimentary Organic Matter (OM) and dinoflagellate cysts is being created through the integration of isolated disciplines: palynology; image processing; and Artificial Neural Networks (ANNs). This system cannot replace human experts, but will: enhance their work; decrease the cost and time of analysis; increase the sampling resolution; allow complete objectivity in identification; facilitate continuous operation; and have no subjective bias.

Image acquisition and pattern recognition is achieved through image processing operators using the HALCON (www.mvtec.com/halcon/) software suite and the analytical component is to be comprised of several dedicated ANNs. Images of the OM are acquired for retrieval and subsequent viewing on a personal computer via a digital camera mounted on a transmitted light microscope with a computer-controlled stage. These are then: A] pre-processed (to clean-up the image, for example, to reduce the effects of non-uniform illumination); B] segmented (where the foreground/particles within each image are separated from the background); C] enhanced (to promote the features relevant for identification, for example, to change the brightness/contrast); and D] extracted and measured (for example, location of features, morphological properties, object boundary shape properties, frequency domain properties and texture) through HALCON. Resultant measurements based on the features extracted will be passed to several ANNs for visual classification. These are powerful pattern-recognition and data analysis tools; they perform visual classification tasks very effectively with their capacity to classify a wide range of features and to tolerate small differences in the object identified. Other advantages include rapidity of training, efficiency of operation and an ability to produce reasonable decision regions.

Nomenclature for palynofacies has been qualitatively and subjectively described in many papers. An adapted classification is utilised with this system for this quantitative and objective approach. The advantages to the palynologist for this system include the automated scanning of the microscope slide with classification of palynofacies to produce a count and a coordinate log of the assemblage. The images of each palynomorph will be extracted and stored for identification, with the sorting of dinoflagellate cysts into morphological groups. This will allow the later recall and simultaneous display of the dinoflagellate cyst images within these groups, to aid the identification procedures for the palynologist.

MARINE PALYNOLOGY ACROSS THE CRETACEOUS-TERTIARY BOUNDARY IN NEW ZEALAND

P.S. WILLUMSEN

Svinget 3, 1 th., 2300 Copenhagen S, Denmark

A palynological investigation of eight Cretaceous-Tertiary boundary sections located on the mainland in New Zealand resulted in the development of a new high resolution dinoflagellate cyst zonation for the latest Maastrichtian and early Paleocene. Seven new subzones are proposed and they are defined by a combination of new and already described taxa. The oldest subzone proposed, the Carpatella sp. 1 subzone, corresponds to the latest Maastrichtian (top of the Manumiella druggii zone of Wilson, 1984, 1988; Helby et al., 1987). The six early Paleocene subzones, Senoniasphaera inornata, Carpatella cornuta, Cassidium fragile, Cerodinium striatum, Tectatodinium meandriforme and Cassidium filosum span approx. 3 Ma of the early Paleocene (Trithyrodinium evittii zone and lower part of the Palaeocystodinium golzowense zone of Wilson, 1988). The northern Hemisphere index dinoflagellate cyst for the earliest Paleocene Damassadinium californicum was not observed whereas other short ranging earliest Paleocene markers such as S. inornata and C. cornuta were recorded. A new species in the genus Palynodinium was also observed and this is the first record of this stratigraphically important late Cretaceous genus from the mid latitudes, southern Hemisphere.

An examination of the palynofacies and dinoflagellate cyst composition was also undertaken in three out of the eight sections studied. A gradual extinction of most of the latest Maastrichtian species take place approx. 0.5 Ma after the KTB and is therefore not related directly to this extinction event. A distinct acme of Diconodinium martianum was observed in the latest Maastrichtian and is interpreted as a short climatic shift from relatively colder to warmer surface water conditions immediately below the KTB. In the early Paleocene the two protoperidioid cysts T. evittii and Palaeoperidinium pyrophorum occurs as distinct acmes (>40% of the relative amount of cysts). The two acmes of T. evittii are interpreted to represent periods with warmer surface water conditions separated by a period with relatively colder and perhaps also more saline water masses (dominance of P. pyrophorum).

These early Paleocene "blooms" of specific dinoflagellate cysts was probably only partly controlled by the upwelling regime that influenced the eastern New Zealand margin during the latest Cretaceous to early Tertiary (Hollis et al., 1995). A similar pattern of acme intervals of T. evittii in the earliest Paleocene has also been observed from a high latitude site in the northern Hemisphere, West Greenland, by Nøhr-Hansen and Dam (1997; 1999).

TIME IN STRATIGRAPHY – INTEGRATING THE GRAPHIC CORRELATION METHOD WITH SEQUENCE STRATIGRAPHIC CONCEPTS

R. WOOLLAM

InteBios, 37 Beaufort Avenue, Kenton, Middlesex HA3 8PF, UK

The graphic correlation method originated in A.B Shaw’s groundbreaking book - Time In Stratigraphy - published in 1964.  It provides a simple but powerful tool for analysing any event-based geological information, although its main use to date has been in biostratigraphic applications. While approaches have varied over the years, graphic correlation essentially involves displaying data on bivariate, xy cross-plots, where age is usually plotted on the x-axis and depth on the y-axis.

When applied to biostratigraphic data, a graph is constructed using bioevents observed in a section cross-plotted against their known age in a reference scheme scaled in linear time. Data from many disciplines can be combined on a single graph without separate interpretations being produced for each fossil group - a significant advantage over biozonation. The graphed bioevent data usually show a linear trend indicating increasing age with increasing depth. A degree of scatter will be apparent resulting from complexities in the fossil record, compounded by sampling effects. The bioevent distribution is used to interpret the position of the Line Of Correlation (LOC). For any given section, there is only one true LOC and the challenge is to find it.

The LOC represents the correlation between depth and time for the section and allows transformations between the axes using interpolation. Much of the literature on graphic correlation concerns its use in building composite standard ranges for fossil species using depth-to-age interpolations. The converse transformation, age-to-depth, has received much less attention, despite the fact that it allows quantitative isochron correlations to be established between sections. Where correlation between sections is described, it is often limited to direct comparison of pairs of sections derived from depth-depth graphs, which tend to diminish critical sequence information. More recently, studies have started to appear on the use of graphic correlation in integrated sequence stratigraphic analysis. Here, the focus is on the varying character of the LOC.

Employing a widely known and accepted sequence model, it is possible to derive a series of idealised LOCs to illustrate the theoretical basis for sequence stratigraphic interpretations using graphic correlation. In each case, the LOC takes the form of a series of sloping ramps and flat terraces. Ramps represent intervals of sediment accumulation. Terraces locate significant stratigraphic breaks (hiatal intervals), whether resulting from erosion, non-deposition or condensing. While the exact interpretation of terraces clearly depends on geological context, terraces always identify the key bounding surfaces within the sequence stratigraphic framework.