Abstracts of the Proceedings of the Thirty-Fourth Annual Meeting of the American Association of Stratigraphic Palynologists
London, England — September 11-13, 2002

PALYNOLOGICAL IDENTIFICATION OF SYSTEMS TRACTS IN JURASSIC PARALIC DEPOSITS IN THE NORTH SEA BASIN

O.A. ABBINK

TNO-NITG, P.O. Box 80015, 3508 TA Utrecht, NL

Paralic depositional sequences in the Jurassic of the North Sea form an important economic objective. In these sequences, palynomorphs are the most abundant (micro) fossil group and palynology is increasingly challenged to identify systems tracts and parasequences.

Based on the general ecologies of aquatic palynomorphs and on a recently developed Sporomorph EcoGroup model it can be demonstrated that (1) the interplay of the distribution patterns of brackish-marine, freshwater and terrestrial palynomorphs, and (2) distribution patterns of even solely terrestrial palynomorphs (grouped in six Sporomorph EcoGroups (SEGs), viz.  Upland, Lowland, River, Pioneer, Coastal, and Tidally-influenced SEG), can be used for the recognition of sea-level fluctuations in paralic settings.

The sea-level changes recognized based on the SEG model allow the identification of discrete palynological sea-level induced units (Sea-level Induced Palynomorph Succession; SIPS). Within the SIPS (see Figure, four phases can be distinguished: (1) a "wet" Lowland SEG phase, (2) a phase with maximum abundance of Upland, Coastal and/or Tidally-influenced SEGs and a high marine/terrestrial ratio, (3) a Coastal SEG phase, and (4) a "dry" Lowland SEG phase. Based on the correlation of water-balance and drainage conditions with sea-level, the four phases are considered to correlate to the (1) late LST and TST, (2) MFS, (3) early HST, and (4) late HST, respectively. The boundary of between SIPSs reflects the abrupt shift from a regressional to a transgressional regime and is considered to approximately correlate to the SB in a paralic setting.

School of Earth and Geographical Sciences, University of Western Australia, Crawley WA 6009, Australia

Energy and Geoscience Institute, The University of Utah, 423 Wakara Way, Suite 300, Salt Lake City UT 84112, USA

Geological Survey of Western Australia, 100 Plain St, East Perth, WA 6004, Australia

School of Earth and Geographical Sciences, University of Western Australia, Crawley WA 6009, Australia

Initial findings of a major project on the Australian Cretaceous are presented. The project integrates palynostratigraphy, foraminiferal and nannofossil biostratigraphy, petrophysical logs and sedimentology to document and correlate events that can be recognized on the Southern Carnarvon Platform of Western Australia

. This region is the classic area for study of the Australian Cretaceous, and part of every stage from the Barremian to Maastrichtian is represented. It is a tectonically stable area lying south of the North West Shelf, and during the Cretaceous was a stable, low-gradient continental shelf that formed during mid-Valanginian continental breakup.

A programme of continuous coring and sampling, at one metre or less intervals, has provided material from all parts of the subsurface succession. All available surface sections have been sampled. Shallow burial has resulted in excellent microfossil preservation, in contrast to that in the Cretaceous of the North West Shelf (more deeply buried) and the

Papuan Basin (tectonically deformed).

The Cretaceous on the platform represents a succession of late transgressive and early highstand depositional phases. Initial results show four progressively deepening siliciclastic depositional cycles, Barremian to early Aptian (with inner neritic maximum flooding), late Aptian (mid neritic), Albian (mid to outer neritic) and early to mid Cenomanian (shallow outer neritic). Similar Aptian to Albian sequences are recognized in the vast interior basins of Australia. The Turonian to Maastrichtian interval is a carbonate succession with five main depositional cycles representing the early to mid Turonian, late Coniacian to Santonian, late Campanian and late Maastrichtian, with maximum outermost neritic water depths during the Turonian and the Santonian to early Campanian. Hiatuses separate the major sequences but many minor hiatuses are present. The identification of tightly controlled species datum levels within this succession will enable a standard Cretaceous chronostratigraphy and chronometry for northern and western Australia. Despite several intervals of non-deposition, long continuous sections provide accurate range data for critical index species, and enable comparison of ranges between many cosmopolitan dinocysts, planktonic and benthic foraminifera, and calcareous nannofossils.

ERIC O. CALLEN AND THE EARLY YEARS OF COPROLITE ANALYSIS (1900-1970)

V.M. BRYANT, Jr.

Department of Anthropology (TAMU-4252), Texas A&M University, College Station, Texas 77843-4352, USA

Office of Cultural Affairs (Rm 320), 228 E. Palace Ave., Santa Fe, NM 87501, USA

The detailed analysis of human coprolites, as a recognized field of science, is barely 40 years old.  Dr. Eric O. Callen, the founder and developer of the discipline, has been dead for more than 30 years yet the techniques and ideas he developed and perfected continue to guide the discipline today; a discipline that has refined analyses in areas than he would ever have dreamed possible.  Callen ushered in the modern age of human coprolite analysis during the late 1950s and early 1960s.  He worked alone and with missionary zeal to convince archaeologists, botanists, zooarchaeologists, and anyone else who would listen of the importance of prehistoric human fecal research. From the beginning many fellow scientists considered his research to be unimportant and frivolous yet Callen never wavered from his commitment until his untimely death in Peru in 1970.

Eric Callen was an unlikely person to become the "father" of coprolite analysis.  He had no anthropology or archaeology background.  After receiving a doctorate in botany from the University of Edinburgh in Scotland he spent his entire career as a professor of plant pathology at McGill University in Canada. His first exposure to the study of coprolites came by accident when an archaeologist gave him some prehistoric human feces that had been found during the excavation of an early agricultural site in the coastal region of Peru.  Callen’s initial interest in the fecal remains consisted only of a search for fungal spores of potential plant pathogens that might have infected prehistoric Peruvian maize, and in turn been harvested and eaten with maize by humans.  That initial study led Callen into a new dimension of research, which was to become the basis for all future coprolite studies.  Callen’s initial diet reconstructions were based on a wide variety of plant and animal macro evidence that he discovered during his first analysis. Although not a palynologists, he was quick to realize the potential value of pollen studies and worked with others to examine the pollen from his fecal studies.  His new coprolite research interest was far removed from the academic courses he taught, the plant pathology research he conducted, and it earned him little praise or respect from his colleagues most of whom believed he was wasting valuable research time.

During the short period of his remaining life he developed the standards now used for coprolite processing, identification, and analyses. However, for years no other scientist followed in Callen’s path. Callen never taught a course on the subject, never received an award or praise for his pioneering efforts, and had only one graduate student who was ever interested in fecal research. During his brief decade of coprolite research Callen’s only research space was a tiny 6 x 8 foot room and he was frequently the victim of jokes and reticule by his colleagues.

Today, Callen would be gladdened to learn that after his death others built upon his initial research efforts and extended fecal studies to include the analysis of plant macrofossils, pollen, phytoliths, amino acids, trace elements, pollen concentration values, gas chromatographic data, faunal and insect studies, and most recently the extraction and identification of DNA from human feces using PCR techniques.

THE RAVENSCAR GROUP: A GEOLOGICAL ANALOGUE FOR THE MIDDLE JURASSIC RESERVOIRS OF THE NORTH SEA AND MID NORWAY

N. BUTLER

Robertson Research Int. Ltd., Llanrhos, Llandudno Ll30 1SA, UK

Norsk Hydro AS, Research Centre, N-5020, Bergen

Norsk Hydro AS, Luanda, Angola

Robertson Research Int. Ltd., Llanrhos, Llandudno Ll30 1SA, UK

Despite their maturity, Middle Jurassic sandstones of the North Sea and Mid Norway still represent some of the most prolific hydrocarbon reservoirs in Northwest Europe.  Of these, the Brent and Fangst Groups are particularly important and despite the vast number of penetrative wells, the published chronostratigraphic schemes are poorly calibrated with well-dated, onshore sections.

The current scheme features improvements in stratigraphic resolution, which are largely the result of an integrated biostratigraphic and sedimentological study of the Middle Jurassic Ravenscar Group, Cleveland Basin, England.  A field excursion involving Robertson and Norsk Hydro geologists was undertaken to investigate relevant sections on the Yorkshire coast.  A detailed composite log was produced for the Dogger, Saltwick, Eller Beck, Cloughton and Scarborough Formations where sedimentary facies are comparable to those seen in Brent and Fangst Group cores.  Additionally, lateral facies relationships and typical facies sequences were documented.  These localities were simultaneously sampled for high-resolution biostratigraphy and in excess 100 samples were analysed for palynology and micropalaeontology.  The resultant dataset has been integrated with the sedimentological facies to place the quantitative biostratigraphic data within a detailed depositional framework.  As a result of this integration the following observations have been made:

1.  The shelfal marine, condensed Dogger Formation is of ‘earliest’ Aalenian age and correlative with Broom and Ile Formations. 

2.  The Aalenian Saltwick Formation (non-marine/brackish coastal plain/deltaic sediments) and Eller Beck Formation (marine incursion) correlate with Rannoch-Etive-Ness and the Not-‘lower’ Garn genetic packages. 

3.  The variably non-marine to shelfal sediments of the Cloughton Formation is either unrepresented or may be only partly represented in the Brent Province and Mid Norway due to a regional unconformity which truncates early Bajocian sediments.

 4. The Scarborough Formation is a retrogradational package, which was deposited in a shelfal environment and is of ‘latest’ early to ‘earliest’ late Bajocian age.  The formation is correlative with the older part of the Tarbert-Heather and the ‘upper’ Garn-Melke genetic packages.

  Studying robustly dated outcrop analogues which lack major stratigraphic breaks like the Ravenscar Group can provide data which may be used to improve reservoir modelling on both regional and field-wide scales and consequently contribute to hydrocarbon exploration and production strategies.

PALEOGENE PALYNOSTRATIGRAPHY OF THE PALEOLAKE (TEPEXI COATZINGO) AT THE PUEBLA STATE, MEXICO

C. CARRANZA-SIERRA, E. MARTÍNEZ-HERNÁNDEZ

Instituto de Geología, Dpto. Paleontología. Lab. Palinología, Ciudad Universitaria, Coyoacán, 04510 D. F., México

The Balsas group was proposed by Fries in 1960, formed by variety of lithological units such as conglomerates, siltstones, tuffs, gysums and lacustrine limestones. The Balsas group filled the hydrological basin Mezcala-Balsas River in southern Mexico.

Previously there are reports of the easterly part of this paleolake. In accordingly with the results obtained by Martinez & Ramirez 1999, it was propose to launched a large survey toward the west of the basin was a large lake extending several kilometers to the west. The new localities studied proof the hypothesis that the Tepexi- Coatzingo was a large lake extending several kilometers to the west.

The new localities studies are listed as:

"Loc. Pie de Vaca" Tepexi de Rodriguez. That is a lithological sequence of 53 meters, formed by siltstones and lacustrine limestones. Its age was erroneously established as Pliocene Pleistocene base on footprints and a flamingo cast. In this locality a new closely spaced sampling was undertaking near the flamingo. In these limestones several fungospores are presence as Pluricellaesporites van der Hammen 1954, cf. P. beaufortensis Parson & Norris 1999 reported for Paleocene of Texas USA; Hypoxilonites Elsik 1990a; cf. Brachyporisporites atratus Kalgutkar 1993. The pollen grains are few. This assemblage confirms the Paleogene age of this locality.

Loc. "El Tronco" Near Cuayuca

The assemblage yields pollen Liliacidites, aff. Loeselia mexicana, Alnuspollenites, Momipites, fresh water algae; Cymatiosphaera, Leiospheridia, Ovoidites grandis, Zygnemataceae, Mycrocystis. Fungi spores: Diplodites, Papulusporonites.

Loc "Techcalli Blanco" Mimiapan

This section of 50 meters constituted by siltstones and sandstones is characterized of Pinuspollenites, Alnuspollenites, aff. Convolvulaceae, aff. Operculina codonatha, Chenopodipollis, Quercoidites, aff. Gunnera, Myrtaceae, Potamogetonaceae, fresh water algae; Cymatiosphaera. Fungi spores: Diplodites, Pluricellaesporites, Papulusporonites, Fusiformisporites, Hypoxylonites, Dicellaesporites, Dictiosporites, Multicellites, inapertisporites.

Palaeoenvironmentally, these localities represent an ancient lake where abundant fresh water sapropel with fragments of fresh water algae, fungal spores, were deposited. These facies can be correlated with other units previously studied in the Coatzingo-Tepexi basin. These finding confirm the existence of the great Coatzingo-Tepexi paleolake, probably, situated near the sea level.

STRATIGRAPHIC CALIBRATION OF LATE CRETACEOUS SEQUENCES, OFFSHORE MID NORWAY AREA.

M. A. CHARNOCK

Norsk Hydro Research Centre, N-5020 Bergen, Norway

SC Independent Geological Consultant, Chagford Devon, United Kingdom

The deeper water areas of the Vøring Basin , offshore Mid- Norway area, represent one of the last major frontier areas for hydrocarbon exploration in the Norwegian Sector. To date, single wells have been drilled on some of the larger structures e.g. Helland-Hansen Arch, Gjallar Ridge and Vema Dome targeting thick sequences of Upper Cretaceous, deep marine clastics. With the exceptions of the giant Ormen Lange gas field on the Møre margin and the Nyk High (gas discovery), hydrocarbon success rate has been low and disappointing but this is considered to be mainly related to understanding the hydrocarbon source and migration history rather than the lack of significant reservoirs. The challenge has been to integrate the biostratigraphy, well logs and seismic information to produce a regionally applicable, sequence stratigraphic framework to link these structures and improve our understanding of the geological evolution of the area.

This study presents the sequence stratigraphy and biostratigraphic characterisation of the Upper Cretaceous interval and the interpretation is based on an extensive biostratigraphic review of wells from Quadrants 6305 to 6707. The surfaces have been defined, in practical terms, by a series of 'key' microfossil events based on a combination of palynology (marine microplankton) and micropalaeontology (planktonic and benthonic foraminifera, radiolaria and diatoms) to correlate surfaces designated as representing either sequence boundaries (SB), transgressive surfaces (TS) or surfaces of maximum marine transgression (MTS) for integration with wireline logs and seismic stratigraphy. A series of type sections are designated using or relating these, wherever possible to the wells designated by Dalland et al. (1988) in their development of a lithostratigraphic scheme for the better understood Halten Terrace area of the eastern basin margin and the biostratigraphic zonation is calibrated to the standard chronostratigraphic framework established for European Basins by Hardenbol et al. (1998). It is possible to relate most of the microfossils events to stratigraphies established elsewhere, particularly the Shetland facies developed in the Viking Graben of the North Sea basin, suggesting a provincial similarity that is useful for large scale correlation.

The main periods of deep - water sandstone development are within sequences K50 (early - late Turonian): 'Upper Lange Sandstones', K60 (late Turonian - Santonian): Lysing Formation ('latest Turonian'- Coniacian) and 'Kvitnos Sandstones' (Santonian); K70 ('latest' Santonian- middle Campanian): 'Nise Sandstones' and K90 (late Campanian - late Maastrichtian): 'Springar Sandstones'. Long distance stratigraphic correlations, depositional environments and sediment sourcing are presented and discussed.

Intra - Late Cretaceous stratigraphic breaks are relatively rare, and difficult to identify from the wireline log responses of the predominantly claystone intervals in this deeper water area with the exception of the Cretaceous/Tertiary rifting event which shows variable but sometimes significant truncation of the underlying Shetland Group.

Biostratigraphy has therefore had an important role in the recognition, interpretation and correct regional correlation of Late Cretaceous sequences in the offshore Mid - Norway area.

BIOSTRATIGRAPHIC IMPACT ON THE RESERVOIR ARCHITECTURE AND BASIN MODELLING OF THE GIANT ORMEN LANGE GAS FIELD SPANNING THE CRETACEOUS / TERTIARY BOUNDARY, OFFSHORE MID-NORWAY

M.A. CHARNOCK

Norsk Hydro, Research Centre, N-5020 Bergen, Norway

Norsk Hydro Exploration and Production, N-0246 Oslo, Norway

L.I. COSTA, R.J. DAVEY, M. WELDON

 Robertson Research International Ltd, Llandudno, North Wales, LL30 1SA, U.K.

The Ormen Lange Field in the Møre Basin, offshore Mid-Norway was discovered in 1997 with the drilling of the 6305/5-1 well and is the first commercial deep-water discovery in the Mid - Norway area and the second largest gas discovery in the Norwegian Sector. The reservoir system comprises Maastrichtian to Danian deep marine, sand-rich turbidites spanning the K/T boundary (figure 1). The reservoir has been cored in four wells, and significantly, both from an industrial as well as academic perspective, three have a continuously cored K/T boundary record and represent the most complete boundary sections in present day high latitudes.

High-resolution biostratigraphy using both quantitative palynology and micropalaeontology has had a significant impact on our understanding of the reservoir system. This has been primarily focused on detailed intra-reservoir correlations and establishing a stratigraphic framework, often below seismic resolution, of the five reservoir units. The correlations show there is considerable variation in the depositional style and geometry of these different units. In general, the oldest, i.e. Maastrichtian Jorsalfare Sandstone Unit is a more uniformly correlatable sequence than the highly variable, amalgamated channel-fill sequences of the younger, Lower Paleocene main reservoir Egga Sandstone Unit where a series of dinoflagellate cyst events suggests the system attempted to compensate and adjust to variations in topography through time. In the middle of the sequence are the Våle Tight and Våle Heterolithic Units. The latter spans the K/T boundary (defined by the extinctions of P. grallator and Heterohelix/Globigerinelloides spp.) which coincides with the onset of black mudstones. The Våle Heterolithic Unit is a complex unit with deformed sandstones partly interpreted as injection features and the overlying Våle Tight Unit is a thin unit of black mudstones and is important to define biostratigraphically since it may act as a permeability barrier during production. Dating of the whole reservoir sequence by calibrating selective bio. - events to the Hardenbol et al. (1998) timescale indicates the system was deposited in <8Ma. The Early / Late Paleocene boundary lies within overlying hemipelagic mudstones of the Våle Formation, with planktonic foraminifera, and coincides with a transgressive event which terminated sand deposition in the area. Study of the overlying Cenozoic sediments and the recognition of a mid-Miocene stratigraphic break has provided information for basin modelling.

Biostratigraphy has secondarily attempted to solve problems associated with reservoir characterisation. Analysis of the reworking has revealed palynomorphs with a range of ages (Permo-Trias. to Maastrichtian) and has provided useful information on sediment sources and the uplift history. The reworking is generally in an 'inverted stratigraphy' and suggests the progressive erosion of the source area with sediment derivation from a single point source. Micropalaeontology has attempted to identify turbiditic and hemipelagic mudstones. Widespread and continuous intra-reservoir mudstones act as permeability barriers. The frequency of planktonic foraminifera and radiolaria characterise hemipelagic intervals and to a lesser extent, diverse agglutinated foraminifera suites (sensu Winkler, 1985). The majority of the mudstones, however, within the main Egga Unit have none of these indicators and may represent discontinuous turbiditic mudstones and erosional remnants between channels.

DINOCYSTS FROM THE FINLAY LIMESTONE (ALBIAN), CERRO DE CRISTO REY, NEW MEXICO, USA

W.C. CORNELL

Dept. of Geol. Sci., University of Texas at El Paso, El Paso, Tx 79968, USA

Outcrop samples of the Finlay Limestone, exposed on the west bank of the Rio Grande, in southernmost Doña Ana County, New Mexico, have yielded numerous dinoflagellate cysts, large numbers of bisaccate pollen, and rare trilete spores.  Marls, nodular limestone, and massive limestone beds (to 4 m thick) are present in the 40 meter-thick section.

Cysts assigned to four, possibly five, genera in the Family Deflandreaceae are the most abundant, contributing 25 – 75% of the cysts in the samples.  Spiniferites species occur throughout the section, averaging approximately 10% of the cysts in each sample. Odontochitina species also occur in all samples but total fewer than 10 % of the cysts in each one.  Overall abundance and taxonomic diversity is influenced by facies – the massive limestones yield low-diversity, Deflandreacean-dominated assemblages. Marly sequences, on the other hand, yield both the largest numbers of cysts and assemblages of greatest diversity.  Nodular sequences fall in between in both diversity and cyst abundance.

Although the outcrops lie less than 600 m (map) from an Eocene andesite pluton, the cysts and pollen show no signs of thermal alteration, having TAI values (Pearson scale) of 1 or less.

THROUGH THE MICROSCOPE: A LOOK AT EARLY AND LATE CHRISTIAN DIET IN NUBIA

L.S. CUMMINGS

Paleo Research Institute, 2675 Youngfield St., Golden, Colorado, 80401 USA

Coprolites associated with individuals excavated from two cemeteries at Kulubnarti in Sudanese Nubia provided a rich record of pollen, phytoliths, macrofloral remains, and bones, reflecting diet.  These cemeteries represent ancient agricultural cummunities of the early Christian period (AD 550-750) and the later Christian period, which terminated in the mid-15th century.  Study of these coprolites is unique in that each coprolite is associated with a body, providing age and sex information.  Further population comparisons may be made between observations of nutritional completeness, based on the coprolite evidence, and evidence of nutritional deficiencies noted by separate hair and skeletal analyses.  In addition, diachronic comparisons of diet are possible.

STATISTICAL MODELLING OF ECOLOGICAL SIGNALS: A NEW METHOD FOR DEVELOPING ORE ROBUST APPLICATIONS OF PALAEOENVIRONMENTAL INTERPRETATIONS ON AN INDUSTRIAL DATASET

Geology Dept., University of Oslo, PB 1047 Blindern, N-0316 Oslo, Norway

GeoResearch Consulting, 2100 Skarnes, Norway

Statoil, Furusbeen 50, N-4035 Stavanger, Norway

Previous work by B. Dale and co-workers has developed methods for statistical modelling of ecological signals (SMES) from present-day dinocysts. Here we report the first test of their application to industrial biostratigraphy – on a palynology dataset provided by Statoil. The dataset was from 4 wells along an onshore-transect from the Norwegian North Sea.  The data available was semi-quantitative (c. 100 specimens per sample counted and the remainder of the slide scanned) and all counted by the same contractor (taken from a multiwell study) for consistency.  The wells were part of a larger study on palaeoenvironments completed by Statoil on approximately 48 wells. Some of the traditional multivariate statistical methods had been tried but without success.  The abundances of individual species (usually the marker species for regional flooding surfaces as these were present in varying numbers as opposed to being only rare) were plotted for each well along an offshore/onshore transect for each time slice, and similarities between the profiles were noted and mapped.  Using a proposed model, these similarities were then compared with the seismic facies and environmental maps presented.  The palaeoenvironment was thus partly understood from the larger previous study, allowing the SMES method to be tested against a control method.

The SMES application was tested "blind" (i.e. with no prior knowledge of the age of the sediments, location of the wells, or results from the larger Statoil project). Correspondence analysis was run on the dinocyst data from each well. The resulting plots showed clear, and consistent spreads of species along the first two axes, allowing the identification of the statistically most important species, and their relative positions along the two statistically most important suggested ecological trends. Tracking these species down-hole revealed a consistent pattern of changing relative values between these two ecological trends, allowing the identification of major shifts between the two at various horizons. Two major shifts were identified in each well that could be correlated between all four wells. Comparing the patterns of distribution of species along the main axis suggested this to probably represent the nearer-shore/oceanic signal of Dale (1996). This interpretation allowed us to: 1) Suggest the orientation of the well sites relative to a paleo-shoreline, and 2) To identify the major ecological shifts down-hole as expressions of transgressions/regressions. The final comparison between these interpretations and Statoil results was very encouraging – the suggested orientation of the wells agreed with their positions interpreted from the larger regional study, and the major ecological shifts from the SMES application corresponded exactly to the Statoil flooding surfaces. This first test strongly suggests these methods to offer a much quicker, and more robust application for palaeoenvironmental interpretations from the dinocysts in biostratigraphic datasets.

FUNGAL SPORES FROM COPROLITES: A MEANS OF DETECTING HERBIVORE DENSITY

O.K. DAVIS

Arizona-Nevada Academy of Science, & Department of Geosciences, University of Arizona, Tucson, AZ 85721-0077 USA

During the historic period, spores of the dung fungus Sporormiella are abundant in lake and cave sediment where livestock are plentiful in the western United States. Sporormiella spores often exceed 50% of the upland pollen sum in samples from corral ponds and bed-grounds, and routinely reach 2-3% in lake and marsh samples in pastoral areas.

Sporormiella spores are comparatively rare during the Holocene, but they reach values of 2-4% in Pleistocene samples from lake sediments. Sporormiella spores are directly linked to extinct megaherbivores by their presence in mammoth dung from Bechan Cave, Utah. A precipitous decline of Sporormiella percentages after 10,800 yr B.P. apparently marks a decline of herbivore density in lake cores from Idaho, Colorado, and other sites in the western United States.

THE SCIENCE OF COPROLITE ANALYSIS: THE VIEW FROM HINDS CAVE

G.W. DEAN

Historic Preservation Division, Office of Cultural Affairs (Rm 320), 228 E. Palace Ave., Santa Fe, NM 87501 USA

Nearly a century of human coprolite analysis includes specimens from all over the world and from the dawn of human existence onward. Analytical techniques have evolved with successive generations of researchers willing to explore the ecology of the fecal deposit. Archaeological analyses in the New World, particularly Peru and the North American Southwest, are especially noteworthy due to excellent preservation of sometimes enormous numbers of specimens from single archaeological sites.

My 1978 analysis of 100 specimens from perhaps the first identified prehistoric latrine in North America is a case in point. These specimens represent about 10% of an archaeological deposit with bracketed dates of 5710 +/- 80 and 5590 +/- 80 radiocarbon years before present (uncorrected) from the top and bottom of the deposit, respectively.

The analysis of these 100 specimens provided detailed data on the contents: pollen spectra, plant remains, insect remains, animal bone and fur, and attempts were made to find evidence of intestinal parasites, occult blood residues, viruses, and most recently, sex hormones. An experiment, conducted with volunteers as part of the archaeological analysis, produced 82 modern specimens yielding data on the rate of elimination of specific pollen grains from the human system.

Subsequent coprolite analyses in the American Southwest have focused on fewer specimens from any given time period. Some ideas, such as using pollen concentrations as an indication of recent ingestion, are largely untested for validity. Unwarranted assumptions have also crept into this most anthropological of sciences.

This paper provides new perspectives resulting from my re-examination of my 1978 pollen data. Of particular interest are the results of pollen concentration calculations for both the prehistoric and the modern specimens, and the results of a test to determine the minimum number of coprolites that must be examined to reach a degree of redundancy of data.

The 1978 study remains the most comprehensive analysis of such a large sample of coprolites from a single archaeological site and time period. Yet, this paper shows that there is ever more to learned from these and other coprolite specimens. The application of specialized techniques at the microscope, such as Intensive Systematic Microscopy, to locate and quantify rare pollen types needs to be explored. Parasitological studies of human coprolites will benefit from experimental data to determine the fate of the constituents of human feces ingested by dogs. Easy and valid ways to express the abundance of macroremains in a coprolite are also needed.

PALYNOLOGICAL CALIBRATION AND CONFIRMATION OF A SEQUENCE STRATIGRAPHIC/SEDIMENTOLOGIC MODEL FOR THE OFICINA FORMATION (EARLY MIOCENE) AT PETROZUATA, VENEZUELA

T.D. DEMCHUK

Conoco Inc., Integrated Interpretation Center, Houston, TX 77252-2197, USA

Consultores Geostrat C.A., Los Altos de Santa Fe, Via Principal, Sector el Saco, Villa El Eden, Edo Sucre, Venezuela

Conoco Inc., Integrated Interpretation Center, Houston, TX 77252-2197, USA

Palynological assemblages are most valuable data for the recognition and calibration of sequence stratigraphic systems tracts, and for the confirmation of depositional paleoenvironments as interpreted from sedimentological observations, seismic facies analyses and wireline log stacking patterns. Reservoir strata of the Oficina Formation from Petrozuata, are a highly complex amalgamation of deltaic, estuarine, and fluvial paleoenvironments. Sandstone bodies are vertically and laterally variable, and the recognition of this variability in the subsurface based on integrated stratigraphic models is critical to a successful drilling program and hydrocarbon exploitation. Palynological analyses of the shales within reservoir intervals, and the resulting assemblages helps formulate palynological "fingerprints" which can then lend confirmation to sedimentological observations. This palynological fingerprint is an interpretation of the paleoecology based on the pollen, spore, and dinoflagellate content of the assemblage. Subsequently, these varied palynological fingerprints can aid in the development and confirmation of a sequence stratigraphic model through the recognition of highstand and associated maximum flooding surfaces and the identification of systems tracts.

Reservoir strata of the Oficina Formation at Petrozuata are early Miocene in age, Verrutricolporites rotundiporus Zone, Psiladoporites minimus Subzone. Generally, palynofloral assemblages contain abundant freshwater pollen and varied spores (Verrucatosporites usmensis) with sometimes dominant palm pollen (Mauritiidites sp.). Variations in the relative abundances of terrestrial pollen, versus mangrove pollen and dinoflagellates are characteristic of the varied paleoenvironments of this prograding paralic succession. At least four major flooding surfaces are recognized palynologically within the main reservoir interval, and these can be calibrated to third-order cycles on the worldwide sea-level chart. These flooding surfaces are characterized by high abundances of mangrove pollen (predominantly Zonocostites ramonae) as well as varied dinoflagellate taxa including Cribroperidium tenuitabulation, Lingulodinium machaerophorum, Spiniferites sp., and Hemicystodinium zoharyi. Dinoflagellates are ubiquitous in the majority of palynological assemblages, with the exception of those from the lowermost sequences of the reservoir interval. The quantity and low diversity in the majority of these assemblages indicate a nearshore, inner neritic setting. However, a maximum flooding surface dated at 18.0MaYrs is of great regional extent suggesting that during this time the entire Petrozuata area was completely inundated by marine waters. Lateral variations in these high abundance, high diversity dinoflagellate assemblages characterizing this maximum flooding surface indicates paleowater depths of middle neritic in the northeastern portion of the Petrozuata property.

DATA INTEGRATION AS THE KEY TO ROBUST RESERVOIR MODELS

C.N. DENISON, R.C. PREECE

EPTC, ChevronTexaco, San Ramon, CA, USA

Creation of a viable reservoir model should bring together a multiplicity of differing sub-surface disciplines. Data assimilation, integration, and iteration are the keys to effective reservoir modeling. Examples are presented to illustrate some of these aspects.

Industry experience is that history matching varies significantly: reservoir models of producing oil fields may not flow. Reservoir engineers have to resort to data manipulation, typically gross changes to permeability, porosity and faults, to force a history match, but this results in progressive divergence from reality into the future.

Understanding the flow-unit geometry within the reservoir relies upon a robust stratigraphic framework that is based on 1D well picks and core-based depofacies, then expanded to 2D well log correlation panels, using sequence stratigraphic concepts. Failure to accurately capture the subsurface architecture at this initial stage renders all subsequent work moot. Detailed core description and correct depofacies identification is operator-dependent, but in common with other basic geological disciplines, there is a shrinking expertise base.

Sequential Gaussian Simulation is one method for populating the 3D inter-well space, but typically generates a salt-and-pepper property distribution that is geologically unsatisfying. Object-based modeling, the creation and distribution of 3D objects, produces a more realistic and geologically satisfying model of internal reservoir complexity. Constraints on the dimensions and properties of the objects ultimately depends on our knowledge of modern processes and outcrop analogs.

Essential to generate and test a reservoir model are Dynamic Engineering Data, the large number of continuous measurements taken during oil-field development and production. Datasets such as original pressures and temperatures, pressure declines, individual well production history, and water-cuts have to be logically reconciled with the stratigraphic model.

Modern 3D seismic surveys can produce remarkable stratigraphic resolution, but at the reservoir scale there is often something lacking, due to a variety of factors such as acquisition and processing problems, depth to reservoir, or simply the inherently low vertical seismic resolution. Despite these limitations, 3D seismic is the only volume-based dataset, and has to be integrated into a robust reservoir model.

Biostratigraphy plays a small but important role. Standard biozonation scales restrict their application to exploration activities: few reservoirs span sufficient time for standard biozones to be useful. At the reservoir scale, various methods have been developed, mainly based on the ecozone concept for field-wide correlations. Predictable properties from this approach are leveraged into the reservoir model. The future of applied biostratigraphy depends on electronic database interface, the ideal platform for deployment of interpreted biostratigraphic data into the reservoir characterization domain.

UPPER MIOCENE – PLIOCENE SUBSURFACE PALYNOLOGICAL REFERENCE SECTION FOR THE CRUSE, FOREST AND MORNE L’ENFER FORMATIONS, FOREST RESERVE FIELD, TRINIDAD, WEST INDIES

L. DE VERTEUIL

Latinum Ltd., P.O. Box 575, Port of Spain, Trinidad, WI

Geological Services Laboratory, Petrotrin Ltd, Pointe-à-Pierre, Trinidad, WI

The Cruse, Forest and Morne L'Enfer formations represent the upper Miocene – Pliocene proto-Orinoco deltaic succession in the onshore southwest Southern Basin of Trinidad. Prior to offshore discoveries this was the main oil producing area of Trinidad and remains both geographically and stratigraphically central in studies of the upper Neogene regional geology. The giant Forest Reserve Field produces from Cruse and Forest reservoirs, with cumulative production of over 275 mbbl of oil.

One hundred and twenty-nine conventional core samples, from an overlapping, continuously cored interval from wells FR670 and FR691, provide the basis for the present study. The FR670/691 composite contains a co-type Cruse section, the type section of the Forest Formation and a representative lower Morne L'Enfer section. A further 115 core and cuttings samples from four additional Forest Reserve wells compliment and provide lateral control on data from the FR670/691 section, including an upper Morne L'Enfer interval. Hopping's earlier analysis of the FR670/691 section was integral to the pioneering pantropical palynological studies by Shell. The present fully composited section from Forest Reserve spans the Grimsdalea magnaclavata, Pachydermites diederixi, and Echitricolporites mcneillyi Caribbean intracontinental zones of Germeraad, Hopping and Muller (1968).

Quantitative palynomorph and palynofacies analyses, integrated with e-log facies and core descriptions, permit re-evaluation and refinement of existing regional zonations within a sequence stratigraphic framework. At the field scale, the delineation of acme events and taphonomic/paleoenvironmental interpretation of the assemblages contributed to overall reservoir characterization.

The transition from calcareous basinal Lengua Formation shaley marls to essentially non-calcareous Lower Cruse Clay, representing the distal edge of the advancing deltaic system, is transitional over ca. 45 m (150 ft). This transition is characterized by decreasing dinocyst abundance, particularly of the offshelf genera Impagidinium and Nematosphaeropsis, within a palynofacies still dominated by marine amorphous SOM. Above this marine clay, the Lower Cruse – Middle Cruse unconformity represents the most significant basinward shift in palynofacies and depositional environments observed in the study, heralding the arrival of the Orinoco system in the Forest Reserve area. Above this level, five major sequences (S-0 – S-4) are delineated, generally corresponding to the Middle Cruse, Upper Cruse, Forest, Lower Morne L'Enfer and Upper Morne L'Enfer.

ANALYSING THE INTESTINAL CONTENTS OF ANCIENT ICEMEN (ÖTZI AND LONG AGO PERSON FOUND): REVEALING ITINERARIES AND DOMICILES

J.H. DICKSON

University of Glasgow

Geological Survey of Canada, Dartmouth, Nova Scotia

Royal British Columbia Museum, Victoria, British Columbia

VARIATIONS IN UPPER OLIGOCENE – LOWER MIOCENE DINOFLAGELLATE CYST ASSEMBLAGES AND THEIR RELATIONSHIP TO GLACIO-EUSTATIC SEA-LEVEL CHANGES, ONSHORE JYLLAND, DENMARK

K. DYBKJÆR

Geological Survey of Denmark and Greenland (GEUS), Thoravej 8, DK-2400 Copenhagen NV, Denmark

A sequence stratigraphic subdivision of the Upper Oligocene – Lower Miocene siliciclastic succession in the central parts of Jylland, Denmark, has been recently published. The variation in the dinocyst assemblages in the lower three sequences, A-C, is presented here, and the response to eustatic sea-level changes is discussed.

Sequence A (latest Chattian) shows a rich and diverse dinocyst assemblage in the lower, fully marine part (the TST). In the upper, gradually shallowing part (the HST), the dinocyst abundance and diversity decreases while the relative abundances of freshwater algae and non-saccate pollen increases. Deflandrea phosphoritica shows a distinct increase in abundance towards the upper sequence boundary, possibly as a result of increased nutrient supply. Furthermore, in the most proximal parts of the study area, Homotryblium plectilum appears in the uppermost part of the sequence.

Sequence B (latest Chattian? – early Aquitanian) was deposited in a restricted marine, low salinity environment. The dinocyst assemblage is dominated by Homotryblium spp., Dapsilidinium pseudocolligerum and Spiniferites spp. Within the genus Homotryblium, a lateral variation in the distribution was found, with H. plectilum being most abundant in the proximal parts of the study area (possibly reflecting a high freshwater influx) while H. tenuispinosum dominated the more distal parts of the study area (thought to be less influenced by freshwater).

A major unconformity is present between Sequences B and C. Sequence C (early to mid-Burdigalian) was deposited in a more open marine, probably shelfal environment. The dinocyst assemblage is generally characterized by a dominance of Spiniferites spp., Operculodinium centrocarpum, Impletosphaeridium insolitum and Systematophora placacantha. Furthermore, the more open marine conditions are clearly reflected in a higher abundance and diversity of dinocysts. Several new species appear, while Homotryblium spp. only occurs sporadically except for in the most proximal areas where this genus is common.

The datings of the studied sequences have been compared with earlier published curves of eustatic sea level variations based on variations in oxygen isotopes, and with inferred glacial maxima. The close correlation between these data strongly indicate that eustatic sea-level changes were the main controlling factor on the observed changes in the depositional environment and in the dinocyst assemblages. Local structural elements, however, also influenced the depositional environment both by acting as discrete topographic barriers and also by controlling the location of spit development.

DINOFLAGELLATE CYSTS FROM THE CHESAPEAKE BAY IMPACT STRUCTURE – IT WAS A BLAST!

L.E. EDWARDS

U.S. Geological Survey, 926A National Center, Reston, VA  20192 U.S.A.

The Chesapeake Bay impact structure was formed by a comet or meteorite that struck the continental shelf of the eastern United States (southeastern Virginia) about 35.5 million years ago.  As in other sites with a marine sedimentary target, the resultant impact-generated breccia consists of rocks and sediment that were present at the time of impact, which were then redeposited under conditions that include various combinations of shock, heat, collapse, tsunamis, and airfall.  Impact-generated deposits within the crater contain dinoflagellate cysts that are fused, curled, folded, bubbled, broken, pitted, and (or) partially melted.

Samples from the impact-matrix deposits contain Cretaceous to late Eocene dinocysts.  Late Eocene dinocysts such as Cordosphaeridium funiculatum and Batiacasphaera baculata are coeval with the impact.  Older specimens, most abundantly Pentadinium goniferum, Pentadinium membranaceum, and Dracodinium varielongitudum, were derived from older units in the Virginia Coastal Plain and redeposited into these younger, impact-related deposits.

The preservation of the dinocysts and other palynomorphs in the impact-matrix material is striking.  Most notably, the overall preservation would be categorized as poor. In some instances, one can recognize material of dinoflagellate origin, but cannot identify it to species or even genus or family.  Fragments are much more common than whole or nearly whole specimens and organic debris tends to occur in fused clumps.  But the adjective "poor" does not adequately reflect the wide variety of impact-related damage imparted on the specimens.  I will illustrate the most prominent preservation types.

The alterations of dinocysts in impact-matrix deposits constitute a relatively unstudied aspect of taphonomy.  In this case, Cretaceous, Paleocene, and Eocene dinocysts have experienced two episodes of deposition.  During the latter episode, in late Eocene time, the events that preceded final burial included heat, shock, abrasion, and in some cases, airfall.  Altered dinocysts are also found in post-impact deposits as young as late Miocene (27 million years after the impact). These specimens were exhumed and deposited yet again, perhaps reflecting movement along compaction-related faults.

Fused, folded, partially melted, or bubbled microfossils, together with broken cysts, may offer new insights into cratering mechanics, and the specific kinds of damage (heat vs. shock-induced breakage) may provide important constraints to the understanding and interpretation of the crater history.  Furthermore, since these altered microfossils come from a known impact structure, they may serve as guides for recognizing impact-related deposits elsewhere.

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.

FORGING A PATH FOR BIOSTRATIGRAPHY

M.B. FARLEY

Geology, BA 206, University of North Carolina at Pembroke, Pembroke, NC 28372, USA

Biostratigraphy’s future depends on recognizing what we have accomplished in academia and industry, building on that base, and effectively marketing our technologies and knowledge to the broader scientific and industrial community.

In micropaleontology, 40 or more years of concentrated effort has led to valuable technology as well as important spin-offs outside biostratigraphy and even outside paleontology.  We have a general global stratigraphic framework from continents to deep oceans in the Phanerozoic.  In some basins, we have biostratigraphies with average resolution at 100 ky or better.  In addition, our work has been vital to development of information on phylogenetic pattern and mode, paleoenvironment, and basin thermal history.

Academic micropaleontology has been notably successful at providing a biological context, creation of new techniques such as stable isotope and multivariate analysis, and analysis of high quality sections.  Industrial micropaleontology has provided geological context, integration with new techniques (seismic stratigraphy, well logs), and analysis of dense sections with high potential resolution.

Technical progress depends on improved communication between academic and industrial paleontologists, a standard stratigraphic framework, analysis of all fossil groups together, and improved integration of paleontology with other data.  Technical progress is not sufficient, however.

We need to market biostratigraphy more effectively to the larger geologic and biologic communities.  One important approach is infiltration.  By participating outside paleontology, we can stimulate outside interest in what we can contribute.  A micropaleontologic session is useful within the specialty, but getting our message across to the wider population by appearing in the sessions they attend is equally valuable. Informal infiltration is probably even more important.  We also need to be more aggressive in ensuring that biostratigraphy is more effectively incorporated in undergraduate and graduate education.

I don’t have all of the answers to successful marketing of the value of our discipline.  This is an area where any paleontologist can make a substantial contribution, and I hope to stimulate thinking about this.

THE STRATABANK^TM CONCEPT – WWW-BASED STRATIGRAPHY WITH LARGE FOSSIL DATABASES

F.M. GRADSTEIN, Ø. HAMMER, N. STÖTZER

Geology Museum, University of Oslo, N-0318 Oslo, Norway

C. CERVATO

Dept. of Geol.& Atm. Sci., Iowa State U., Ames IA 50011, USA

M. SMELROR

Geological Survey of Norway, Trondheim, Norway

R. WILLIAMS, S. FINNESTAD

Norwegian Petroleum Directorate, 4001 Stavanger, Norway

A joint initiative of the Geology Museum of the University of Oslo, leading petroleum companies, and the Norwegian Petroleum Directorate is leading to the creation of the Stratabank^TM system. This new concept is applied to a relational database of all fossil records in all exploration wells from offshore Norway and baptized NORGES – Network of Offshore Records of Geology and Stratigraphy. This economically powerful and scientifically valuable project is the result of over 40 years of highly successful drilling in the Mesozoic and Cenozoic sedimentary wedges in the North Sea, offshore Norway and the Barents Sea. It involves more than 1000 wells spanning over 20 degrees of latitude in the boreal realm. A master dictionary of foraminiferal, dinoflagellate, radiolarian, nannoplankton, diatom, spore and miscellaneous taxa is adding up to over 11000 taxonomic entities, including their junior and/or senior synonyms, and involves over 1000 stratigraphic events. The dictionary may be linked to a digital atlas.

The main advantages of storing such exploration record in a relational database system using Oracle or MYSQL is that it can be probed in an intelligent manner. It must be remembered that different operators and a variety of European consultants generated the fossil distribution charts and events. The resulting record is non-standardized and can be idiosyncratic and noisy. Its digitization is a slow and tedious manual job, executed as soon as the well records are released to the public after two years. In-house binary consultant taxonomy must be standardized with the help of exploration stratigraphy manuals, and suspected caving records must be tagged.

With the help of modern tools like age vs. depth diagrams, burial graphs that also cumulate paleo-water depth, regional chronograms tied to the standard time scale, and correlation charts with events of higher stratigraphic fidelity, the relational record is made useful to both exploration stratigraphy and to scientific studies of basin dynamics. Intelligent database access and expertise to translate the fossil record stratigraphically and paleobathymetrically is one of the key issues with such WWW-based records that the Stratabank^TM concept is capable of offering exploration biostratigraphers in this new millennium.

DID SHEEP/GOAT EAT UP THE NEOLITHIC FOREST? – PALYNOLOGY OF SHEEP/GOAT FAECES FROM PREHISTORIC PILE-DWELLINGS OF SWITZERLAND

J.N. HAAS

Department of Botany, University of Innsbruck, Sternwartestraße 15, A-6020 Innsbruck, Austria

A review of the pollen and macrofossil content found in prehistoric sheep/goat dung pellets from pile-dwelling sites in Switzerland reveals interesting foddering trends towards understanding prehistoric agricultural techniques during the Neolithic Period (4300-2200 BC):

1. Most faeces analysed palynologically represent fodder consumption in winter or early spring near or within the former settlements.

2. Leaves and twigs of wintergreen plants such as Rubus fruticosus s.l. and Abies alba were an important fodder resource.

3. Additional foddering with early flowering twigs from shrubs such as Corylus avellana and Alnus spec. was done in early spring in times of shortage.

4. Foddering of goat/sheep with food garbage (e.g. cereal grains or cereal waste products) seems to have been the exception during prehistoric times.

5. Winter-Foddering of prehistoric goat/sheep with dry tree leaves and twigs gained by pollarding or shredding in the previous summer (e.g. Tilia spec. or Ulmus spec.) was obviously less common than known from historical times.

All in all, the foddering techniques used for goat/sheep during the Neolithic and Bronze Age Period point to the direct use of all available plant resources in winter and early spring. The results do not support the idea and historically known tradition that large quantities of plant fodder were stored in late summer and autumn for such animals in order to have enough fodder in winter. However, such an agricultural technique might have existed prehistorically for larger livestock, such as cows.

THE ORIGIN OF LOWER DEVONIAN SPORE-RICH COPROLITES

K. HABGOOD

Dept. Earth Sciences, Cardiff University, P.O. Box 914, CF10 4YE

Small (less than 5mm long), spore-rich coprolites are common in certain Upper Silurian and Lower Devonian horizons within the lower Old Red Sandstone group. Two L. Devonian assemblages of terrestrial fossils, one preserved in fluvial sedimentary rocks in the Welsh Borderland and the other in the siliceous Rhynie Chert from Aberdeenshire, include unusually abundant and diverse coprolites.

The two assemblages, although similar in age and both preserved amongst plant fossils and organic debris, differ significantly in preservation and taphonomy. Coprolites from the Welsh Borderland are coalified and relatively compressed, and preserved in transported sediments. Conversely fossils silicified within the Rhynie Chert were preserved more rapidly and much closer to their source if not in situ. Coprolites from both sites are diverse in morphology and content, and comparison of the two assemblages reveals interesting differences, but in each case spore-rich coprolites comprise a significant proportion of the total faecal assemblage, and spores contained within the coprolites are apparently well-preserved and relatively rarely damaged.

Spore populations present within faeces from these assemblages provide clues to the nature of the coprolite-producing fauna and their diet. This and further evidence, ranging from the nature of the primary productivity available to Lower Devonian terrestrial fauna, to the results of experimentation using modern analogues, suggest that spores may not have provided a good source of nutrient for early terrestrial animals, and point to other origins for these spore-rich coprolites.

EXPRESSIONS OF SEQUENCE PALYNOSTRATIGRAPHY FROM THE GREENHORN MARINE CYCLE (CENOMANIAN-TURONIAN) OF THE WESTERN INTERIOR BASIN, USA

A.J. HARRIS

School of Applied Sciences, University of Glamorgan, Pontypridd, Mid-Glamorgan, CF37 1DL, UK

The wealth of geological data on the Cenomanian-Turonian sequences from the Western Interior Basin allow a highly-integrated analysis of the palynostratigraphic expressions of eustatic and associated environmental fluctuations. As these sequences were deposited in an actively subsiding foreland basin, their study offers a number of advantages over other sequences of equivalent age. Numerous dated bentonites allow high-resolution (bed-by-bed) correlation between sections some hundreds of kilometres apart, and provide a detailed chronostratigraphic framework. Limestone-shale couplets (of Milankovitch origin) from the eastern pelagic carbonate ramp and central hemipelagic trough are correlatable with marginal-marine and proximal parasequences deposited at the rapidly subsiding western basin margin. High-resolution chronostratigraphic comparisons of dinoflagellate cyst species from these very different marine environments across the seaway have allowed them to be associated with water temperature, salinity, shoreline-proximity and bathymetry.

The Greenhorn cyclothem (Lower Cenomanian-Middle Turonian) was deposited within the Western Interior Basin over a second-order eustatic cycle, at a time of global first-order highstand. The environments studied from the Amoco Rebecca Bounds Core from Kansas, range from marginal marine through proximal to distal shelf environments within the transgressive systems tract, and return to a proximal shelf environment in the highstand systems tract. Dinoflagellate cyst assemblages are indicative of these environments and support models for circulation in the epicontinental seaway that linked the boreal ocean to the north with the subtropical Tethys to the south. Superimposed third-order eustatic fluctuations are responsible for lithological (member-scale) variations in the sequences and although at the limits of sampling resolution, can be identified using changing dinoflagellate cyst assemblages.

The Cenomanian-Turonian boundary occurs shortly before a combined first-, second- and third-order maximum flooding interval. A high-resolution study of boundary sections across the basin allows the synchronicity of sequence biostratigraphic events to be assessed in finer-scale sequences and parasequences. Fourth-order eustatic fluctuations forced changes in water-mass characteristics and affected macrofaunal distribution. Their flooding surfaces and progradational highstands can be correlated between proximal and distal shelf environments using the dinoflagellate cyst assemblages. The parasequences/bedding couplets do not show consistent responses in dinoflagellate cyst assemblages but do show characteristic palynofacies fluctuations that suggest variations in terrestrial input to the basin. Dinoflagellate cyst assemblages also aid in the sequence stratigraphic reinterpretation of the lithostratigraphy from marginal/shallow-marine environments.

CARIBBEAN TERTIARY DINOFLAGELLATE ASSEMBLAGES

J. HELENES

Departamento de Geología, CICESE, km 107 Carr. Tijuana-Ensenada, Ensenada, Baja California 22860, México

Sección Geología, INTEVEP, S.A., Apartado 76343, Caracas 1070-A, Venezuela

Instituto Mexicano del Petróleo, Gerencia en Geociencias, Eje Central Lázaro Cárdenas 152, D.F. 07730, México

Tertiary strata from around the Caribbean basin contain four dinoflagellate assemblages assigned to Middle Eocene, Late Oligocene, Early Miocene and Pliocene ages respectively. 

Middle Eocene dinoflagellates have been observed in northwestern Venezuela and include several species of the chorate genera Cordosphaeridium, Glaphyrocysta, Homotryblium, and the proximate taxa Batiacasphaera compta, Cribroperidinium tenuitabulatum, and Lejeunecysta spp. This assemblage is concurrent with the Middle Eocene nannofossils Reticulofenestra reticulata and Chiasmolithus solitus, as well as the terrestrial taxa Bombacidites bellus, Echiperiporites estelae and Spinozonocolpites echinatus. 

Late Oligocene to Pliocene dinoflagellates have been observed in strata from eastern Venezuela and the southern part of the Gulf of Mexico. The Oligocene to Miocene taxa include several species of Homotryblium, Polysphaeridium, together with Cribroperidinium tenuitabulatum and Tuberculodinium vancampoe. The Miocene taxa include Diphyes latisuculum, Spiniferites mirabilis and Hytrichokolpoma truncata, while Pliocene taxa include several species of Spiniferites, together with Multispinula quanta, Votadinium calvum and Hystrichosphaeropsis obscura.

Neogene strata also include calcareous nannofossils, planktonic foraminifera and the terrestrial palynomorphs Foveotriletes ornatus, Crassoretitriletes vanraadshoveni, Kuylipsorites waterbolki, Magnastriatites grandiosus and Polypodiidites usmensis.

These Middle Eocene to Pliocene fossil dinoflagellates from around the Caribbean basin help to reconstruct the geologic development of the area, particularly tracing the eastward movement of the Caribbean plate, separating the North and South American plates.

HIGH RESOLUTION PALYNOLOGY OF THE TARBERT FORMATION (BRENT GROUP, MIDDLE JURASSIC) OF THE NORTH VIKING GRABEN, UKCS

Shell UK Exploration & Production, 1 Altens Farm Road, Nigg, Aberdeen AB12 3FY, UK

Imperial College of Science, Technology & Medicine, Prince Consort Road, London SW7 2BP, UK

BioStrat Ltd, Chapelstone Cottages, Fishthwaite Lane, Backbarrow, Ulverston, Cumbria LA12 8PY, UK

The Tarbert Formation, a shallow-marine sandstone that forms the uppermost unit of the Brent Group in the North Viking Graben, UKCS, has regionally extensive and mappable basal and upper surfaces but displays extremely variable thickness variations. Detailed sedimentological mapping has revealed a wide range of depositional facies with complex interrelationships. A complimentary, high resolution palynology sampling program has revealed a detailed, previously unattained biostratigraphy, elucidating both chronostratigraphic and depositional facies controls and allowing the existing biozonal scheme to be updated and applied in a predictive manner to subsequent analyses of the Formation.

PALYNOFACIES AND STRATIGRAPHY OF THE CYCLIC DEPOSITS OF THE UPPER RHAETIAN KOESSEN BEDS (NORTHERN CALCAREOUS ALPS, AUSTRIA)

B. HOLSTEIN

Geological & Palaeontological Institute, Johann-Wolfgang-Goethe University, Senckenberganlage 32-34, D-60054 Frankfurt am Main, Germany

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

H. Hü >ß ER

Geological & Palaeontological Institute, Johann-Wolfgang-Goethe University, Senckenberganlage 32-34, D-60054 Frankfurt am Main, Germany

Forschungsinstitut Senckenberg, Palaeobotany Division, Senckenberganlage 25, D-60325 Frankfurt am Main, Germany

Institute of Applied Geosciences, Darmstadt University of Technology, Schnittspahnstrasse 9, D-64287 Darmstadt, Germany

The Koessen Beds consist of an alternation of more or less calcareous marls and limestones, which show well-developed transgressive-regressive cycles. These cycles show significant changes of the palynofacies composition. Most samples yielded rich palynological residues including diverse and well-preserved palynomorph assemblages of pollen, spores, dinoflagellate cysts and acritarchs. These assemblages show a typical Rhaetian microflora, including some stratigraphical important pollen, spores and dinoflagellate cysts (Rhaetipollis germanicus, Corollina torosus, Granuloperculatipollis rudis, Riccisporites tuberculatus, Cunaetosporites rhaeticus, Concavisporites sp., Comparodinium koessenium, Rhaetogonyaulax rhaetica).

The pollen/spores assemblages change in their quantitative and qualitative composition and allow a correlation with the palynological zones suggested by other authors (Morbey 1975, Achilles 1981).

The uppermost part of the Eiberg section shows a gradual disappearance of all significant Rhaetian taxa, which may allow to allocate the position of the Rhaeto-Liassic boundary.

QUANTITATIVE BIOSTRATIGRAPHY FOR THE PALEOGENE OF THE LLANOS FOOTHILLS, COLOMBIA: IMPROVING PALYNOLOGICAL RESOLUTION IN OIL EXPLORATION

C.A. JARAMILLO, F. MUNOZ, M. COGOLLO, FELIPE DE LA PARRA

Biostratigraphy team, Instituto Colombiano del Petroleo-Ecopetrol, AA 4185, Bucaramanga, Colombia

>Oil exploration in Colombia traditionally has taken place in areas with relatively few structural complexities.  But in the last decade, exploration has moved to regions characterized by high structural deformation, poor seismic resolution, and many stratigraphic problems, such as the eastern foothills of the Eastern Cordillera.  In this region, the major reservoirs are placed in Paleogene sequences, mostly continental rocks, where palynomorphs usually are the only fossil group used.  Thus, palynology has become a relevant tool in controlling the stratigraphic position of a well during drilling, in testing diverse seismic and structural interpretations, and in correlating to understand reservoir continuity.  However, palynological zonations currently used for the area do not offer the resolution needed and asked for by explorationists. 

Here, we have developed a high-resolution biostratigraphy for the Paleogene making use of quantitative and semi-quantitative techniques such as RASC and Graphic Correlation.  We have used more than 20 sections with palynological information from outcrops, well cores, and well ditch cuttings.  Based on the biostratigraphic model produced by the quantitative analysis, we reinterpret a recently drilled well in the Llanos foothills upon which several previous interpretations have been made.  The results offer a better understanding of the stratigraphy of the well and allow us to make better predictions of the potential reservoir in the area.

FOSSIL INSECT PALYNIVORY AND POLLINATION: ROLE OF PLANT DAMAGE, COPROLITES AND GUT CONTENTS

C.C. LABANDEIRA

Paleobiology, National Museum of Natural History, Smithsonian Institution, Washington, DC 20560, USA; Entomology, University of Maryland, College Park, MD 20742, USA

The fossil record of vascular plant and insect associations contain five types of data that indicate insect consumption of spores, prepollen, and pollen (palynivory) and also address the origin of pollination mutualisms. These types of evidence are, starting from the plant end and containing to the insect end: (1) entomophilous plant reproductive features, (2) insect damage of plant reproductive tissues, (3) matrix dispersed coprolites, (4) insect gut contents, and (5) insect mouthpart and ovipositor structure. Of these, the middle three represent direct effects by insects of plant tissue consumption and provide a significant fossil record documenting the associations between palynivorous insects and vascular plants from the earliest land ecosystems to the recent. Accordingly, four distinctive assemblages of vascular plant/palynivore associations characterize the terrestrial fossil record.

The first assemblage occurs from latest Silurian to Middle Devonian and represents basal vascular plant hosts whose animal associates are unknown, but probably were insects or possibly other terrestrial arthropods. The second assemblage is documented from the Middle Pennsylvanian to the Late Permian and represents pteridiphytes and basal seed plants associated with palaeodictyopteroid, hemipteroid, and basal neopteran insects. Plants whose miospores were consumed include marattialean ferns, cordaites, and medullosan and glossopterid pteridosperms, and early gnetophytes, and includes damage to pteridosperm prepollen organs. Interacting insect representatives were members of the palaeodictyopterans, hypoperlids, psocopterans, grylloblattodeans, and possibly orthopterans, and probably were attracted to sugary fluid rewards such as pollination drops, nectaries on vegetative tissues, and honeydew. The third assemblage originated during the Middle Triassic to mid-Cretaceous, but has persisted to the present. Interacting plants include bennettitaleans; cycads; voltzialean, pinacean, and cheirolepidaceous conifers; and advanced gnetaleans. Associated palynivorous or seed-predating insects are prophalangopsid grasshoppers, and more basal lineages of holometabolous insects, such as nemestrinid flies, xyelid sawflies, and nemonychid weevils. Fluid sugar rewards were provided by the pollination drop mechanism and extrastrobilar nectaries. The fourth assemblage is found from the Early Cretaceous to the present, and consists of angiosperms whose associates are predominantly thrips and more derived lineages of holometabolous insects, of which the predominant sugar fluid reward is floral nectaries.
            Hypotheses regarding the origin of pollination have overwhelmingly focused on the phylogenies of extant plant and insect groups, without consideration of an illuminating and relevant fossil record. Importantly, the fossil record documents four assemblages of plant/palynivore associations, of which the first two are extinct, most of the third is gone, and the fourth overwhelmingly dominates the extant biota. Consideration of plant damage, coprolites, and gut contents in the preangiospermous fossil record can provide a crucial perspective for understanding the formative processes and events characterizing the history of pollinivory and the origin of pollination.

PALYNOLOGICAL ANALYSIS OF A 2,000 YEAR-OLD BAT-GUANO DEPOSIT IN WALES (UK)

S.A.G. LEROY

Department of Geography and Earth Sciences, Brunel University, Uxbridge UB8 3PH, UK

Department of Geology, Ulster Museum, Botanic Gardens, Belfast BT9 5AB, N. Ireland, UK

The karst system is very well developed in Wales (UK) and its extension has only been recently explored and mapped. Ogof Draenen, near Blaenavon in southeast Wales, is the most recent major cave discovery (1994) with already > 70 km of passages across a vertical range of 148 m.

With the exception of a small chamber, Siambre Ddu, which lies directly above the main Ogof Draenen system and which is an important roost for lesser Horseshoe (Rhinolophus hipposideros) and a few Greater Horseshoe (Rhinolophus ferruequinum) bats, very few bats have been seen in the main system. Hence, the guano accumulations found in parts of the Ogof Draenen system are unexpectedly large. The heaps, several sqm and > 0.5 m thick, represent volumes unmatched by any other cave system in the British Isles.

A guano sample from Ogof Draenen was radiocarbon dated at 2000 yr ago, placing the sample in the Romano-British period.

Pollen analysis was applied to it as well as nine other samples distributed over the cave at various distances from the presumed entrance and also through the heaps themselves. Comparisons were done to a moss pollster and a mud sample from the area and to two modern guanos from Agen Allwedd cave (5 km to the north-west) which currently is one of the largest active roosts for Lesser Horseshoe bats in Britain and lies close to their present northern limit in Europe.

The main results are:

That most of the Ogof Draenen guano is probably of the same age.

That the modern samples are clearly characterised by the presence of planted trees, invasive plants, and grassland and heathland (vs the fossil samples which reflect a closed forest).

That insect-pollinated plants such as Ilex, Acer, Hedera and Impatiens glandulifera are over–represented in the guano samples.

That various ways of incorporation of the pollen grains to the guano act jointly. Insect eating and grooming by the bat as well as direct air transport by draughts created by temperature difference between the cave and outside take place.

GONYAULAX SPINIFERITES

J.M. LEWIS

Phytosciences Research Group, School of Biosciences, University of Westminster, London, W1W 6UW, UK

Department of Phycology, Botanical institute, University of Copenhagen, Øster Farimsgade 2D, DK-1353 Copenhagen K Denmark

Geological Survey of Canada (Atlantic), PO Box 1006, Dartmouth, Nova Scotia, B2Y 4A2, Canada

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

Department of Phycology, Botanical institute, University of Copenhagen, Øster Farimsgade 2D, DK-1353 Copenhagen K Denmark

Geological Survey of Canada (Atlantic), PO Box 1006, Dartmouth, Nova Scotia, B2Y 4A2, Canada

Department of Oceanography, University of British Columbia, Vancouver, B.C., V6T 1Z4, Canada

The pioneering incubation work of Wall and Dale, some thirty years ago, linked the planktonic Gonyaulax spinifera group to a number of fossil cyst-based genera (Spiniferites, Impagidinium, Bitectatodinium, Nematosphaeropsis, Ataxiodinium, Pentadinium, and Tectatodinium).  Thus began the Spiniferites enigma whereby apparently one motile species could produce cysts referable to several genera.  The question has remained whether cyst-based taxa were overclassified or whether taxonomic distinction of motile taxa was insufficient.  Over 2000 individual isolations of cysts from Spiniferites and related cyst genera have led to the establishment of cultures grown from single cysts of the following cyst-based species: Bitectatodinium tepikiense; Spiniferites elongatus; S. membranaceus; S. ramosus, and a previously undescribed Spiniferites species.  According to the ICBN, genera based on extant forms have priority over genera based on fossil forms; therefore, these cyst-based species are referable to Gonyaulax digitalis, G. elongata, G. membranacea, G. spinifera and G. baltica respectively. (However, the ICBN also allows for retention of the cyst names as morphotaxa.)  Cysts produced in culture showed a wide range of intraspecific morphological variation.  This indicates that cyst-based taxa may be overclassified, but variation is largely along a recognisable continuum; for example, from cysts with no spines to cysts with long spines.  Superficially, morphology of motile cells from different cyst species is similar, however, detailed examination (by SEM) reveals each to be distinct, leading to the conclusion that motile stages were previously underclassified.  Confirmation of this interpretation is supplied by molecular data.  Approximately 1500 base pairs of nuclear-encoded large sub-unit rDNA were determined for G. baltica, G. digitalis, G. elongata, G. membranacea and G. spinifera and the level of sequence variation compared with other Gonyaulacales.  This work showed that the level of genetic variation within cysts recognised as distinct Spiniferites species is high and merits species separation.

DINOFLAGELLATE CYST BIOSTRATIGRAPHY IN THE MIOCENE OF NW GERMANY IN CONTINUOUS CORED WELLS

J.J. LUND

RWE-DEA Laboratory, D-29323 Wietze, Germany

The boreholes Nieder Ochtenhausen and Wursterheide, located 46km from each other in NW Germany, yield the thickest Middle to Upper Miocene sections ever cored in or near the North Sea. They were drilled by the Geological Survey of Lower Saxony for a multidiscipline investigation. A major advantage of such sections, compared to the small isolate outcrops available in NW Germany, is that the succession of microflora is clear.

Dinoflagellates were analysed from 84 samples of Nieder Ochtenhausen representing 99m of Miocene section and the occurrences of 86 taxa presented on a semi-quantitative chart recently published (Strauss et al., 2001). Based on these data and dinoflagellate cyst ranges in the Danish Gram borehole with Lower Miocene a new zonation scheme was proposed. It is an extension of J. Powell’s 1992 scheme which had to be adjusted to incorporate new index taxa (Coustadinium aubryae ssp. gonoperforata, Palaeocystodinium miocenicum, Cannosphaeropsis passio) and to take into consideration new information on the first stratigraphic appearance of Amiculosphaera umbracula. Cannosphaeropsis passio is an important marker in the higher Middle Miocene dated by other means in the Gro ß Pampau well. Contrary to earlier opinions, the genus Palaeocystodinium ranges into the deeper Upper Miocene, but differentiation of species helps to distinguish Upper, Middle and Lower Miocene. The occurrences of Hystrichosphaeropsis obscura and Selenopemphix armageddonensis overlap in the higher Upper Miocene indicating a stratigraphically more complete sedimentary succession than from eastern North America.

55 samples from Wursterheide well, representing 185m higher Lower Miocene to Upper Miocene were analysed by C. Heilmann-Clausen, and a correlation with Nieder Ochtenhausen was published (Lund & Heilmann-Clausen, 2001). The correlation is straightforward and unproblematic in the higher Lower to Middle Miocene but complicated in the Upper Miocene where Achomosphaera ramulifera is recognised as a biostratigraphically important species. The correlation reveals that some dinoflagellate events are missing at a hiatus at ca. 261m in Wursterheide. The missing section corresponds to the interval 90-110m in Nieder Ochtenhausen. The hiatus is probably due to a sea level drop at, or near the boundary between the Middle and the Upper Miocene.

The upper boundary of the Miocene is problematic in both discussed wells. H. obscura is present but the large and characteristic Impagidinium "densiverrucosum", which occurs in the microfaunally dated Pliocen-Miocene transition of the Ems Area and is tentatively used to mark the top of the Miocene in the southern North Sea, could not be found.

ENVIRONMENTAL INFORMATION FROM THE PALYNOLOGY OF BAT GUANO

L.J. MAHER, Jr

Department of Geology and Geophysics, University of Wisconsin, 1215 W. Dayton Street, Madison, WI 53706 USA

Bat droppings accumulate in caves, and the resultant guano contains a stratigraphic record of the environment analogous to the record from lake sediment and peat. The bats forage at night for insects over a particular area, and they return to the cave during the day to sleep and care for their young. They attach themselves to suitable perch areas of the cave ceiling, and their excrement accumulates on the floor below.  Flying requires a lot of energy, and this requires the bats of temperate regions to consume large numbers of night-flying insects.  In some situations the guano can reach a depth of meters in hundreds to thousands of years, and it has a valuable chronostratigraphy. The bat scats occur as small pellets that individually represent the non-digestible portion of the animal's diet in the preceding day; hence the diet provides information about the time of the year the feeding occurred.  Bat guano contains, among other things, insect fragments, hair, pollen, and some mineral matter.  Night-flying insects do not normally visit flowers for the pollen; many species do not eat during the flying phase of their life cycle, and those that do generally are nectar feeders.  Although the insects are not after the pollen, they do fly through a pollen-laden environment, and the pollen and dust adheres to their bodies.  The insects essentially act as living traps for airborne debris.  The bats also are furry pollen traps; during grooming they ingest pollen and dust enmeshed in their fur, and this also is excreted.  Study of the pollen in an individual scat contains a record of the atmospheric pollen during a single day in the past.  Pollen from multiple scats can provide a record of a season.  This kind of detail is hardly ever available from lake sediment.

Chemical analysis of individual bat scats in a time series can provide a record of the region's changing environment caused by agriculture, industry, volcanic dust, and a host of other details that depend only on the cleverness of the researcher.  Careful carbon-14 analysis can isolate times when bats did not use the cave, and that negative evidence can also be used to interpret past conditions.  If the types of insect in the guano change over time, that may also provide evidence of changing climate.

Tom Aley, owner of the Ozark Underground Laboratory, Protem, Missouri, USA, allowed me to collect guano samples for an exploratory study.  Tumbling Creek Cave con­tains a maternal colony of the Grey Bat (Myotis grisescens) that occupies the cave for a short time each year.  Scats collected from the base of a 75-cm thick cone of guano yielded an AMS ¹⁴C date of 2810 ± 40 (CAMS 85667). The fecal material has a crumbly structure below the surface; it was of mahogany color (7.5 YR 2/1 to 3/2) and had no noticeable odor.  The feces contained many insect fragments, hair, and a wide assortment of pollen and spores.  Guano can be pro­cessed like normal sediment, but simple washing in a weak detergent solution followed by acetolysis appears adequate. Normal sediment coring devices compress the guano; this can be avoided by using a modified "Russian" peat sampler or by freezing the guano to a dry-ice-cooled probe.

ARTHUR RAISTRICK: BRITAIN’S PREMIER PALYNOLOGIST

J.E.A. MARSHALL

SOES, Southampton Oceanography Centre, Southampton, SO14 3ZH. UK

Arthur Raistrick undertook pioneering palynological research at the very start of the systematic study of fossil pollen and spores. At that time his research interests were in both glaciation and coal geology. His contribution was to adopt the method of pollen profiling in peat to coal seams. Firstly he developed a robust method for the routine extraction of palynomorphs from coal. He then devised a binomial letter/number system to name the palynomorphs. Initially his approach was to profile the coal seams followed by characterizing the entire seam by use of a channel sample. This proved that the same coal seam had the same palynological content and was different from other coal seams. He tested these methods on a number of coal seams at a large number of collieries in northern England. This gave pre-Quaternary palynology both a scientific basis and an immediate commercial application. With onset of the WWII he withdrew from palynology never to return.

PALYNOLOGY AND MATURITY STUDIES IN A STRUCTURALLY COMPLEX TERRAIN: THE DEVONIAN OF BOLIVIA

J.E.A. MARSHALL

SOES, Southampton Oceanography Centre, Southampton, SO14 3ZH, UK

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

Department of Geology, Trinity College, Dublin 2, Ireland

Ichron Ltd, Northwich, Cheshire, CW9 7TN

A significant proportion of the hydrocarbons in Bolivia are found in the sub-Andean zone. This is a fold and thrust belt immediately east of the main Andean range. The local Devonian stratigraphy comprises from top to bottom; the Los Monos, Huamampampa, Icla and Santa Rosa formations. The sandstone dominated Huamampampa and Santa Rosa formations form the main reservoir intervals. Differentiating these reservoirs in intervals where they are commonly repeated and are complexly interthrusted with shaley/silty facies of the Los Monos and Icla has to date been unsatisfactory being mainly based on log response and existing structural models. These difficulties are compounded by the lack of definition in the seismic exacerbated by the presence of low angle thrusts.

The wells are deep and many drilling problems have been encountered. Recovery of either core or full log suites has often been difficult. The palynomorph assemblages are generally of low diversity and are frequently thermally very mature. However, successful field development still requires the development of integrated structural and stratigraphic models based on these wells.

The key to developing the stratigraphic framework from which the model is developed model is the recognition of a number of discrete palynological events. These are pulses of distinctive acritarchs typically in high abundance but low diversity. This permits a number of correlative levels to be recognised. These frequently show that there is a previously unrecognised structural repetition of the succession. In order to detect the location of these, generally low angle, faults a combination of dip-meter and thermal maturity measurements are combined with log interpretation. The thermal maturity measurements are made using a selection of materials. The preferred being chitinozoans, which are easily recognised in polished section. Other organic matter measured includes sporinite, vitrinite and cutinite. The low angle faults are detected by the sudden jumps in thermal maturity often with short sections of reversed gradient. Non-organic means of measuring maturity specifically through the study of clay minerals has also been undertaken and calibrated against chitinozoan, cutinite and vitrinite reflectivity data.  These integrated palynological and thermal maturity methods enable the stratigraphy in the wells to be determined which then constrains the structure as interpreted from the seismic lines.

PALYNOLOGICAL EVIDENCE FOR CRUSTAL SUBSIDENCE DURING LATE HOLOCENE EARTHQUAKES IN COASTAL BRITISH COLUMBIA, CANADA

R.W. MATHEWES, J.F. HUGHES

Department of Biological Sciences, Simon Fraser University, Burnaby, B.C., V5A 1S6 CAN

Various palaeoecological techniques are being used to identify past earthquakes on the Pacific Coast of North America, and reconstruct their frequency.  Tree rings, foraminifera, and diatoms are all being used to estimate the timing and effect of coseismic changes within the Cascadia subduction zone, which experiences occasional great (> magnitude 8) seismic events, as well as frequent smaller quakes.  The analysis of pollen from coastal marsh sediments is shown to be a useful technique for estimating the amount of crustal subsidence associated with major earthquakes.  This information is critical for checking the estimates using other techniques, and ultimately for building better geophysical models of crustal strain accumulation and release.

Palynological studies have identified past coseismic subsidence in buried marsh soils near Vancouver, B.C., a large metropolitan area on the Fraser River Delta.  Rapid burial of coastal soils due to subsidence is accompanied here by evidence of liquefaction and drowned trees.

The best data for estimating the actual amount of coseismic subsidence comes from the Tofino area of western Vancouver Island, where the most recent subduction zone earthquake occurred in A.D. 1700, leaving a tsunami sand sheet as well as buried soils.  The sand is overlain by intertidal mud which grades up into the present-day marsh.  Elevational studies of modern marsh plant communities were combined with analyses of pollen in surface samples and buried sediments.  Pollen analysis shows that a high marsh, with pollen of Poaceae, Potentilla, Achillea type, and Angelica type existed at the head of English Cove prior to the 1700 quake.  This assemblage was suddenly replaced by low marsh vegetation with Cyperaceae, Chenopodiaceae and Triglochin.  Comparison of these buried assemblages with modern analogue elevations suggests that the amount of subsidence was approximately 0.6 m, corresponding well to estimates using fossil foraminifera from the same area.