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Gamel El-Ghazaly and John R. Rowley
The pollen wall of Ephedra foliata was examined by LM, SEM and TEM. The pollen wall consists of three layers: ectexine, foot layer and endexine. The ectexine has a solid tectum underlain by infratectal processes. The infratectal components appear granular in dried grains but there are columellae-like rods in fresh fixed grains that were not subject to dehydration and the elevation of ridges. The Ephedra foot layer is part of the ectexine and has the same contrast. There is a white line lamellation between the foot layer and outer component of the endexine that is probably a junction plane between units of the foot layer and the endexine. The endexine consists of many cylindrical sheets that extend parallel with the long axis of the pollen grain. These sheets appear interconnected and may be branched or recurved in some sites. In pollen that had been acetolyzed the endexine was stained lighter than the ectexine, the reverse of most fresh grains. This is due to the endexine being porous and the material held in it is easily extracted by washing, acetolysis, etc. In dried and acetolized pollen grains the ridges are elevated and the lamellae of the endexine are generally appressed. While in fresh fixed pollen the ridges are flattened and the endexine shows gaps between the lamellae. The intine is thick in fresh fixed mature pollen but we have seen no indication of areas having an exceptionally thick intine that could be considered apertural.
The microsporangium of Ephedra is surrounded by a peritapetal lamellation, as in angiosperms. This lamellation extends between tapetal cells as "tapetal (cell) markers." The orbicules of Ephedra show a lamellation like those of conifers and angiosperms where such a lemellation results from the formative process. Orbicules of Ephedra are generally large and easily removable from the anthers, therefore they could be favorable objects for study of exine chemistry, function and structure.
There is great variation in pollen morphological characteristics such as size, number and shape of ridges and outline of pollen grains from an individual plant and even within a single microsporangium. This would make it difficult to determine affinities of fossil polyplicate pollen with extant species.
Kazumi Matsuoka, Andrew McMinn and John H. Wrenn
Operculodinium centrocarpum (Deflandre & Cookson) Wall 1967 is one of the most commonly reported dinoflagellate cysts (dinocysts) in samples from Tertiary and Quaternary deposits. However, at least two distinct dinocyst morphologies are assigned to this species in the literature at the present time. In addition, two separate species have been erected for one of these distinct morphologies.
In order to define criteria with which to differentiate these morphologies, holotype and topotype material of O. centrocarpum (Deflandre & Cookson) Wall 1967 and O. echigoense Matsuoka 1983 were restudied and compared with dinocysts of Protoceratium reticulatum (Claparéde & Lachmann) Bütschli 1885.
Re-investigation of the holotype and topotype specimens of O. centrocarpum (Deflandre & Cookson) Wall 1967 (=Hystrichosphaeridium centrocarpum Deflandre & Cookson 1955) and O. echigoense Matsuoka 1983 demonstrated that O. echigoense Matsuoka 1983 is a junior synonym of the former. This restudy also confirmed that O. centrocarpum (Deflandre & Cookson) Wall 1967 (= H. centrocarpum Deflandre & Cookson 1955) is morphologically distinct from the Quaternary dinocysts that are widely attributed to this species in the literature. [These Quaternary forms are referred to in this paper as O. centrocarpum (Deflandre & Cookson) sensu Wall 1967.] Viable cysts that are morphologically identical to the Quaternary forms [i.e., O. centrocarpum (Deflandre & Cookson) sensu Wall 1967] have been incubated to produce the motile dinoflagellate P. reticulatum (Claparéde & Lachmann) Bütschli 1885.
We propose that, 1) the latter name should be applied only to large, morphologically distinct dinocysts comparable to those originally described from the Miocene of Australia, and 2) the distinctive Quaternary forms [i.e., O. centrocarpum (Deflandre & Cookson) sensu Wall 1967] should be referred to as the cysts of Protoceratium reticulatum (Claparéde & Lachmann) Bütschli 1885.
Andrew Slyuter
Maize (Zea mays subsp. mays) dominates the record of prehistoric agriculture in the Neotropics. Nonetheless, many significant questions of Zea systematics and evolution persist. Palynology provides a record central to addressing those questions, but determining pollen grain diameter remains a significant methodological issue: diameter is a key characteristic in identification, and diameter seems to be space-time dependent „ the latter phenomenon but little understood. One issue in analyzing diameter is the confounding effect of microscope-slide mounting media. This study provides correction factors to normalize diameter among silicon oil, glycerine jelly, and acrylic resin (du Pont Elvacite), the last coming into increasing use without previous study of its effect on pollen grain size.
B. A. R. Mohr and S. Mao
Dinocyst assemblages from Ocean Drilling Project (ODP) Leg 113, sites 689 and 690, located at Maud Rise, and Leg 114, Site 698 at South Georgia Basin, are of medium diversity with close to 40 taxa. The floras are dominated by Isabelidinium pellucidum and Odontochitina porifera; common species are Batiacasphaera reticulata, Microdinium cassiculum, Leberidocysta sp. A, Nematosphaeropsis sp. and Valensiella reticulata.
The age of these dinocyst-bearing sections has been determined, using paleomagnetics and biostratigraphy, as early Maastrichtian (Chron 32N), correlative to the uppermost part of the B. coronum to the lower part of the B. magnum nannofossil zones. Comparison with equally well-dated Kerguelen Plateau palynofloras indicates an age equivalent to the dinoflagellate Zone C2, and perhaps also Zone D of Mao and Mohr (1992). The precise age model for these dinocyst floras allows better calibration of other Antarctic shallow marine sections from the James Ross Basin.
Decreasing species diversity and increasing endemism of these floras can be used to reconstruct environmental conditions. Decreasing diversity is interpreted as response to cooling of the Antarctic water masses, probably caused by the onset of a distinct proto-circum-Antarctic current during the latest Campanian and early Maastrichtian.
Svein B. Manum
AND
Tor Skjelbred
Decahedrella martinheadii gen. et sp. nov. is a marine palynomorph consisting of ribbon-like bars outlining two quadrangles each encircled by four pentagons forming a spheroidal network to which an internal sac is loosely connected. It is demonstrated mathematically that the observed organization of quadrangles and pentagons is the only possible given the total number of ten. The taxon has been recorded amongst Miocene dinocysts from eight deep sea coreholes (DSDP/ODP) in the northern Atlantic Ocean, sometimes with high relative frequencies. A dinoflagellate affinity could not be demonstrated.
Valenti Rull
Palynological evidence currently used to determine the global eustatic cycles of Haq et al. (1987) requires the existence of sediments from both continental and marine environments. The present work is a contribution to sequence analysis using sediments of continental nature. The boundaries of palynological zones help to locate and date sequence boundaries (SB) and maximum flooding surfaces (MFS); the SB is characterized by hiatuses and/or sudden floral changes (type 1 SB) and barren intervals with oxidized kerogen (type 2 SB), while the MFS may have a few brackish or marine water representatives. When marine fossils are absent, only paleovegetational criteria can be used. In this case, multivariate methods are used to find the most reliable pollen associations. Among them, the coastal and the more inshore associations are selected to compute an index that estimates the position of the tidal limit (TLI). The lateral movements of this tidal limit are recorded and correlated with corresponding sea level fluctuations, thus inferring the SB and MFS from paleovegetational data. The application of these methodologies to two wells from the Maracaibo Basin (western Venezuela) allowed determination of Maastrichtian to Eocene 3rd order cycles from the supercycle sets Upper Zuni A and Tejas A, as well as reconstruction of the local paleogeography of the coastal area.
Rafaella Bucefalo Palliani and James B. Riding
Palynological studies of the Lower Toarcian Pozzale section of central Italy (Tethyan Realm, Mediterranean province) have revealed significant differences between palynomorph assemblages from the Boreal and Tethyan realms and marked similarities between the two bioprovinces of the Tethyan Realm (Mediterranean and Sub-Mediterranean). The Pozzale dinoflagellate cyst assemblages differ from coeval north European assemblages because of the earlier first occurrence of dinoflagellate cysts belonging to the Parvocysta suite, the abundance of the genus Mendicodinium and the absence of Nannoceratopsis. These features have also been recorded in Tethyan localities belonging to the Sub-Mediterranean province (e.g. Portugal) and in transitional areas between the Tethyan and the Boreal domain (e.g. southern France and Hungary). The Pozzale sporomorph assemblages differ from coeval associations from northern Europe, Portugal, northeast Italy and Israel chiefly due to the low relative proportions of the pollen genus Classopollis. This scarcity in central Italy may be a composite effect of the gradual spread of humid conditions in western Europe during the Early Jurassic and/or of the shifting of the paleoenvironment toward distal conditions due to eustatic rises.
Rafaella Bucefalo Palliani
The qualitative and quantitative characteristics of the Toarcian sporomorph assemblages from the Umbria-Marche domain, are consistent with those of the palynological phase VI (late Pliensbachian, Toarcian, earliest Middle Jurassic) as defined by Visscher et al. (1980) in the Germanic realm. The presence of compositional similarities among palynological assemblages from widely separated areas emphasizes the potential of palynology in correlation problems. The Umbria-Marche sporomorph assemblages correspond to an advanced stage of phase VI, where first occurrences of some index taxa, such as Leptolepidites spp., Trilites spp., Ischyosporites spp., Foveosporites spp. are observed, and the genus Callialasporites was represented by only one species, with low relative abundance. By means of qualitative analyses, together with species richness variation trends of older and younger sporomorphs, the Toarcian portion of phase VI in the Umbria-Marche area can be subdivided into two assemblages. The variation trends concerning the relative abundances of bisaccate pollen and pteridophytic spores in the Northern Hemisphere, deduced by comparison with previous data, were related to palaeoclimatic causes.
Ailbhe M. Duane
Two new palynomorph taxa are described, and several existing taxa are discussed from the Upper Jurassic-Lower Cretaceous Byers Group of Livingston and Snow islands, South Shetland Islands, Antarctic Peninsula. Oligosphaeridium byersense sp. nov., a dinoflagellate cyst species, is found in the Valanginian interval of the Byers Group. Globorotundata acrita gen. et sp. nov., a palynomorph of unknown affinity, is a reliable indicator of dysaerobia-anaerobia and/or shallow marine paleoceanographic conditions, when present in moderate to high numbers. This paper includes the first description and discussion of focused ion beam milling preparation of palynological material.
Robert A. Gastaldo and James R. Staub
An actualistic investigation has been conducted on palynofacies recovered from a limited sample set of water column and grab samples in freshwater fluvial, brackish water fluvial, and estuary mouth (kuala) environments of the Rajang River and delta, Sarawak, East Malaysia. Palynofacies are overwhelmingly dominated by Unstructured Organic Matter (OM), with varying amounts of Structured OM, Palynological OM, and an insignificant amount of Indeterminate OM (black opaques). Non-parametric statistical analyses (Chi-Square and Mann-Whitney rank sum) were conducted to determine if different physical processes operating in the delta (tidal range, time of sample collection, water chemistry, and depositional setting) affected assemblage composition. Palynofacies assemblages were evaluated using UPGA clustering techniques to determine if distributional patterns existed in the study area.
No statistical relationship was found between the OM particle category and sediment-grain size within the delta. In general, assemblages from water-column samples recovered from freshwater sites have significantly higher proportion of Unstructured OM than do assemblages from saltwater influenced sites. A similar distribution is seen in grab samples, except that river channels active during the dry season possess the same palynofacies assemblages at the sediment-water interface and differ from abandoned, tidally flushed channels. The abandoned channels have higher proportions of Structured OM both in the water column and at the sediment-water interface than do OM assemblages from freshwater collection sites. There is no 1:1 relationship between the OM assemblages found in the water column, at the sediment-water interface, and sediment recovered from the subsurface (using vibracores) from the same generalized collection area. Early diagenetic alteration in sites influenced by marine waters alters the character of the acid-resistant organic constituents with the production of Black Opaque Indeterminates, resulting in a different acid-resistant organic assemblage.
Javier Helenes and Joyce Lucas-Clark
Species assigned to the widely known genus Gonyaulacysta are typically bicavate with an apical horn, parasutural crests, and a precingular archeopyle. Closely related genera are currently distinguished by variations in the degree of cavation, and shape and size of the parasutural crests. Based on details of morphology and paratabulation, three morphologic groups can be distinguished within species now assigned to Gonyaulacysta, and they are here assigned to three genera:
Gonyaulacysta emend., distinguished by well-developed apical horn and cavation, elliptical cingular cross-section, and a paratabulation pattern including the contacts 1u/1i, A/1i, ai/II, and the presence of accessory K intercalary paraplates. Forms included in this genus as emended here have been described only from Jurassic rocks.
Stanfordella gen. nov., distinguished by weakly developed apical horn and cavation, circular cingular cross-section, and a paratabulation pattern including the contacts 1u/1i, 1u/6, au/Iu, and absence of accessory K intercalary paraplates. Forms included in this new genus have been described from Tithonian to Albian rocks.
Wrevittia gen. nov., distinguished by well-developed apical horn, weakly developed cavation, circular cingular cross-section, and paratabulation pattern including the contacts A/ai, 1u/ai, au/Iu, and variable presence or absence of accessory K intercalary paraplates. Forms included in this new genus have been described from Berriasian to Cenomanian rocks. The paratabulation pattern of this genus is commonly found in Tertiary forms, and in the living species Gonyaulax spinifera.
The separation of these three genera points out the morphological similarities and differences between the species treated here, and should also help to biostratigraphically resolve Middle Jurassic to Cretaceous sedimentary sequences.
New taxa include: Stanfordella granulosa gen. nov., sp. nov., S. exsanguia comb. nov., S. fastigiata comb. nov.; S. ordocava comb. nov., Wrevittia gen. nov., W. helicoidea comb. nov., W. cassidata comb. nov., W.? diutina comb. nov., and W.? perforobtusa comb nov.
Rafaella Bucefalo Palliani and James B. Riding
Two species of dinoflagellate cysts, Umbriadinium mediterraneense gen. et sp. nov. and Valvaeodinium hirsutum sp. nov. occur in the Lower Jurassic (lower Toarcian) of the Tethyan Realm. Umbriadinium mediterraneense exhibits a suessiacean paratabulation with eight to nine paraplate series and a disintegration type combination archeopyle. Valvaeodinium hirsutum is a species characterised by small size and ornamented by numerous non-tabular spines arising from the autophragm. The two new species are confined to the Tethyan Realm, where they are reliable biomarkers for the lower Toarcian.
G. E. Rouse and P. S. Mustard
Mustard and Rouse (1994) effectively published the names of eleven new species and one new genus (Varisulcosporites) of Paleogene fungal spores and two new species of Intratriporopollenites. Unaware of changes in the last editions of the International Code of Botanical Nomenclature, they did not follow proper procedure, and did not publish these names in a valid manner, which consequently were nomina nuda.
R. John Picard and J. M. Selkirk
We describe a peat core sampler which uses one cutting head on as many coring tubes as necessary. We also offer practical suggestions to overcome difficulties of labeling sample tubes when working in wet conditions.
Valenti Rull
The palynological analysis of an outcrop from the northern Venezuelan Andean flank shows that the palynologically-derived Oligo/Miocene chronostratigraphy and paleoenvironmental succession is consistent with previous sedimentological studies for the section. The sequence studied was deposited in alternating coastal and alluvial plain environments, with a variable influence of brackish water. Brackish fern swamps and freshwater alluvial plain forest swamps were dominant, depending on the proximity of the marine shoreline. Paleosalinity was estimated by a ratio between freshwater algae and marine forms . However, freshwater algae Pediastrum and Botryococcus may also tolerate low ranges of salinity, and this factor must be taken into account in future studies. A Late Oligocene phase of increased tectonic activity, possibly related to the Andean uplift, is suggested. In agreement with previous surveys, a striking evolutionary change was observed in Eocene and post-Eocene lower coastal plant communities. The Oligo/Miocene palynoflora of the region studied is similar to that of the rest of Venezuela.
Mirta Quattrocchio, Wolfgang Volkheimer and Cecilia del Papa
An integrated biochronological and physical stratigraphic approach was used as the basis to determine the stratigraphic position of the "Faja Gris" of the Mealla Formation at Garabatal Creek, NW Argentina. The relative dryness that influenced the sediments and the palynological assemblage of the "Faja Gris" can be correlated with an episode of relative low sea level in the marine Atlantic basins during the Riochican Land Mammal Age (Middle to Late Paleocene).
The comparison of fossil genera with extant taxa permits recognition of several paleocommunities, namely marsh, lacustrine, fluvial, montane forest, cloudy forest, transitional forest and steppe. The megaspore species Grapnelispora evansii has its youngest and northernmost occurrence in the Mealla Formation.
Based on the palynological and sedimentological results, the analyzed profile would be located on the calcareous pelite plain environment defined by Gomez Omil et al. (1989) for the "Faja Gris."