Bisaccate Pollen Research Articles

THE RED HILLS MINE PALYNOFLORA: A DIVERSE SWAMP ASSEMBLAGE FROM THE LATE PALEOCENE OF MISSISSIPPI, U.S.A.

Lignites from the Red Hills Mine in Mississippi, U.S.A. contain pollen and spores derived from paratropical swamp vegetation on the U.S. Gulf Coast during the Late Paleocene. Most previous studies of the Gulf Coast sporomorph record have been limited to a restricted taxonomic group, or merely those taxa that are relevant to biostratigraphy, meaning that the true sporomorph diversity may be higher than previously appreciated. Eight samples were collected for palynological analysis from the Red Hills Lignite Mine in Ackerman, Mississippi. All the taxa observed during counting (a minimum of 300 grains per sample) were included in the sample count. Rarefaction, relative abundance distributions, and non-metric multidimensional scaling were used to analyze floral composition, richness, and evenness. The lignite samples are heterogeneous in terms of composition and relative abundances, indicating patchiness in the swamp communities. Clay horizons representing temporary marine incursions contain significantly higher proportions of bisaccate pollen, which may have originated a considerable distance inland from the swamps. These samples therefore represent a much larger source area (regional to sub-continental), compared to the local signal contained in the lignite samples. Richness in the Red Hills Mine assemblage is higher than has previously been recorded for the Late Paleocene of the eastern Gulf Coast. This, combined with the recognition of 23 previously undescribed taxa, suggests that a detailed reappraisal of the Gulf Coast Paleocene sporomorph record is needed to improve understanding of the evolution of the North American vegetation type.

Description and differentiation of Pseudolarix amabilis pollen Palaeoecological implications and new identification key to fresh bisaccate pollen

The differentiation of Pseudolarix from other bisaccate pollen is considered as a tool to investigate the fossil history of this genus. Using Light Microscope (LM) and Scanning Electron Microscopy (SEM) we performed a descriptive and morphometric analysis of Pseudolarix amabilis (Pinaceae) bisaccate fresh pollen grains. Descriptive differentiation characters from Pinus and from other bisaccates have been established. A morphometric differentiation from pine pollen belonging to Pinus sylvestris type was obtained through a study of twelve living species of Pinus. A new identification key for bisaccate pollen grains of living conifers has been elaborated. Although it is addressed to identification of fresh pollen, the proposed descriptive criteria may also be applicable to well-preserved fossil material. A Pliocene site from N-Italy, rich in Pseudolarix cone scales and needles, was used to test the reliability of the proposed criteria on fossil pollen. We also identified Pseudolarix pollen from the lacustrine sediments from Massif Central (France), about 3 My. We carried out a complementary evaluation of the ecological and climate ranges both of the living species and of the fossil assemblages that included Pseudolarix. This tree was a component of the warm-temperate mixed conifers rainforests of the Cenozoic, a biome yielding, after considerable reduction of floristic diversity, overall conifer decimation, to the modern “mixed mesophytic” and “mixed hardwood” forest types. Although its fossil record reveals a wide distribution in the Northern Hemisphere during the Cenozoic, macrofossils are only scattered. On the other hand, information about the pollen production, aerodynamics and taphonomy of Pseudolarix pollen suggests that this tree is among the properly or moderately over-represented genera in pollen images from its natural habitat. Therefore, its pollen record may add clarifications to palaeoclimate reconstructions of Cenozoic environments.

Dinoflagellate cysts from the Middle Eocene to ?lowermost Oligocene succession in the Kysing research borehole, central Danish basin

Rich and well‐preserved assemblages of organic walled dinoflagellate cysts in 50 samples from a 154 m thick and almost complete, Middle Eocene to ?lowermost Oligocene section from the Kysing Research Borehole in eastern Jylland, Denmark are systematically described. One genus Costacysta gen. nov., and twelve species Chiropteridium eocaenicum sp. nov., Costacysta bucina gen. et sp.nov., Distatodinium pilosum sp. nov., Echinidiniuml lucidum sp.nov., Hapsocysta kysingensis sp.nov., Horologinellal pentagonalis sp.nov., Operculodinium eisenackii sp. nov., Phthanoperidinium cornutum sp. nov., Selenopemphix septum sp. nov., Svalbardella partimtabulata sp. nov., Thalassiphora gracilis sp. nov. and Thalassiphora microperforata sp. nov. are formally described. The genus Hapsocysta is emended, and is considered to be a senior synonym of Piccoladinium. The gradual change of the dinoflagellate cyst assemblages in this section demonstrates that sedimentation was almost continuous during the time span of ca. 12 Ma. The biostratigraphic resolution based on dinoflagellate cyst events is generally finer than the calcareous nannofossil NP biozonation. A comparison with published dinoflagellate cyst data from the Norwegian‐Greenland Sea shows that several important events are mainly synchronous throughout the region, suggesting a general similarity of the water masses. An isolated occurrence of Svalbardella suggests a short cooling event during early Bartonian times. The palynofacies in most of the section is almost purely of pelagic type. A more proximal, mid shelf palynofacies and a distinctive episode of reworking coincide with the Upper Eocene Moesgaard Clay and indicate a brief, but rather large sea level fall during the deposition of this unit. The Eocene/Oligocene boundary is tentatively identified near the base of the Viborg Formation, and approximately coincides with increased reworking of dinoflagellate cysts and a strong increase in bisaccate pollen, indicating more proximal conditions and possibly also a climatic cooling.

Late Permian flora and vegetation changes near the Permian–Triassic boundary in the Landete section of the Alcotas Formation (SE Iberian Ranges, Spain)

On the basis of rich and diverse Thuringian palynomorph samples gathered from successive levels of the Landete section (Alcotas Formation, SE Iberian Ranges), the succession of palynofloras and the vegetation dynamics have been studied in detail with the aid of quantitative analysis. The aim of this study is to elucidate the timing and scenario of the biotic crisis during the latest Permian before the actual Permian–Triassic boundary and to determine the shape of the extinction at the local level. Four successive associations have been recognized through time; the oldest, a Klausipollenites–Lueckisporites association. This was followed by a Klausipollenites–Falcisporites, an Alisporites–Lueckisporites and, finally, a re-establishment of a Klausipollenites–Lueckisporites association. It is worth noting the scarcity or lack of fungal remains which indicates that in this area the “fungal-spike” event cannot be demonstrated. The palynomorph associations are dominated by non-striate bisaccate pollen and verrucate spores in contrast with other palynofloras from Western Europe, North America and continental series in Eurasia. The study indicated the absence of transitional floras and a dieback of diversity that ranges from 35% to 67% depending on the group. Population density of the 27 taxa identified underwent a significant decline (ca. 75% average), indicating that, at least at a local level, the biotic crisis occurred prior to the P/T boundary. Futhermore, the quantitative analysis of the successive palynomorph assemblages allowed us to locally recognize the evolution of vegetation in which competitive exclusion and competitive release events took place.

A reinterpretation of the Wagendrift Quarry, Estcourt, KwaZulu-Natal Province, and its implications for Karoo Basin Paleogeography

The South African Karoo Basin preserves a continental record across the Permian/Triassic Boundary in which both plant and vertebrate fossil assemblages may co-occur. The Upper Permian part of the Beaufort Group, a shallow-water fluvial succession spans this boundary. The Estcourt Formation previously was interpreted to be part of this group representing shallow bay fill, the result of overbank deposition. This interpretation implies that sedimentation occurred along the margins of a large, shallowing basin during the Late Permian. Recent work in a series of outcrops at Wagendrift Dam, near the town of Estcourt, requires a reinterpretation of this setting. Three outcrops consist of eight facies, six of which are characteristic of a submarine turbidite system. Basal-most massively bedded sandstones, interpreted as submarine channel deposits are overlain by millimeter-scale, fining upwards couplets of siltstone to mudstone that are distal turbidite in origin. Millimeter-scale bedding is undisturbed and bioturbation is limited, indicating deposition within a low oxygen zone. Ripple cross laminated and ball-and-pillow sandstones, overlain by a finer, massive siltstone are indicative of more proximal turbidites, which is further supported by the presence of large, localized olistoliths (slump blocks) in which internal bedding is preserved. Millimeter-to-centimeter scale upwards-fining successions of planar to ripple cross laminated beds of coarser (fine sand, coarse silt) sedimentary rocks overlain by finer siltstone represent a continuation of proximal turbidite conditions. Thick, ripple-bedded sandstones cap the section, representing a major change in depositional setting into a turbidite fan channel system. The sedimentological characteristics of this succession suggest that although these rocks are assigned to the Latest Permian Beaufort Group, they are, in fact, part of the Ecca Group. Palynomorphs recovered from the quarry are of Late Permian age and consist of taeniate and non-taeniate bisaccate pollen, and spores. Assignment of the assemblage, based on partial canonical correspondence analysis, places the Wagendrift palynoflora in the lower part of Aitken’s Biozone VI (Volkrust Formation; Wujiapingian). These results indicate that turbidite sedimentation similar to that in the southern and western part of the basin persisted into the Late Permian of KwaZulu-Natal.

Palynostratigraphy, lithostratigraphy and thermal maturity of the Lower Triassic Toad and Grayling, and Montney formations of western Canada, and comparisons with coeval rocks of the Sverdrup Basin, Nunavut

Abstract In western Canada samples obtained from outcrops of the Lower Triassic Toad and Grayling formations and core samples from coeval subsurface sections of the Montney Formation contain well-preserved palynofloras. These are generally dominated by taeniate bisaccate (e.g. Lunatisporites noviaulensis) and polyplicate gymnosperm pollen (e.g. Ephedripites steevesiae). Acanthomorph acritarchs (e.g. Filisphaeridium sp. cf. F. deunffii, Micrhystridium breve, M. setasessitante, Wilsonastrum colonicum) are often common to abundant. In addition, the stratigraphically and environmentally significant alga(?) Chordecystia chalasta occurs. These western Canadian Lower Triassic assemblages correlate with the Griesbachian Chordecystia chalasta–Striatoabieites richteri Assemblage Zone of the Sverdrup Basin, Canadian Arctic Archipelago, Nunavut. The environment of deposition, based on the abundance of pollen and spores and common occurrence of acanthomorph acritarchs, is near-shore marine. At a few horizons in the Montney Formation acritarchs are dominant, and this may indicate deeper water facies. Trace fossils in core and outcrop, lithofacies and sedimentary structures indicate fully marine, proximal offshore to lower and upper shoreface settings. The paleoclimate at the site of plant growth, based on the dominance of taeniate bisaccate pollen and polyplicate pollen, was probably arid. The Lower Triassic samples commonly include reworked Middle and Upper Devonian spores and less common Lower Carboniferous spores, demonstrating that significant erosion of Paleozoic rocks took place in early Triassic time in this area; recognition of such erosional events is relevant to sequence stratigraphic reconstructions. The thermal maturity of the in situ organic matter in the study areas is generally low (close to the threshold or within the oil window). This, along with the abundant amorphous and common exinous material, suggests a potential for the generation of liquid hydrocarbons. At one locality in southeast Yukon within the deformation belt the thermal maturity is high, suggesting some potential for dry gas generation. Reworked material generally has a slightly higher maturity, a fact that should be taken into consideration when assessing other thermal maturity indicators such as vitrinite reflectance.

Absence of major vegetation and palaeoatmospheric pCO 2 changes associated with oceanic anoxic event 1a (Early Aptian, SE France)

The deposition of organic-rich sediments during the late Early Aptian Oceanic Anoxic Event (OAE) 1a has been interpreted to result in a major decrease of palaeoatmospheric CO 2 concentrations, accompanied by significant changes in the terrestrial flora. In order to test this hypothesis, the OAE 1a interval in the Vocontian Basin (SE France) has been studied with a combined approach including stable carbon isotopes, organic geochemistry and palynology. To estimate changes in palaeoatmospheric CO 2 levels across the OAE 1a, the δ 13C composition of presumed algal biomarkers (low molecular weight n-alkanes, steranes) and of bulk carbonate carbon are used. Our results yield estimated Early Aptian carbon dioxide partial pressure ( pCO 2) values three to four times the preindustrial level and only a moderate drop across the black shale event. This moderate drop in pCO 2 is supported by palynological results. The frequency patterns of climate-sensitive sporomorphs (incl. pteridophyte spores, bisaccate pollen and Classopollis spp.) display only minor fluctuations throughout the studied section and indicate relatively stable patterns of terrestrial vegetation during and after formation of the OAE 1a black shale. The occurrence of a characteristic Early Aptian carbon isotope pattern across the OAE 1a interval permits accurate chemostratigraphic correlation with the well-studied Livello Selli interval of the Cismon record (N Italy). The contemporaneous formation of individual black shale layers at both sites indicates that transient episodes of dysoxic–anoxic bottom waters prevailed over large areas in the W Tethys Ocean independent of depositional setting. Comparison of the palynological data from the two locations displays significant differences in the frequency patterns of bisaccate pollen. The contrasting pollen spectra are interpreted to reflect prominent changes in the palaeoceanographic current patterns and/or selective sorting due to sea-level rise rather than latitudinal shifts of the major floral belts.

New Late Carboniferous-Early Permian palynological data from glacial sediments in the Kooli Formation, Republic of Yemen

Other| July 01, 2002 New Late Carboniferous-Early Permian palynological data from glacial sediments in the Kooli Formation, Republic of Yemen Hamed A. El-Nakhal; Hamed A. El-Nakhal Islamic University of Gaza, Department of Environment and Earth Sciences, Gaza, Israel Search for other works by this author on: GSW Google Scholar Michael H. Stephenson; Michael H. Stephenson Search for other works by this author on: GSW Google Scholar Bernard Owens Bernard Owens Search for other works by this author on: GSW Google Scholar Author and Article Information Hamed A. El-Nakhal Islamic University of Gaza, Department of Environment and Earth Sciences, Gaza, Israel Michael H. Stephenson Bernard Owens Publisher: Micropaleontology Press First Online: 03 Mar 2017 Online Issn: 0026-2803 Print Issn: 1937-2795 GeoRef, Copyright 2004, American Geological Institute. Micropaleontology (2002) 48 (3): 222–228. https://doi.org/10.2113/48.3.222 Article history First Online: 03 Mar 2017 Cite View This Citation Add to Citation Manager Share Icon Share Facebook Twitter LinkedIn MailTo Tools Icon Tools Get Permissions Search Site Citation Hamed A. El-Nakhal, Michael H. Stephenson, Bernard Owens; New Late Carboniferous-Early Permian palynological data from glacial sediments in the Kooli Formation, Republic of Yemen. Micropaleontology 2002;; 48 (3): 222–228. doi: https://doi.org/10.2113/48.3.222 Download citation file: Ris (Zotero) Refmanager EasyBib Bookends Mendeley Papers EndNote RefWorks BibTex toolbar search Search Dropdown Menu toolbar search search input Search input auto suggest filter your search All ContentBy SocietyMicropaleontology Search Advanced Search Abstract Sparse assemblages of palynomorphs have been collected from the glacially derived Khalaqah Member of the Kooli Formation in northwest Yemen. The presence of common Leiosphaeridia and Deusilites tentus, indeterminate taeniate bisaccate pollen, and such species as Plicatipollenites malabarensis, Verrucosisporites sp., Brevitriletes cf. B. cornutus, and Cristatisporites cf. C. crassilabratus, suggest an age range from Late Carboniferous to Early Permian. Previous workers have considered that a small variation in wall thickness could be used to separate Deusilites tenuistriatus Gutierrez et al. 1997 from the Early Permian of Brazil and Argentina from Deusilites tentus Hemer and Nygreen 1967. The evidence from the Kooli Formation, of highly variable wall thicknesses within a single population of Deusilites suggests that the two species should not be separated and that D. tenuistriatus is a junior synonym of D. tentus. This content is PDF only. Please click on the PDF icon to access. You do not have access to this content, please speak to your institutional administrator if you feel you should have access.

Palynofacies of marginal marine deposits: the rhaetian of the east margin of the Massif Central (France)

The methodology presented concerns the definition of palynofacies. It develops 3 procedure stages based on multivariate analyses: 1 — define the palynomaceral facies, 2 — define and compare palynomorph facies with palynomaceral facies and 3 — exploit the two precedent categories of facies. The study deals with Rhaetian sedimentary cycles corresponding to the western limit boundary of the southeastern France intracratonic basin. Rhaetian strata are representative of paralic depositional environments, overlying Triassic fluvial deposits. On the palynomaceral sequence, that is revealed by multivariate analyses, the most buoyant particles are the needle-like phytoclasts. Crevasse splays, dewatering, drowned soils and restricted wave-influenced deposit facies yield them. The less buoyant particles are the black massive or polygonal phytoclasts. They were produced by crevasses, deltaic shales, distributary channels, palaeosoils, sheet-floods, shoals and shoreface facies. The bisaccate pollen Ovalipollis and the nonsaccate pollen Circumpolles are associated with needle-like particles. They are linked to deltaic shales, restricted deposits sheet-floods, shoal, shoreface and storm facies. The marine element Dapcodinium is not related to a particular palynomaceral type but could be compared to the lowest buoyant phytoclast. Deltaic plain and back-shoal lagoonal facies favour the concentration of Dapcodinium. The distribution of the small size dinoflagellate cysts ( Dapcodinium) and large size dinoflagellate cysts ( Rhaetogonyaulax) emphasizes the role of the size in the floatation competence. Base level-rises and highs are marked by amalgamated bioclastic deposits, fluvial channel fills, mixed siliciclastic-bioclastic amalgamated shoals, storm deposits or ravinement surfaces. Needle-like particles, Ovalipollis and Circumpolles are associated to these deposits. Base level-falls are represented by crevasse splay deposits, fluvial stream incisions, non-incising fluvial channels, sheet flood and stacked palaeosol facies. Black roundish or equidimensional translucent phytoclasts, Rhaetogonyaulax, short-spine Micrhystridium (acritarch) and smooth-walled spores are associated with these facies. In addition to to the energy factor, the water depth constrains both phytoclast and palynomorph sedimentation.

New Late Carboniferous - Early Permian palynological data from glacial sediments in the Kooli Formation, Republic of Yemen

Sparse assemblages of palynomorphs have been collected from the glacially derived Khalaqah Member of the Kooli Formation in northwest Yemen. The presence of common Leiosphaeridia and Deusilites tentus, indeterminate taeniate bisaccate pollen, and such species as Plicatipollenites malabarensis, Verrucosisporites sp., Brevitriletes cf. B. cornutus, and Cristatisporites cf. C. crassilabratus, suggest an age range from Late Carboniferous to Early Permian. Previous workers have considered that a small variation in wall thickness could be used to separate Deusilites tenuistriatus GUTIÉRREZ et al. 1997 from the Early Permian of Brazil and Argentina from Deusilites tentus Hemer and Nygreen 1967. The evidence from the Kooli Formation, of highly variable wall thicknesses within a single population of Deusilites suggests that the two species should not be separated and that D. tenuistriatus is a junior synonym of D. tentus.

Palynostratigraphy of the numidian flysch of Northern Tunisia (Oligocene‐early Miocene)

Diverse and relatively well preserved palynological assemblages from five outcrop sections sampled in the Numidian Flysch of northern Tunisia are presented and discussed. They provide valuable information for age determination and correlation within the Numidian succession. The dinoflagellate cyst zonation scheme of Wilpshaar et al. (1996) for the Oligocene through earliest Miocene of the central Mediterranean area is successfully applied. The basal portion of the Numidian Flysch, which exhibits a faulted contact with the underlying units, crops out in the El Gassaa and Tabarka sections and is dated as early Early Oligocene (Areosphaeridium diktyoplokum‐Reticulatosphaera actinocoronata Zones of Brinkhuis and Biffi, 1993), thus definitely older than previously inferred on the basis of scarce foraminiferal faunas. The youngest beds analysed in the Cap Serrat section are dated as Aquitanian in age (Membranilarnacia ?picena Zone of Brinkhuis et al., 1992) but, as the topmost portions of the Cap Serrat and Ras El Korane sections comprise palynologically barren sandstones and conglomerates cut by the topographic surface, accurate biostrati‐graphic information concerning the top of the Numidian Flysch is still lacking. Dinoflagellate cyst distribution in the examined sections suggests that the first appearance of Tuberculodinium vancampoae may be used as a confirmatory event for recognition of the Reticulatosphaera actinocoronata Zone of Brinkhuis and Biffi (1993) in the Early Oligocene at low paleolatitudes, whereas the extinction of Wetzeliella gochtii may be used for recognition of the Chiropteridium lobospinosum Zone of Wilpshaar et al. (1996). Furthermore, the first appearance of the trilete spore Magnastriadtes howardii Germeraad, Hopping & Müller 1968 and the abrupt increase of bisaccate pollen prove to be locally important for the delimitation of the Eocene/Oli‐gocene boundary.

古琵琶湖層群甲賀累層（鮮新統）よりＣａｔｈａｙａ（Ｐｉｎａｃｅａｅ）花粉の発見

Cathaya (Pinaceae) pollen was discovered from the Pliocene Koka Formation of the Kobiwako Group, Shiga Prefecture, Japan. The pollen morphology was examined with the light and scanning electron microscopes. The characteristics indicate that the bisaccate pollen is Cathaya. This discovery suggests that further study on the pollen flora of the Plio-Pleistocene Kobiwako Group will clarifythe disappearance process and horizon of Cathaya in the area with relation to the climate change.

Late Lower Jurassic palynomorph assemblage in the Dubrajpur sediments, Birbhum District, West Bengal, India

This is the first palynological study of the Dubrajpur sediments exposed near the village Murgadangal within the Birbhum Coalfield of West Bengal. The grey shales and off-white sandy claystones have yielded characteristic palynomorph assemblages. At the base of the succession, which consist of coaly shales. The genus Densipollenites is prominent along with striate bisaccate pollen (Palynozone I). In the same assemblage, the first occurrence of Kremipollenites indicus, Arcuatipollenites pellucidus and Goubinispora indica, is significant. This suggests the end Permian level for the Barakar coal deposits. Subsequently, genus Callialasporites makes its first occurrence at the transition of Barakar and Dubrajpur formations and attains fair presentation in the up-section (Palynozone II) replacing Densipollenites. Definite occurrence of Callialasporites turbatus/dampieri in the presently investigated Dubrajpur strata along with Foraminisporis tribulosus, Klukisporites sp. suggest late Lower Jurassic age for Dubrajpur Formation, and the non-diversified palynomorph composition evidences shallow deposition for this outcrop section.

Late Triassic plant microfossils from Miers Bluff Formation of Livingston Island, South Shetland Islands, Antarctica

A moderately diverse assemblage of plant microfossils has been recovered from the Johnsons Dock Member of the Miers Bluff Formation, Livingston Island, including spores, pollen, acritarchs, wood fragments and cuticles. Containing a total of c. 45 of miospore taxa, the palynoflora is dominated by non-striate bisaccate pollen, but spores of pteridophytes and pollen of gymnosperms are proportionate in diversity. The palynoflora is similar in composition to those indicative of subzones C + D of the Alisporites Zone of Antarctica, and the upper Craterisporites rotundus Zone and the lower Polycingulatisporites crenulatus Zone of Australia as well as the upper Polycingulatisporites crenulatus Zone and Foveosporites moretonensis Zone of New Zealand, suggesting a Late Triassic (possibly Norian–Rhaetian) age. This determination is supported by the sporadic occurrence of Aratrisporites and Classopollis in the palynoflora as well as by the absence of striate bisaccate grains.

Earliest Triassic (Induan) spores and pollen from the Junggar Basin, Xinjiang, northwestern China

Permian–Triassic boundary strata cropping out in the southern Junggar Basin contain a continuous and varied fossil record, making this fluvio-lacustrine succession a potential candidate for a non-marine boundary stratotype. Abundant, diverse and well preserved miospores are recorded and illustrated from the upper part of the Guodikeng Formation and the basal part of the Jiucaiyuan Formation, comprising 92 species and 48 genera, as well as some acritarchs. Seven new species ( Anapiculatisporites decorus Ouyang et Norris, sp. nov., Baculatisporites uniformis Ouyang et Norris, sp. nov., Kraeuselisporites varius Ouyang et Norris, sp. nov., Lapposisporites echinatus Ouyang et Norris, sp. nov., Klausipollenites angustus Shu et Norris, sp. nov., Alisporites exilis Ouyang et Norris, sp. nov., Pilasporites perreticulatus Ouyang et Norris, sp. nov.) and 8 new combinations are proposed. Pteridophytic spores and gymnospermous pollen are almost equally diverse, comprising 45 species in 20 genera, and 43 species in 25 genera, respectively. Pteridophytes are numerically more important, notably Limatulasporites, Kraeuselisporites, Lundbladispora, Anapiculatisporites and Verrucosisporites, but also prominent are bisaccate pollen of Falcisporites, Klausipollenites and Alisporites. Less abundant taeniate pollen are largely bisaccate. These palynofloras are grouped together as the Lundbladispora– Lunatisporites– Aratrisporites Assemblage, argued to be Early Triassic (early Induan), and comprising both newly evolved Mesozoic taxa (herbaceous and shrubby lycopsids, coniferous trees, pteridosperms) and relict Paleozoic taxa (sphenophyllids, cordaitaleans and possibly Paleozoic lycopods). The lower boundary of the Triassic in the section is redrawn somewhat lower than by previous authors. The transitional nature of the Permian–Triassic palynofloras and of the paleophytoprovinces is discussed; neither indicates a sudden catastrophic event affecting terrestrial floras at the P–T boundary on a global scale. The Early Triassic vegetation appears to have grown under humid sub-tropical conditions in lowland flood plains and marshes dominated by hydrophilous and mesophilous pteridophytes and pteridosperms, but with locally drier upland environments supporting xerophilous and mesophilous conifers and pteridosperms. The Induan vegetation is closely comparable to that of the Angara, especially the Subangara Province, although it contains some elements of the Euramerican Province in association with a few Gondwanan, Cathaysian and cosmopolitan taxa.

Chronology of nappe assemblage in the Pan-African Dahomeyide orogen, West Africa: evidence from 40Sr/39 mineral ages : Attoh K., Dallmeyer R.D. & Affaton P., Precambrian research, 1997, 82/1–2 (153–171)

Permian–Triassic boundary strata cropping out in the southern Junggar Basin contain a continuous and varied fossil record, making this fluvio-lacustrine succession a potential candidate for a non-marine boundary stratotype. Abundant, diverse and well preserved miospores are recorded and illustrated from the upper part of the Guodikeng Formation and the basal part of the Jiucaiyuan Formation, comprising 92 species and 48 genera, as well as some acritarchs. Seven new species (Anapiculatisporites decorus Ouyang et Norris, sp. nov., Baculatisporites uniformis Ouyang et Norris, sp. nov., Kraeuselisporites varius Ouyang et Norris, sp. nov., Lapposisporites echinatus Ouyang et Norris, sp. nov., Klausipollenites angustus Shu et Norris, sp. nov., Alisporites exilis Ouyang et Norris, sp. nov., Pilasporites perreticulatus Ouyang et Norris, sp. nov.) and 8 new combinations are proposed. Pteridophytic spores and gymnospermous pollen are almost equally diverse, comprising 45 species in 20 genera, and 43 species in 25 genera, respectively. Pteridophytes are numerically more important, notably Limatulasporites, Kraeuselisporites, Lundbladispora, Anapiculatisporites and Verrucosisporites, but also prominent are bisaccate pollen of Falcisporites, Klausipollenites and Alisporites. Less abundant taeniate pollen are largely bisaccate. These palynofloras are grouped together as the Lundbladispora–Lunatisporites–Aratrisporites Assemblage, argued to be Early Triassic (early Induan), and comprising both newly evolved Mesozoic taxa (herbaceous and shrubby lycopsids, coniferous trees, pteridosperms) and relict Paleozoic taxa (sphenophyllids, cordaitaleans and possibly Paleozoic lycopods). The lower boundary of the Triassic in the section is redrawn somewhat lower than by previous authors. The transitional nature of the Permian–Triassic palynofloras and of the paleophytoprovinces is discussed; neither indicates a sudden catastrophic event affecting terrestrial floras at the P–T boundary on a global scale. The Early Triassic vegetation appears to have grown under humid sub-tropical conditions in lowland flood plains and marshes dominated by hydrophilous and mesophilous pteridophytes and pteridosperms, but with locally drier upland environments supporting xerophilous and mesophilous conifers and pteridosperms. The Induan vegetation is closely comparable to that of the Angara, especially the Subangara Province, although it contains some elements of the Euramerican Province in association with a few Gondwanan, Cathaysian and cosmopolitan taxa.

A playa deposit of pre-Yellow Sands age (upper Rotliegend/Weissliegend) in the Permian of northeast England

A complexly interbedded thin succession of sandstone, siltstone and mudstone beneath the Permian Yellow Sands Formation (upper Rotliegend/Weissliegend) was cored in a borehole 11 km off the coast of northeast England. The cored strata rest unconformably on fissured Westphalian B mudstone and mainly comprise low-dipping fine- to coarse-grained grey sandstone with unevenly spaced thinner dark-red to grey mudstone beds and laminae. Most of the sandstone beds are moderately to poorly sorted, fine- to very fine-grained subarkoses, with some sublitharenites, and are weakly to strongly cemented by dolomite (predominant), kaolinite and illite; sedimentary structures include subhorizontal plane to wavy lamination, ripple lamination, salt ridges and soft-sediment deformation. The siltstones and mudstones are more uniform in lithology and primary thickness; they contain sandstone-filled desiccation cracks, mudstone saucers and narrow sandstone dykes. Traces of possible former evaporite minerals are concentrated in the sandstones. By comparison with modem desert depositional environments, these strata are interpreted as the deposits of a playa occupying a depression on a stony, deflationary desert surface on a rock pediment or peneplain flanking the ancestral Pennines. The floor of the depression, which probably lay in the capillary fringe just above the contemporary water table, was periodically flooded so as to form a shallow playa lake. Comparable successions beneath the Yellow Sands have not been recorded from surface exposures in northeast England but mudstone beds at this stratigraphical level have been recorded in four other cored offshore boreholes and are presumed to be of similar origin to those described in this study. The stratigraphical position of these deposits suggests that they may be of pre-Yellow Sands age and coeval with or younger than the Basal Permian Breccia. Palynological analysis of mudstone samples from the core reveal the presence of plant material and indeterminate, pyrite-invested, possibly indigenous bisaccate pollen indicative of a vegetated hinterland with deposition occurring within a reducing, possibly sulphide-rich environment.

Toarcian sporomorph assemblages from the Umbria‐Marche basin, central Italy

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.

Distribution of sedimentary organic matter in a mixed carbonate‐siliciclastic platform environment: Oxfordian of the Swiss Jura Mountains

ABSTRACTOutcrop sections from the Swiss Jura, consisting of carbonate‐siliciclastic deposits spanning the Middle‐Late Oxfordian boundary, provide a palaeogeographical cross‐section ranging from coastal to shallow platform and intra‐platform basin environments. Using a sedimentological and a 3rd order sequence stratigraphic framework based on those sections, the distribution of sedimentary organic matter (palynofacies) has been spatially studied in relation to sequence stratigraphy.The main factors influencing the spatial variations of sedimentary organic matter are the proximity of land, organic productivity, level of biodegradation and hydrodynamic conditions of the palaeoenvironment. These factors determine the distribution of the land‐derived, relatively allochthonous organic constituents (phytoclasts, pollen and spores), and marine, relatively autochthonous constituents (phytoplankton and foraminifera linings).Five main palynofacies parameters appear as good indicators of proximal‐distal trends: the relative proportion of total phytoclasts; the proportion of fresh, translucent fragments among these phytoclasts; the ratio of marine to continental palynomorphs; and the relative amount and species diversity of dinoflagellate cysts. In lowstand deposits, high‐energy hydrodynamic conditions may affect these trends on the shallow platform, where storms tend to increase the proportion of the marine organic fraction landwards. These five palynofacies parameters are largely related to water depth. Therefore, when compared with the established 3rd order sequence stratigraphic framework, their stratigraphic variations indicate relative sea‐level changes or, alternatively, proximality changes. Parameters indicative of more distal conditions increase in the transgressive and early highstand, and decrease in the late highstand. The opposite occurs for parameters indicative of more proximal conditions. Foraminifera linings seem to be particularly concentrated near the shelf edge and on the slope. Finally, bisaccate pollen may display cyclicity associated with alternating humid and dry periods. This palaeoclimatic signature may be related to orbital cyclicity.

Intraspecific Variation of Taeniate Bisaccate Pollen Within Permian Glossopterid Sporangia, from the Prince Charles Mountains, Antarctica

Permineralized sporangia from Late Permian sediments of the Amery Group in the Prince Charles Mountains, East Antarctica, are assigned to Arberiella sp. cf. A. africana Pant and Nautiyal. These sporangia contain between 2000 and 3000 taeniate, saccate pollen grains that are predominantly haploxylonoid bisaccate and referable to the palynotaxon Protohaploxypinus limpidus (Balme and Hennelly) Balme and Playford. However, the sporangia also contain greater than 4% of diploxylonoid bisaccate forms comparable to Striatopodocarpidites cancellatus (Balme and Hennelly) Hart 1963, together with sporadic monosaccate and trisaccate grains that, if found dispersed, would be assigned to several different pollen form genera. Morphometric analysis of in situ bisaccate pollen grains and taeniate bisaccate pollen in the dispersed palynoflora indicates that in situ grains occupy only the smaller end of the total size range. The tendency for in situ grains to cluster into two different size groups may reflect differential predispersal expansion of the corpus. The in situ pollen grains are variable in most qualitative and quantitative features used for taxonomic discrimination of dispersed taeniate bisaccate pollen, and this may lead to unreliable estimates of Late Permian floristic diversity if an overly restrictive species delimitation scheme is used.