Palynological Biostratigraphy Research Articles

Vegetation changes and climate shift during the latest Ladinian to the early Carnian: Palynological evidence from the Yanchang Formation, Ordos Basin, China

The Middle–Late Triassic climates have attracted the attention of paleontological and geological scientists for the Carnian pluvial event in the early Late Triassic. The event is well-documented in the pelagic and epi-continental marine deposits of the Tethys, Gondwana, and Laurasia. However, inland terrestrial deposits are less frequently depicted, with high-resolution palynological biostratigraphy constraints. In this study, we report the palynological records from the YC8-1 and YC7-3 sub-members of the Yunmeng profile in the Ordos Basin, China, where the YC7-3 was dated at 236.0–234.1 Ma. Two palynological assemblages were recognized and named the Lundbladispora watangensis–Taeniaesporites combinatus assemblage and Lundbladispora communis–Discisporites granulus assemblage for the YC8-1 and YC7-3 sub-members, respectively. Their ages were determined to be the latest Ladinian and early Carnian, respectively, for their stratigraphic correlations with the global boundary stratotype section and point (GSSP) of the base of Carnian in Europe and additional co-occurring floras with condonts in the Upper Triassic of South China. The coexistence of Cyathidites minor (Couper, 1953), Dictyophyllidites harrisii (Couper, 1958), Apiculatisporis bulliensis (Helby ex De Jersey, 1972), Aratrisporites xiangxiensis (Li and Shang, 2011), Piceaepollenites omoriciformis (Bolkh.) (Xu and Zhang, 1984), Podocarpidites ornatus (Pocock, 1962), Discisporites granulus (Zhang, 1984), and Classopollis (Pflug, 1953) is equivalent to the Carnian palynostratigraphic criterion reported in the North China palynofloristic realm. Vegetational changes, especially those occurring at the boundary between Ladinian and Carnian, account for approximately 70% of ferns and over 30% of gymnosperms lost. These were discovered and attributed to the strong seasonal arid climate, indicated by the emergence of Cheirolepidiaceae and Pinuspollenites. We thus know that the climate during the latest Ladinian and early Carnian was “hot house” with seasonal aridity. In addition, three strong monsoonal pluvial pulses were signaled by the humidity index of lowland plants. The present study will enable a better understanding the Carnian pluvial event in the Late Triassic inland basin.

Exploring the role of High Arctic Large Igneous Province volcanism on Early Cretaceous Arctic forests

The Hauterivian–Aptian Isachsen Formation at Glacier Fiord, Axel Heiberg Island, in the Sverdrup Basin of the Canadian Arctic Archipelago was deposited contemporaneous with initiation of the High Arctic Large Igneous Province (HALIP). New palynological biostratigraphy and paleoenvironmental reconstruction, in coordination with the emerging geochronology of HALIP igneous rocks, permits exploration of the effects of volcanism on Arctic vegetation during the Early Cretaceous. Four informal terrestrial palynofloral zones are defined and used to reconstruct vegetation change over the Isachsen Formation's ca. 17 million year history and explore the role of the HALIP in these changes. Climate warming during the Hauterivian promoted expansion of a hinterland community dominated by members of the Pinaceae. By the middle Barremian, this community was replaced by mixed heathland and mire, represented by up to 70% fern spores in the uppermost Paterson Island Member, that may be, in part, in response to environmental disturbance associated with volcanic flows of the HALIP. Above the fern spore spike, dinoflagellate cyst assemblages suggest an early Aptian age and a marine setting for mudstones of the Rondon Member in which Ocean Anoxic Event 1a is recorded. An interval of floral instability is recorded in the overlying Walker Island Member, characterized by fluctuations in Pinaceae and Cupressaceae pollen and fern spores, possibly as a result of post-OAE 1a temperature variabilty and landscape disturbance associated with lava flows of the HALIP that were repeatedly extruded onto the subsiding delta plain during deposition of the member.

Re-investigating Miocene age control and paleoenvironmental reconstructions in western Amazonia (northwestern Solimões Basin, Brazil)

The modern Amazonian rainforest has a great fascination and global significance, but our knowledge of past landscape changes is still limited due to sparse data and the lack of radiometric age constrains. Precise dating in records older than the late Pleistocene are difficult to obtain and often regionally confined, therefore biostratigraphic correlations are used to estimate depositional ages across sedimentary basins. Aiming for a better understanding of the Neogene changes in western Brazil, we studied palynology and ostracod assemblages from the Solimões Formation, a key site for paleoenvironmental models to discuss the biotic changes in Amazonia. Further, we compare the biostratigraphic information of both groups with radiometric maximum deposition ages constrained by U/Pb measurements on detrital zircon grains.Down to the depth of ~95 m, zircon populations show a maximum deposition age of 11.42 ± 0.66 Ma documenting Tortonian (late Miocene) or younger ages for the top of the Solimões Formation. Palynological biostratigraphy show the Psilatricolporites caribbiensis zone (latest Miocene–Pliocene) down to a depth of 181.8 m, where the Grimsdalea magnaclavata zone suggests a late middle Miocene to early late Miocene age. In comparison, ostracod biostratigraphy indicates the Cyprideis cyrtoma zone (late Miocene) down to 176.0 m and the Cyprideis minipunctata (late middle to late Miocene) for the bottom of the section. Thus, both biostratigraphic concepts suggest ages close to the maximum ages indicated by the detrital zircons. This comparison of the biozonations with U/Pb maximum deposition ages represents the first independent calibration of these widely used methods for age determination in the Solimões Basin.Palynological and ostracod data illustrate dynamic environments varying from fluvial settings with wetland forests and swamps to lakes and/or abandoned channels with temporary slightly saline conditions. Instead of a slow evolution of Neogene Amazonian environments, our results show migrating rivers and waterbodies surrounded by rainforest during the period recorded by the base and top of the studied core material, separated by a phase of more extensive lakes and swamps (core depth 90–120 m). Indicators for slightly elevated salinity are found until the topmost sample and thus persisted during the late Miocene.This highlights the importance of new age control to improve the regional biostratigraphic timescale and reconstructed environmental changes.

Early Oligocene (Rupelian) Dinoflagellate Cysts and Calcareous Nannofossils from Lumpy Clay Member of Maniyara Fort Formation, Kutch, Gujarat, India

The Palaeogene succession of Kutch, Gujarat exhibits huge shallow marine carbonate deposits of Middle Eocene and Oligocene ages. These deposits were mainly dated on the basis of larger benthic foraminifers. The paucity of foraminifers in the intermittent units of the succession resulted in discrepancy in precise dating of these strata. Lumpy Clay Member of Maniyara Fort Formation is one such example. This is considered as unfossiliferous in terms of foraminifers and was dated on the basis of foraminiferal assemblages of underlying Basal and overlying Coral Limestone members. In the present study, palynological biostratigraphy is proposed for the Lumpy Clay Member exposed at Bermoti Village, in Kutch. On the basis of age-diagnostic calcareous nannofossil and dinoflagellate cyst assemblages, the studied succession has been dated as Middle Rupelian (~31 Ma). The palynological data suggests a shallow marine neritic depositional setting, occasionally swept by open oceanic water.

Palynostratigraphic and U-Pb CA-IDTIMS isotopic dating of the upper Orallo Formation, northern Surat Basin, Queensland

The Jurassic–Cretaceous transition in the Surat Basin, Queensland, has not been previously subjected to detailed palynological study and biostratigraphic assessment. The associated lithostratigraphic succession, that is represented by the upper Westbourne Formation, the unconformably overlying Gubberamunda Sandstone, and the succeeding Orallo Formation and Mooga Sandstone, represents the most complete record of deposition for the interval in Queensland. Several important aquifers and aquitards occur in this succession, and a refined palynological biostratigraphy may assist in providing more accurate correlations and improved conceptual models for its deposition and spatial variability. Preliminary results of the investigation suggest that the existing pan-Australian zonal scheme and the informal alphanumeric scheme widely applied in eastern Australia can be modified to more accurately reflect the stratigraphic distribution of palynomorph species present in, and the overall palynofloral composition of, these uppermost Jurassic–lowermost Cretaceous rocks, not only in the Surat Basin but also, by extrapolation, their equivalents in other eastern Australian basins. This will thus facilitate more accurate intra- and inter-basinal correlations. In the Orallo Formation material studied to date, zone-index fossils—though present—have proved to be scarce, but this is relative to the extreme richness and the diversity of taxa in the assemblages, the composition of which appears to differ significantly from that described in the literature, and reflects the temperate climate in the environment of deposition. On an introductory basis—as the study is in its early stages—a number of new species have been provisionally identified, and several existing species are seemingly in need of taxonomic emendation.

Foraminiferal and palynological biostratigraphy and biofacies from a Santonian–Campanian submarine fan system in the Vøring Basin (offshore Norway)

Foraminiferal assemblages from a Santonian–Campanian submarine fan system in the northwestern Vøring Basin, offshore Norway were investigated with the primary objectives to document the stratigraphic ranges of foraminiferal taxa calibrated with dinoflagellate cysts, and to interpret foraminiferal biofacies of different fan sub-environments previously proposed based on the analysis of ichnofossils. The assemblages are composed of deep-water agglutinated foraminifera (DWAF) without carbonate-cemented taxa. DWAF taxa of high biostratigraphic value are absent, but the complete agglutinated nature of the assemblages and the presence of Gerochammina stanislawi and Rectogerochammina eugubina are similar to those of the lower Campanian Fenestrella bellii Zone of the Norwegian Sea. More reliable dating was provided by palynology, and the age of the interval is estimated to be Santonian to Campanian.The inner to middle fan assemblages contain small numbers of specimens, and consequently the species diversity and relative abundance of morphogroups are inconsistent. Deep infaunal forms may be more common in this sub-environment, but because the abundance is low, this observation should be treated carefully. In contrast, the abundance and diversity of the assemblages of the overbank, fringe and basin plain sub-environments are fairly high. Their morphogroup composition is also similar and comparable to each other when the assemblage size is large. The assemblage from the interval with suggested hydrothermal activity is similar to those from outside the channel sub-environment. The presence of bottom water currents, possibly in the form of a western boundary current, in the basin is suggested based on the abundant occurrence of tubular forms in the overbank, fringe, and basin plain sub-environments.

Early Triassic conodont–palynological biostratigraphy of the Meishan D Section in Changxing, Zhejiang Province, South China

The Lower Triassic, consisting of the Yinkeng Fm., Helongshan Fm. and the lower part of the Nanlinghu Fm., is well developed at the Meishan D Section of Changxing County, Zhejiang Province, South China. Based on detailed study of the conodont biostratigraphy from the interval of the Permian–Triassic boundary and the Lower Triassic in the Meishan D Section, 8 conodont zones are recognized in ascending order as follows: the Neogondolella changxingensis yini– Hindeodus praeparvus Zone (beds 24a–24e, top of the Changxing Fm.), the Neogondolella meishanensis meishanensis– Hindeodus eurypyge Zone (beds 25–27b, base of the Yinkeng Fm.), the Hindeodus parvus Zone (beds 27c–27d, first conodont zone of Triassic, the global index for the base of Triassic), the Isarcicella staeschei Zone (beds 28–29a, lower part of the Yinkeng Fm), I. isarcica Zone (beds 29b–51, lower part of the Yinkeng Fm.), the Neogondolella tulongensis– N planata Zone (beds 52–72, from upper part of the Yinkeng Fm. to lower part of the Helongshan Fm.), the Neospathodus kummeli Zone (beds 73–92, middle part of the Helongshan Fm.), and the Neospathodus cristagalli– N dieneri Zone (beds 93–111, from upper part of the Helongshan Fm. to the base of the Nanlinghu Fm.). At the Meishan D Section, the palynological biostratigraphy is also studied herein. The palynological assemblage of Lundbladispora– Taeniaesporites– Equisetosporites is found in the intervals which contain the conodont Isarcicella isarcica Zone and the lower part of the Neogondolella tulongensis– N. planata Zone.

Biodiversity changes in Cretaceous palynofloras of eastern Asia and western North America

Palynology has great potential for providing comparative data and interpretations about changes in biodiversity during the Cretaceous Period. This is especially true for both eastern Asia and western North America because of strong floristic similarities that existed between these regions during Cretaceous time. Also, because palynomorphs of terrestrial origin can be deposited in offshore as well as terrestrial environments, significant potential exists for marine-to-continental palynostratigraphic correlations in both regions. Palynological biostratigraphy can improve the geologic dating of changes in biodiversity. During the Early Cretaceous, eastern Asia and western North America lay within the Cerebropollenites palynofloral province, a circumpolar phytogeographic zone characterized by distinctive palynological assemblages. During most of the Late Cretaceous, these regions lay within the palynofloristically unique Aquilapollenites Province, which was more restricted geographically than the Cerebropollenites Province. The most important development during Cretaceous time that is reflected in palynological assemblages was the rise of the angiosperms as the numerically and ecologically dominant forms of vegetation. The most striking short-term palynofloral event in the two regions was the sudden disappearance of species of Aquilapollenites and associated genera at the Cretaceous–Tertiary (K/T) boundary. Both of these occurrences produced major changes in biodiversity in the terrestrial realm. Geologic research in International Geological Correlation Program Project 434 can benefit from applications of palynostratigraphy. Palynologic research within Project 434 could include development of a comprehensive palynostratigraphic zonation for the Cretaceous, the definition of regional palynostratigraphic datums, and investigation of the record of floral change at the K/T boundary.

Chronology of Devonian to early Carboniferous rifting and igneous activity in southern Magdalen Basin based on U-Pb (zircon) dating

Fifteen U–Pb (zircon) radiometric age determinations have been made on igneous rocks of Middle Devonian to Early Carboniferous age from the southern margin of the Magdalen basin in Cape Breton Island and northern mainland Nova Scotia. Volcanic rocks interbed with early rift-basin sedimentary rocks with some palynological biostratigraphy; dated intrusive rocks cut these sedimentary units. Our biostratigraphically constrained ages are in close agreement with the current Devonian time scale. Combined with previously published data, the age determinations show that igneous activity occurred in four pulses: Middle Devonian (390–385 Ma), early Late Devonian (375–370 Ma), latest Devonian to early Tournaisian (365–354 Ma), and late Tournaisian to early Visean (ca. 339 Ma). Middle Devonian (385–389 Ma) volcanic rocks are confined to the Guysborough Group. The Fisset Brook Formation (basalt and minor rhyolite) in the type area and elsewhere in Cape Breton Island and northern mainland Nova Scotia is Late Devonian (ca. 373 Ma), whereas the biostratigraphically distinct succession at Lowland Cove is younger (365 Ma). These Late Devonian rocks are synchronous with plutonism in the Cape Breton Highlands and the Meguma terrane. In the Cobequid Highlands, rhyolite of the Fountain Lake Group was synchronous with Horton Group deposition and with widespread granite plutons (362–358 Ma) emplaced during shear on the Cobequid fault zone. The overlying Diamond Brook Formation basalts are slightly younger (355 Ma). Late Tournaisian – early Visean mafic intrusions and minor basalt occur along the Cobequid – Chedabucto fault zone and in a belt from southern New Brunswick through Prince Edward Island to southwestern Cape Breton Island.

Datation and palaeoenvironmental interpretation by microplankton and miospore assemblages of the Razzak Oil Field sediments, Western Desert, Egypt

Samples from the Razzak Oil Field were analyzed for palynological biostratigraphy in order to make inferences about palaeogeography and palaeoclimate. The oldest sediments cored and dated from the Razzak-1 well are Aptian in age. Palynomorph recovery was sparse from the Razzak-3 and 12 wells except at depth 5712 ft from the Bahariya Formation. Analysis of the dinoflagellate cyst and miospore assemblages from the Razzak-16 well has shown that the Bahariya Formation is of late Albian to earliest Cenomanian in age. Evidence is presented from the Alam El Bueib Member for a phase of aridity which began in Aptian times. The change from generally dry to humid climates during the Cenomanian is thought to have been linked to a rising sea level. The highest concentrations of marine microfossils (dinocysts and microforaminiferal test linings) at depth 6115 ft indicate that marine conditions are reported near upwelling currents in shallow water or in waters of raised salinity. The neighbouring landmass had less influence at the site of deposition. Data from the Razzak-16 well at a depth of 6110 ft indicates that sporomorphs outnumber the marine palynomorphs. This implies that there was a copious run-off from the neighbouring landmass which reached the site of deposition. Relatively deep marine conditions are postulated for the Cenomanian succession at the site of the Razzak-12 well at a depth of 5712 ft. Les analyses palynologiques dans les prélèvements effectués dans le Razzah Oil Field (Egypte, Désert occidental) fournissent des renseignements sur la paléogéographie et le climat. Les plus anciens sédiments forés dans le puits Razzak-1 sont d'âge aptien. Les puits Razzak-3 et 12 ont fournis peu de palynomorphes sauf à la profondeur de 5712 pieds dans la Formation Baharya. Les assemblages de dinokystes et de spores et grains de pollen du puits Razzak-16 permettent de dater la Formation Bahariya de l'Albien terminal au Cénomanien ancien. Les analyses montrent dans le Membre Alam El Bueib l'existence d'une phase aride qui débute durant l'Aptien. Le climat généralement aride évolue vers l'humidité pendant le Cénomanien probablement en liaison avec une hausse du niveau de la mer. Les plus fortes concentrations de microfossiles marins (dinokystes et basales de foraminifères) à la profondeur de 6115 pieds indiquent des conditions marins avec des courants d'upwelling dans des eaux peu profondes ou à salinité élevée. La proximité de continents avait peu d'influence sur le site de dépôt. Les données du puits Razzak-16 à 6110 pieds de profondeur indiquent que les sporomorphes dominent les palynomorphes marins. Ceci implique qu'une érosion importante du continent alimentait le site de dépôt. Le puits Razzak-12 à 5712 pieds de profondeur indique un environnement marin relativement profond pendant le Cénomanien.

The Quaternary origins of the modern British mammal fauna

The origins of the modern British mammal fauna as a recognizable assemblage are traceable through preceding temperate woodland phases at least as far back as the early part of the Middle Pleistocene. Earlier Quaternary mammal assemblages have more in common with those of the Pliocene than those of the Middle Pleistocene, but evidence for gaps in the British Early Pleistocene sequence precludes inferences concerning the nature of this change in faunal composition. A major difficulty in reconstructing Quaternary faunal histories is in establishing stable correlations between the fragmentary terrestrial sequences from which the fossil record has been recovered and in assembling those sequences into chronological order. Existing reconstructions of Quaternary events in Britain are of hybrid origin, a mix of palynological biostratigraphy based on assumed monocyclic floral successions for a small number of major interglacial stages, with intervening cold stages identified by characteristic glacial or periglacial lithologies and structures. While this framework has served as a useful basis for some Quaternary disciplines, some interpretations of the mammalian evidence do not fit it well. Attention is given here to information derived from fossil mammal assemblages which may be used to help determine the number and sequence of Middle and Late Pleistocene temperate woodland phases with faunas showing close links with that of the Flandrian. While much of this information is not new, it has been largely ignored in the construction of some of the more widely known schemes for Quaternary subdivision. At present five such episodes can be identified and characterized prior to the present interglacial, though further refinement may br possible as work on a more detailed account of key sites arid their palaeontology progresses.

Jurassic-Neocomian Biostratigraphy, North Slope, Alaska: ABSTRACT

The foraminiferal and palynological biostratigraphy of subsurface Jurassic and Neocomian (Early Cretaceous) age strata from the North Slope were investigated to better define biostratigraphic zone boundaries and to help clarify the correlation of the stratigraphic units in the National Petroleum Reserve in Alaska (NPRA). Through use of micropaleontologic data, eight principal biostratigraphic units have been identified. The Neocomian and Jurassic strata have each been subdivided into four main units. The gamma-ray zone (GRZ), or hot zone, sediments include both northern and southern source starved-basin deposits. These deposits range from Barremian to possibly middle Albian age in NPRA. East of NPRA, these Early Cretaceous starved-basin deposits coalesce with Late Cretaceous starved-basin deposits and form a GRZ at least as young as Senonian. Early Cretaceous starved-basin deposits of northern source are recognized by the presence of dispersed, rounded, frosted quartz sand grains. These sand grains, floating in a mudstone matrix, are essentially absent from the starved-basin deposits of southern source. The Lower Cretaceous unconformity occurs within the Hauterivian to Barremian biostratigraphic interval in the Tunalik, Peard, and Inigok wells on the NPRA; it cannot be recognized through microfossil evidence in those particular areas. In most other areas of the North Slope, the unconformity occurs at the base of the Hauterivian to Barremian biostratigraphic interval. This unconformity truncates progressively older strata eastward along the present coastal region and onto the Barrow arch. A mid-Jurassic sandstone unit appears to be of Early to Middle Jurassic rather than Late Jurassic (Oxfordian) age. Lower to Middle Jurassic strata are characterized by southward depositional thinning and distal (starved-basin) deposition in certain areas. The Sag River Sandstone is a time transgressive unit that ranges from Late Triassic in the north and northwestern NPRA to Early Jurassic on the Fish Creek platform to the east. End_of_Article - Last_Page 669------------

Studies in the palynological biostratigraphy of the British Trias. I. Reference sections in west Lancashire and north Somerset

The ranges of a number of distinctive miospores, determined from cored borehole sections in the Lower “Keuper” Marl of west Lancashire and from an outcrop of the Upper “Keuper” Marl and Rhaetic in north Somerset, provide a potential basis for the biostratigraphic subdivision of these deposits and a means of correlating between different British sequences which does not involve reference to the European stage sequence.