Biostratigraphic Changes Research Articles

Multiproxy evidence for environmental stability in the Lesser Caucasus during the Late Pleistocene

The Lesser Caucasus, situated between Asia and Europe, has long been recognised as a key region for the study of human evolution in terms of the timing and routes of dispersal, as well as, ecological adaptations. In particular, scholars have argued whether stable environments persisted in the region throughout the last glaciation, serving as a refugium for temperate biota, likely attracting human settlement and use. Here, we present the results of a multidisciplinary study of Karin Tak Cave, which contains sediments that accumulated between 48,000 and 24,000 cal yr BP. We examined biostratigraphic changes at the site by looking at the composition of fauna, which we hypothesise to be naturally accumulated, in different stratigraphic phases using traditional zooarchaeological approaches combined with collagen fingerprinting (ZooMS, Zooarchaeology by Mass Spectrometry). To gain further insights into regional palaeoenvironmental conditions, we also applied stable carbon and oxygen isotope analyses to faunal tooth enamel. The obtained results suggest that the onset of the last glaciation did not cause dramatic changes in regional environments, indicating that the Lesser Caucasus was a climatically and ecologically stable region despite significant global climatic changes during this period.

BIOSTRATIGRAPHY AND PROTEROGENESIS OF VERNEUILINA FAUNA FROM THE SOUTHERN TETHYS

The Campanian-Ypresian (C-Y) fauna in the Southern Tethys (ST) include rich small benthic foraminifera (SBF) reveals significant biostratigraphic changes during the C-Y transition. A progressive evolutionary trend within the Verneuilina lineage allowed to establish the Campanian V. iraqensis Total Range Zone (TRZ), and three successive zones in the Maastrichtian-Ypresian, namely: the Maastrichtian V. aegyptiaca Interval Range Zone (IRZ), the Paleocene V. laevigata IRZ, and the Ypresian V. luxorensis TRZ, which may correlate with the standard planktonic foraminifera zones: Globotruncana aegyptiaca IRZ to Acarinina pentacamerata PRZ, and span about 23 M.Y. (75-52 Ma). On the other hand, a minor difference in the test morphology and differences in the stratigraphic ranges of the members of the genus Verneuilina are recognized as being of decisive specific value. For that, the Proterogenesis Rule can be applied here on the Late C-Y six species of the genus Verneuilina, and these are: Verneuilina aegyptiaca and V. karreri, V. laevigata and V. luxorensis. Another two species are believed here as new: Verneuilina iraqensis and Verneuilina jordanica. The identified species were recorded from many localities in the ST (Tunisia, Egypt, Jordan, Iraq, Iran, United Arab Emirates, Qatar and Pakistan), and one of them are recorded in Spain, in the Northern Tethys (NT).

Paleozoic Paraná Basin transition from collisional retro-foreland to pericratonic syneclise: Implications on the geodynamic model of Gondwana proto-Andean margin

Providing significant advancements in the knowledge and development of the global plate tectonic theory, the Paraná Basin records a long period of sedimentary accumulation with evidence of substantial climatic and bio-stratigraphic changes throughout most all of the Phanerozoic. Two cycles of sedimentation are identified in the lowermost sequences (Rio Ivaí and Paraná groups), followed by a ~50 Ma gap until the deposition of the early Gondwanic cycle (Itararé Group). The literature suggests that some of those depositional cycles were influenced by episodes of terrane accretion during the amalgamation of the Gondwana Supercontinent. The paleo-topography generated by the Ocloyic orogeny (460-430 Ma) likely resulted in flexural subsidence in the lowermost stratigraphic cycles of the Paraná Basin. In response to dynamic topography, the forebulge probably shifted to a system dominated by long-wavelength propagation developed over a distance of more than 800 km, most likely due to the influence of the subducted oceanic lithosphere of Panthalassa. The presence of Ordovician sources in the pre-Carboniferous sequences supports a provenance of exhumed Famatinian magmatic arc and associated rocks given that Ordovician magmatic activity is not recorded anywhere else in the cratonic regions. Furthermore, important detrital zircon population yielding Cambrian ages, likely derived from Eastern Pampean Range. In additional, the gap between crystallization and depositional ages within the Paraná Basin supports a model that transitions from a collisional retro-foreland basin to a pericratonic syneclise after the deposition of the Paraná Group.

Eocene to Oligocene nannofossils stratigraphy and environmental conditions in Izeh Province, Zagros Basin, East Tethys

Data obtained from the calcareous nannofossils, distributed in the upper part of the Pabdeh Formation (Priabonian–Rupelian) and the lower part of the Asmari Formation (Chattian) in the Bid-Zard section, were used to investigate the Eocene to Oligocene palaeoenvironmental conditions in the southwest of Izeh, southwestern Iran (eastern Tethys). The upper part of the Pabdeh Formation was composed of shale, thin-bedded pelagic limestone and dolostone, which is disconformably overlain by the Asmari Formation. For the first time, 29 species of calcareous nannofossils belonging to 13 genera were identified in the studied section. The calcareous nannofossils in the upper part of the Pabdeh Formation indicate the Isthmolithus recurvus Zone/Sphenolithus pseudoradians Zone (combined zone), Ericsonia subdisticha Zone, Helicosphaera reticulata Zone and Sphenolithus praedistentus Zone, from the Priabonian to the Rupelian. The Sphenolithus ciperoensis Zone of the Chattian was identified in the lower part of the Asmari Formation. Calcareous nannofossil stratigraphy across the upper Eocene–Oligocene interval also reveals a disconformity at the Rupelian/Chattian transition due to a bio-event. Shallowing of the basin and environmental changes in this part of the Tethyan domain could have led to the lithostratigraphic and biostratigraphic changes. In fact, during the late Eocene to late Oligocene, marine phytoplankton was sensitive to climate changes such as decreasing temperature, as well as possibly to a nutrient increase and changes in basin depth.

Environmental variability in response to abrupt climatic change during the Last Glacial–Interglacial Transition (16–8 cal ka BP): evidence from Mainland, Orkney

The Last Glacial–Interglacial Transition (LGIT) is a period of climatic complexity where millennial-scale climatic reorganization led to changes in ecosystems. Alongside millennial-scale changes, centennial-scale climatic events have been observed within records from Greenland and continental Europe. The effects of these abrupt events on landscapes and environments are difficult to discern at present. This, in part, relates to low temporal resolutions attained by many studies and the sensitivity of palaeoenvironmental proxies to abrupt change. We present a high-resolution palynological and charcoal study of Quoyloo Meadow, Orkney and use the Principal Curve statistical method to assist in revealing biostratigraphic change. The LGIT vegetation succession on Orkney is presented as open grassland and Empetrum heath during the Windermere Interstadial and early Holocene, and open grassland with Artemisia during the Loch Lomond Stadial. However, a further three phases of ecological change, characterized by expansions of open ground flora, are dated to 14.05–13.63, 10.94–10.8 and 10.2 cal ka BP. The timing of these changes is constrained by cryptotephra of known age. The paper concludes by comparing Quoyloo Meadow with Crudale Meadow, Orkney, and suggests that both Windermere Interstadial records are incomplete and that fire is an important landscape control during the early Holocene. Supplementary material : All raw data associated with this publication: raw pollen counts, charcoal data, Principal Curve and Rate of Change outputs and the age-model output are available at https://doi.org/10.6084/m9.figshare.c.4725269 Thematic collection: This article is part of the ‘Early Career Research’ available at: https://www.lyellcollection.org/cc/SJG-early-career-research

Diatom responses to long‐term climate and sea‐level rise at a low‐elevation lake in coastal British Columbia, Canada

AbstractDiatom assemblages from Lake Stowell, a low‐elevation lake in coastal British Columbia, were used to assess limnological responses associated with changes in relative sea level (RSL) and climate over the past 14,500 yr. Marine diatom taxa dominated the early record and disappeared abruptly by 14,000 cal yr BP in response to glacio‐isostatic uplift and an ensuing decrease in RSL. A brackish‐freshwater phase from 14,200 to 13,400 cal yr BP was marked by increases in several diatom taxa with tolerance for low‐to‐moderate salinity, after which assemblages became strictly freshwater. Biostratigraphic changes in both diatom and chironomid assemblages from Lake Stowell occurred more or less simultaneously throughout the record in response to long‐term changes in climate forcings, such as temperature. Increases in cold‐adapted diatom (Staurosirella pinnata, Staurosira construens, Staurosirella dubia) and chironomid (Sergentia) taxa between 12,900 and 11,700 cal yr BP coincided with Younger Dryas cooling, suggesting a direct link with summer temperature. Shifts in aquatic biota also reflected indirect mechanisms through which climate affected the Lake Stowell ecosystem, for example, by altering thermal stratification, disturbance regimes, and nutrient concentrations. For instance, high summer insolation and warm summer temperatures from 11,700 to 8500 cal yr BP were associated with greater abundances of Stephanodiscus hantzschii and especially Aulacoseira subarctica. A concurrent opening of the forest canopy triggered by warming would have exposed the lake to strong winds and enhanced mixing, favoring these more heavily silicified taxa as an indirect consequence of climatic changes. Diatom assemblages appear to have been impacted by the deposition of Mount Mazama tephra at 7600 cal yr BP; a notable increase in Aulacoseira tenella suggests a response to increased silica availability in association with tephra deposition.

Early–Middle Cambrian Palynomorph microfossils and related geochemical events in South China

The earliest Cambrian acritarch ‘Asteridium–Heliosphaeridium–Comasphaeridium’ assemblage and the Early Cambrian (‘Chiungchussuan’) acritarch ‘Skiagia ornate–Fimbriaglomerella membranacea’ assemblage in South China can be correlated with assemblages from synchronous strata elsewhere in the world. Recent geochemical study and biomarker evidence further confirm a biostratigraphic change between Cambrian Series 2 and Series 3 and support the recognition of a major geological and biotic event during this time interval.

Geological setting and paleoecology of the Upper Cretaceous Bench 19 Marine Vertebrate Bonebed at Bentiaba, Angola

AbstractThe Bench 19 Bonebed at Bentiaba, Angola, is a unique concentration of marine vertebrates preserving six species of mosasaurs in sediments best correlated by magnetostratigraphy to chron C32n.1n between 71.4 and 71.64 Ma. The bonebed formed at a paleolatitude near 24°S, with an Atlantic width at that latitude approximating 2700 km, roughly half that of the current width. The locality lies on an uncharacteristically narrow continental shelf near transform faults that controlled the coastal outline of Africa in the formation of the South Atlantic Ocean. Biostratigraphic change through the Bentiaba section indicates that the accumulation occurred in an ecological time dimension within the 240 ky bin delimited by chron 32n.1n. The fauna occurs in a 10 m sand unit in the Mocuio Formation with bones and partial skeletons concentrated in, but not limited to, the basal 1–2 m. The sediment entombing the fossils is an immature feldspathic sand shown by detrital zircon ages to be derived from nearby granitic shield rocks. Specimens do not appear to have a strong preferred orientation and they are not concentrated in a strand line. Stable oxygen isotope analysis of associated bivalve shells indicates a water temperature of 18.5°C. The bonebed is clearly mixed with scattered dinosaur and pterosaur elements in a marine assemblage. Gut contents, scavenging marks and associated shed shark teeth in the Bench 19 Fauna indicate biological association and attrition due to feeding activities. The ecological diversity of mosasaur species is shown by tooth and body-size disparity and by δ13C analysis of tooth enamel, which indicate a variety of foraging areas and dietary niches. The Bench 19 Fauna was formed in arid latitudes along a coastal desert similar to that of modern Namibia on a narrow, tectonically controlled continental shelf, in shallow waters below wave base. The area was used as a foraging ground for diverse species, including molluscivorusGlobidens phosphaticus, small species expected near the coast, abundantPrognathodon kianda, which fed on other mosasaurs at Bench 19, and species that may have been transient and opportunistic feeders in the area.

Pennsylvanian to Lower Permian (Desmoinesian-Wolfcampian) fusulinid biostratigraphy of Midcontinent North America

Midcontinent North American Middle Pennsylvanian-Lower Permian (Desmoinesian-Wolfcampian) fusulinid foraminiferal species range charts were plotted and new fusulinid zones were defined. The species range charts were plotted together with lithostratigraphic columns and cyclothemic sea level curves in order to compare biostratigraphic, lithostratigraphic, and glacio-eustatic patterns. The fusulinids Beedeina and Wedekindellina appeared during widespread early Desmoinesian transgressions and characterized that interval. The mid-Desmoinesian extinction of Wedekindellina and turnover of Beedeina species coincided with a lowstand followed by a widespread transgression, generally higher sea levels, and changing paleoclimatic patterns. Beedeina went to extinction near the Desmoinesian-Missourian sequence boundary. The earliest Missourian is barren of fusulinids in the Midcontinent, followed by a thin zone of Eowaeringella, and then the appearance of Triticites, which dominated fusulinid faunas through the remainder of the Upper Pennsylvanian. Lower and Middle Missourian Triticites have relatively small tests and plane septa. In the Upper Missourian, Triticites became medium-sized with more complex septal fluting, and Kansanella appeared. In the uppermost Missourian and lower Virgilian, most Triticites are medium-sized and evenly biconvex, and have weak septal fluting. Kansanella gradually declined through the lower Virgilian and disappeared in the lowest middle Virgilian. The middle Virgilian is dominated by medium to large Triticites with complex septal fluting, and Dunbarinella appeared and became locally common. The upper Virgilian has mostly large inflated Triticites and the first Leptotriticites. The uppermost Virgilian (‘Bursumian’) has large Triticites, diverse Leptotriticites, and the first primitive elongate Schwagerina. That fauna extends across the new conodont-based Pennsylvanian-Permian (Virgilian-Wolfcampian) boundary, and the first definitive Wolfcampian (Lower Permian) fusulinids did not appear until the Neva Limestone, which is a couple cycles above the new systemic boundary. Most significant fusulinid biostratigraphic changes correlate with major glacio-eustatic cyclothem boundaries, but not all major cyclothem boundaries have significant faunal turnovers. Fusulinid zonal boundaries that were based on only fusulinid species ranges were found to closely approximate maximum sea level lowstands. Most new genera and species appear in the regressive phases of the next cyclothem, probably because faunal migrations occurred during maximum flooding events, and subsequent highstand system tracts had more paleoenvironmental diversity and thus more niches to fill.

Plio-Pleistocene transition in the continental record from Lake Baikal: Diatom biostratigraphy and age model

Lake Baikal basin in the continental interior Asia preserved a unique continuous sedimentary archive of the late Cenozoic; large-scale regional environmental changes of the past were recorded in the composition of fossil diatom flora. Here, the Lake Baikal planktonic diatom biostratigraphy is extended over the Plio-Pleistocene transition, it includes 11 new local diatom assemblage zones (LDAZ) for the time interval 1.25–3.6 Ma. The comparison of the parallel BDP-96-1 and BDP-98 drill core records allows constructing the complete diatom biostratigraphic record at the time of the inception of the Northern Hemisphere glaciations; diatom biostratigraphic zones around Matuyama/Gauss paleomagnetic reversal are correlated with individual stages of marine oxygen isotope stratigraphy. Contrary to previous assumptions, the period 2.8–2.6 Ma in Lake Baikal record was characterized not by a prolonged minimum in diatom abundance but by a distinct maximum in the abundance of small-celled diatom taxa Tertiarius baicalensis and Stephanodiscus binderanus et var. hyalinus, which proliferated in the lake during the interval of relatively warm and humid climate. The Lake Baikal diatom biostratigraphic change at around 1.8 Ma occurs only at a species level of the genus Cyclotella. By contrast, around 2.8–2.5 Ma, spectacular appearances and extinctions occurred at a high taxonomic level of genera (including the genera of Tertiarius, Thalassiobeckia and Stepahanopsis) making the biostratigraphic changes around Matuyama/Gauss reversal more prominent. At least three distinct biostratigraphic boundaries are observed: at 2.69 Ma, 2.65 Ma and at 2.46 Ma. None of these boundaries, however, coincides with the paleomagnetic reversal at 2.58 Ma. Thus the new well-resolved Lake Baikal biostratigraphic record points to the difficulty of assigning a single ‘golden spike’ biostratigraphic boundary around Matuyama/Gauss paleomagnetic reversal in continental Asia.

New data regarding acritarch biostratigraphy from the Early-Middle Cambrian Kaili Formation in Chuandong, Guizhou Province, China

Previous studies had evaluated acritarchs from the Balang and Pingzhai sections of the Early-Middle Cambrian Kaili Formation in east Guizhou, China. The results of these studies suggest that the acritarchs in these sections have potential biostratigraphic significance. More recently, 34 samples collected from 83 m lower part of the Lower-Middle Cambrian Kaili Formation in the Jianshan section of Chuandong, Guizhou Province were prepared for palynological analysis. Analysis of these samples revealed a distinct change in the acritarch assemblages at the bed, which was approximately 46 m above the bottom of the Kaili Formation. These findings suggest a boundary represented by an important alteration of the ecological environment. In addition, the position of the acritarch biostratigraphic change is somewhat higher than the boundary between Cambrian Series 2 and Series 3 based on trilobites found in the same section. This indicates that the distinct change in acritarch assemblages is similar to the change in trilobite assemblages that occurs around the boundary between Cambrian Series 2 and Series 3. Therefore, acritarch biostratigraphy can provide data that can be used to define the base of Cambrian Series 3 in this region, and possibly worldwide.

Ammonoid succession at the Bajocian-Bathonian transition in the Bas Auran area, Digne district, South-East France.

The uppermost Bajocian to lowermost Bathonian ammonoid succession has been studied in the Bas Auran area in view of choosing one of its sections as the Global Stratotype Section and Point (G.S.S.P.) of the Bathonian Stage. The Bas Auran ammonite assemblages display exceptional values of record quality. The stratigraphic distribution of 629 specimens referred to 63 species and 35 genera, collected during the last forty years from three sections (Ravin du Bes, Ravin d'Auran, Ravin des Robines), is plotted and analyzed, bed by bed. Over 85 stratigraphic levels, through 9 m in thickness, have been studied at the top of the Marno-calcaires a Cancellophycus formation, ranging from the latest Bajocian (Parkinsoni Zone, Bomfordi Subzone) to the earliest Bathonian (Zigzag Zone, Convergens Subzone) and the base of the Macrescens Subzone. Ammonoid assemblages are composed of Northwest European and Mediterranean elements, associated with Sub-Mediterranean ones, allowing chronocorrelation between the Northwest European Convergens Subzone and the Sub-Mediterranean Parvum Subzone. The basal boundary of the Zigzag Zone and of the Bathonian Stage is placed at the base of Sturani's bed 23 in the Ravin du Bes section and is identified by the first occurrence of Gonolkites convergens, and coincides with the loest occurrence of Morphoceras parvum. Features of the ammonoid succession indicate relatively homogeneous and good record quality, gradual biostratigraphic change and high degree of taxonomic similarity between the Bomfordi and Convergens subzones. Palaeontological criteria also indicate relatively high values of palaeontological and stratigraphic completeness at the base of levels RB070-RB071 (= level 23 in Sturani 1967) which corresponds to the Bajocian/Bathonian boundary. The Ravin du Bes Section, with forty-six successive ammonoid fossil-assemblages of the Convergens Subzone belonging to three biohorizons through five metres of thickness, shows maximum values of biostratigraphic and biochronostratigraphic completeness, being one of the most complete in the world. Therefore, the Ravin du Bes Section should be chosen as the Global Stratotype Section and Point for the base of the Bathonian Stage. Two biostratigraphic logs summarize the ammonite content from the uppermost Bomfordi to basal Macrescens subzones. Three plates illustrate the most characteristic ammonoid taxa at the Bajocian-Bathonian passage in the Bas Auran succession.

Mio‐Pliocene magnetostratigraphy in the southern Carpathian foredeep and Mediterranean–Paratethys correlations

AbstractA full understanding of the Mio‐Pliocene palaeogeographical and palaeoenvironmental changes in the circum‐Mediterranean region during the Messinian Salinity Crisis (MSC) is at present hampered by the lack of reliable chronostratigraphic correlations between the Mediterranean and Paratethys regions. Here, we present magnetostratigraphic ages for the Upper Miocene to Pliocene deposits of the southern Carpathian foredeep in Romania. These ages are in good agreement with those recently obtained from the eastern Carpathian foredeep and define a new chronology for the eastern Paratethys. The Meotian/Pontian boundary is not biostratigraphically constrained in our sections, but according to the geological map of the region arrives at ∼5.8 Ma. The Pontian/Dacian boundary is dated at c. 4.8 Ma and the Dacian/Romanian boundary at c. 4.1 Ma. The main part of the MSC (5.96–5.33 Ma) is thus represented by the Pontian Stage, but the observed palaeoenvironmental and biostratigraphic changes in our sections of the eastern Paratethys do not indicate any relation with the dramatic desiccation and reflooding events of the Mediterranean.

New Biostratigraphic Evidence of the Post-Glacial Colonization of Ireland and for Mesolithic Forest Disturbance

Recent road works have exposed a thin but extensive deposit of calcareous tufa resting on till (Dublin Formation) at Newlands Cross near Tallaght, County Dublin. Close serial sampling and quantita- tive analyses of the contained fossils (non-marine Mollusca, ostracods and vertebrates) have been undertaken. The mollusc data reveal successional patterns that can be directly related to the vegetational history of the area by means of pollen analyses. A chronology for the more important biostratigraphic changes has been provided by radiocarbon dating using accelerator mass spectrometry. Thus the onset of tufa formation is dated at 9720?300 BP (OxA-569) during a Gramineae-Juniperus-Betula pollen assemblage zone. An open-country mollusc assemblage including several arctic-alpine species, e.g. Vertigo genesii, V. geyeri and notably Columella columella (new to the Irish Quaternary) existed at this time. This fauna was gradually replaced by a series of shade-demanding snails during the period of Corylus expansion. A thin buried soil horizon represents a brief period of retarded tufa growth when the land surface became relatively dry. A fresh flint-flake was recovered from this surface, which also marks the main expansion of the shade-demanding snail, Discus rotundatus. A radiocar- bon date of 7600?500 BP (OxA-568) was obtained from the fruits of Eupatorium cannabinum from the tufa immediately overlying this soil. The presence of Mesolithic man in the area is unequivocally demonstrated. Teeth of woodmouse (Apodemus sylvaticus) at this level confirm the native status of this species in Ireland. Other biostratigraphic changes in the upper levels of the tufa are almost certainly attributable to anthropogenic disturbance involving some forest clearance. Woodland conditions are again evident towards the top of the sequence and tufa formation, at this point, probably ceased by -7000 BP. This sequence, the most detailed yet reported from Ireland, is compared with equivalent sites in Britain and elsewhere and the biogeographic questions posed as regards the possible existence and timing of a landbridge connection are discussed.

Biostratigraphic Changes in Spore and Pollen Record in Middle to Upper Cretaceous of Atlantic Coastal Plain as Reflection of Sea-Floor Spreading, Global Cooling, and Evolution of Wind Pollination: ABSTRACT

During the middle Albian and continuing through the late Cenomanian, changes in the spore and pollen record of the Middle Atlantic Coastal Plain suggest cooling climatic trends. The decrease in temperature is indicated by a reduction in palynomorphs associated with humid tropical conditions and an increase in gymnosperm pollen. These trends are paralleled by a gradual but continuous evolution of angiosperm types from tricolpate to triporate pollen. The latter events may be associated with cooling and increasing seasonality that would favor selective pressures for the evolution from early insect-pollinated angiosperms to well-developed wind-pollinated types by late Cenomanian. This climatically driven evolutionary trend reaches its acme during the Coniacian-Santonian clima ic maximum. Climatic cooling during the middle Cretaceous, as suggested by oxygen isotope studies, is believed to be related to increased sea-floor spreading. Such plate movements resulted in the fractionation of the circumglobal tropical Tethyan seaway as well as an increasing rate of northward and counterclockwise movement of the Middle Atlantic coastal margin during middle to Late Cretaceous times. End_of_Article - Last_Page 1659------------