Stratotype Section Research Articles

Landscape and climat changes in Eastern Europe in the early Pleistocene

The systematization of the original and published data on the geology and paleogeography of the Late Pliocene and Early Pleistocene of Eastern Europe was carried out due to the lowering of the Quaternary lower boundary to the level of 2.6 million years ago and the inclusion of the Gelasian stage in Quaternary system. It was revealed that at the bound of the Gauss-Matuyama paleomagnetic epochs, the profound landscape and climate changes took place. The rhythmic fluctuations of the climate intensified against the background of the general trend towards cooling and aridization. Subarctic landscapes appeared during the period from 2.6 to 1.8 Ma, which corresponds to the Gelasian stage (the Praetiglian and Tiglian stages of Western Europe or the Paleopleistocene of Eastern Europe). In the Eopleistocene (1.8–0.78 Ma) and Early Neopleistocene (0.78–0.42 Ma), the climate became colder while the structure of natural zonality repeatedly underwent a complex restructuring and gradually approached to the modern one. The presence of glacial deposits was noted in Eastern Europe already in the Paleopleistocene. The traces of at least three independent glaciations were revealed in the Eopleistocene, and four glaciations were suggested for the Early Neopleistocene. Based on the data from stratotype sections, paragenetic relations between heterochronous sediments in glacial and periglacial areas were established and Early Pleistocene paleogeographic events in Eastern and Western Europe were correlated.

Accuracy and precision of the late Eocene–early Oligocene geomagnetic polarity time scale

AbstractAn accurate and precise geomagnetic polarity time scale is crucial to the development of a chronologic framework in which to test paleoclimatic and paleoenvironmental interpretations of marine and terrestrial records of the Eocene–Oligocene transition (EOT). The magnetic polarity patterns of relatively continuous marine and terrestrial records of the EOT have been dated using both radio-isotopic techniques and astronomical tuning, both of which can achieve a precision approaching ±30 k.y. for much of the Paleogene. However, the age of magnetic reversals between chrons C12n and C16n.2n has proved difficult to calibrate, with discrepancies of up to 250 k.y. between radio-isotopically dated and astronomically tuned marine successions, rising to 600 k.y. for comparisons with the 206Pb/238U-dated terrestrial record of the White River Group in North America. In this study, we reevaluate the magnetic polarity pattern of the Flagstaff Rim and Toadstool Geologic Park records of the White River Group (C12n–C16n.2n). Our interpretation of the Flagstaff Rim polarity record differs significantly from earlier studies, identifying a previously unreported normal polarity zone correlated to C15n, which eliminates discrepancies between the WRG and the 206Pb/238U-dated marine record of the Rupelian Global Stratotype Section and Point in the Italian Umbria-Marche basin. However, residual discrepancies persist between U-Pb–dated and astronomically tuned records of the EOT even when stratigraphic and systematic uncertainties associated with each locality and dating method are taken into account, which suggests that the uncertainties associated with astronomically tuned records of the EOT may have been underestimated.

Geoheritage importance of stratigraphic type sections, type localities and reference sites—review, discussion and protocols for geoconservation

Equivalent in principle to type localities and type specimens in biology and paleontology, geological type sections and type localities, whether for sedimentary, metamorphic or igneous units, are critically important sites as long-term reference and research localities and for geo-education of students. Unlike type specimens that are housed in museums or established institutions of learning, most geological type sections and localities are in field settings and, if they are not located in National Parks or other reserves with some legislated protection, run the risk of being destroyed, inundated, buried by earthworks or otherwise modified. The history of the geological sciences in Australia is such that a number of type localities, or stratigraphic type sections, have been destroyed by local government actions, or developers through lack of knowledge of their importance, or lack of knowledge of their existence. Examples of the severe modification or loss of type sections include those of the Maxicar beds, the Tims Thicket Limestone and the Eaton Sand. The UK, a leader in the field of Geoconservation and with a number of global stratotype section and point locations as well as many other type sections identified within its borders, provides models for preserving and managing important geological sites and type sections. Whole-of-government and local governments are involved in the registering and protection of important geological sites. Aspects of the UK model may be adapted to help secure geological type sections and localities in Australia. While some type sections and heritage localities are already protected, to improve the level of protection for more sites we propose a long-term, multi-pronged approach: creation of an inventory of all nominated locations; registration of appropriate sites at Local, State or Federal government levels, where current legislation allows; education of landowners and land managers, both government and non-government to highlight the importance of type sections to science; and securing more geological type sections and localities in some form of reserve.

A new possible bivalve burrow Oblongichnus solodukhoi from the late Kazanian (middle Permian) stratotype section in Russia

A burrow previously assigned to the ichnotaxon Palaeophycus insignis is redescribed, and a new ichnotaxon Olongichnus solodukhoi n. igen. n. isp is erected for this flattened, slightly curved, multi-oriented, smooth burrow that has a thick lining with internal and external very fine-grained mucuous layers. It shows subrectangular to oblong form in cross section. O. solodukhoi is collected from the lowermost part of the Member D (Seryi Kamen Member, Pechishchi Beds) of the late Kazanian (middle Permian) stratotype section (East European Platform). It occurs in yellowish grey dolostone formed within open shallow-marine environments. O. solodukhoi records combined feeding and dwelling behaviours of a suspension-feeding organism. It could be produced by burrowing organisms with a simple flattened morphology, such as flatworms or polychaetes; however, we favour elongate and ultra-elongate bivalves as the potential tracemakers of the reported burrows.

Conservation and Sustainable Development of Geoheritage, Geopark, and Geotourism: a Case Study of Cenozoic Successions of Western Kutch, India

Geoheritage is a concept concerned with the preservation of features with importance to earth science, such as landforms, natural exposures of rocks, and sites where geological features can be examined for further study, reference, and conservation for coming generations. Geoheritage, geoconservation, and geotourism studies are gaining interest worldwide because of their scientific, academic, historical, societal, cultural, and esthetic values. Several countries have their government policy to look after the geoheritage sites and conserve with the help of local agencies; however, in India, the concept is still to be applied in a holistic way, and there is a need of such national legislation. Kutch basin as a whole preserves the records of sedimentation for the past ~ 200 Ma. The Cenozoic (last 65 Ma.) sedimentation (~ 900 m) is considered a strato-type section for the shallow-marine sedimentary records in India. Some Cenozoic sections of Kutch are the only remained reference sections of the respective periods on the globe. This sedimentary succession acts as a geological museum for paleontology, stratigraphy, biostratigraphy, and sequence stratigraphy. Such records of past climates and sea-level fluctuations are characterizing the global sea-level history. It also provides an outcrop analog for reservoir rocks of Bombay High oil field. Taking this into account, we propose seven selected sites in the Cenozoic succession to be preserved as geoheritage sites and development of geotourism in the region viz. Matanomadh cliff section, Naredi cliff section, Fulra limestone section, Miocene succession, Paleosol of Sandhan Formation, Kharai River paraconformity section, and Bermoti River section. The advantage of a geopark comprises also in creating new employment opportunities for local youths. Further, it will help enhance the local economy by infrastructure development, health, and educational pursuits to the village-level society. The prime objective of this investigation is to make local people aware about sustainable mining and insatiable thrust for money that threatens ecologically important sites. The geological records are the consequences of millions of years of processes and are considered precious which require special care. If these records once destroyed will be lost forever and cannot be restored artificially, it is our prime responsibility to transfer the knowledge and geoheritage to future generations.

High-resolution 10Be and paleomagnetic recording of the last polarity reversal in the Chiba composite section: Age and dynamics of the Matuyama–Brunhes transition

We present new magnetic (direction and relative paleointensity) and beryllium isotope (10Be, 9Be and 10Be/9Be ratio) results covering the last geomagnetic reversal, i.e., the Matuyama–Brunhes transition (MBT), from the Chiba composite section (CbCS), east-central Japan. The very high sedimentation rates (>90 cm/ka) of the studied site, a candidate site for the global boundary stratotype section and point (GSSP) of the Lower–Middle Pleistocene boundary, allow the acquisition of a dataset of exceptional resolution. Coupled cosmogenic 10Be and magnetic results measured on the same samples demonstrate that the magnetization acquisition conserved the timing of rapid geomagnetic features, allowing accurate paleomagnetic interpretations. A polarity switch (PS) capturing most of the angular deviation occurring between 771.9 and 773.9 ka was followed by a directional instability rebound (IC1) until 768.5 ka. This sequence with 5.4 ka duration was characterized by a weak dipole field as low as 2.3 ± 0.3 × 1022 Am2. Four rapid episodes of directional instabilities preceding and following the PS-IC1 phase completed the reversal sequence. The asymmetry observed between the long-term dipole decay and sharp recovery, and rapid oscillations (<1 ka) demonstrate the complex transitional field behavior during dipole moment low before reestablishment of the full polarity state. Our observations reinforce the fact that most reversal records do not integrate the full field behavior associated with the geodynamo action. Although this poses problems for understanding the underlying physical processes that produce reversals, it does not hamper stratigraphic correlations among most geologic records.

Characterization of the calcareous nannofossil assemblages across the Latest Danian Event (LDE) at Wadi El-Maheer, northern Eastern Desert, Egypt

High resolution calcareous nannofossil analyses of the Danian-Selandian (D-S) transition are carried out at Wadi El-Maheer section, northern Eastern Desert, Egypt. The detailed analyses lead to subdivide the NP4 Zone into six subzones (NTp5C- NTp6, NTp7A, NTp7B, NTp8A, NTp8B, and NTp8C). The main events observed at the studied section are well correlated to those observed at the Global Stratotype Section and Point (GSSP) for the base of the Selandian at Zumaia as well as Caravaca sections (Spain) and Qreiya section (Egypt) with minor discrepancies. The first and second radiation of fasciculiths are recorded and characterized by successive coinciding events. These two radiations are separated by an interval that lacked to fasciculiths. This interval seems to be synchronous across the Tethyan region and South Atlantic within the NTp8A Subzone. Therefore, this interval could represent an applicable event to correlate the D-S transition across different paleo-latitudes. The Latest Danian Event (LDE) is identified within the NTp7B Subzone. The calcareous nannofossil assemblages patterns during this event reflect short warming episode resemble to the Paleocene Eocene Thermal Maximum (PETM) but with a lesser degree.

Exact dating of the Meghalayan lower boundary based on high-latitude tree-ring isotope chronology

Subdivision of the Holocene Series/Epoch into the Greenlandian, Northgrippian and Meghalayan Stages/Ages has recently been ratified based on stable isotope records from ice-core and speleothem archives. The base of the most recent chronostratigraphic unit, corresponding to the Northgrippian−Meghalayan boundary, coincides with the ‘4.2 ka event’ recognised as a low-latitude drought anomaly. The Global Stratotype Section and Point (GSSP) for the boundary, the oxygen isotope record from the Mawmluh Cave speleothem (India), demonstrates this event with markedly weakened Asian summer monsoon. Here we contribute to the assessments of the geological time scale and the global characteristics of this event by detailing an isotopic excursion in tree-ring carbon isotopes from high-latitude/subarctic Europe. The δ13C chronology demonstrates extremely overcast (wet) conditions, especially between 2190 and 2100 BCE, with anomalous conditions sustaining until 1990 BCE. In addition to demonstrating its exact dating and duration, the δ13C data also illustrate the two-stage nature of the event and highlight the greater magnitude of the earlier stage. This reinforces the characterisation of this ‘Meghalayan anomaly’ in the context of other proxy-sites around the world. The North Atlantic forcing, previously associated with weakened Asian summer monsoon, accords with the suggested roles of North Atlantic Oscillation and/or southwards shift of Inter-Tropical Convergence Zone in producing the hydroclimatic anomaly. In fact, it would be clarifying to separate the hydroclimatic ‘Meghalayan anomaly’ from the broadly cited and potentially longer lasting ‘4.2 ka event’, to analyse their respective forcing mechanisms. We conclude by dating the Meghalayan lower boundary to 2190 BCE.

BP Gulf of Mexico Neogene Astronomically-tuned Time Scale (BP GNATTS)

AbstractThis paper introduces an integrated Neogene microfossil biostratigraphic chart developed within post-merger BP for the Gulf of Mexico Basin and is the first published industrial framework “fully-tuned” to orbital periodicities. Astronomical-tuning was accomplished through a 15-year research program on the Ocean Drilling Program’s (ODP) Leg 154 sediments (offshore NE Brazil) with sampling resolution for calcareous nannofossils and planktonic foraminifera ∼20 k.y. and 40 k.y. (thousand year), respectively. This framework extends from the Late Oligocene (25.05 Ma) to Recent at an average Chart Horizon resolution for the Neogene of 144 k.y., approximately double that of published Gulf of Mexico biostratigraphic charts and a fivefold increase over the highest resolution global calcareous microfossil biozonation. Such resolution approximates that of fourth to fifth order parasequences and is a critical component in the verification of seismic correlations between mini-basins in the deep-water Gulf of Mexico. Its utility in global time-scale construction and correlation has been proven, in part, by application of the scheme in full to internal research for the Oligocene–Miocene boundary interval on the global boundary stratotype section and point (GSSP) in northern Italy and offshore wells in the eastern Mediterranean Sea. This step change in Neogene resolution, now at the level of cyclostratigraphy (the orbital periodicity of eccentricity) and the magnetostratigraphic chron, demonstrates the potential for calcareous microfossil biostratigraphy to more consistently reinforce correlations of these time scale parameters. The integration of microfossil disciplines, consistent taxonomies, and rigorous analytical methodologies are all critical to obtaining and reproducing this new level of biostratigraphic resolution.

Subdividing the Holocene Series/Epoch: formalization of stages/ages and subseries/subepochs, and designation of GSSPs and auxiliary stratotypes

ABSTRACTThe Holocene, which currently spans ~11 700 years, is the shortest series/epoch within the geological time scale (GTS), yet it contains a rich archive of evidence in stratigraphical contexts that are frequently continuous and often preserved at high levels of resolution. On 14 June 2018, the Executive Committee of the International Union of Geological Sciences formally ratified a proposal to subdivide the Holocene into three stages/ages, along with their equivalent subseries/subepochs, each anchored by a Global boundary Stratotype Section and Point (GSSP). The new stages are the Greenlandian (Lower/Early Holocene Subseries/Subepoch) with its GSSP in the Greenland NGRIP2 ice core and dated at 11 700 a b2k (before 2000 CE); the Northgrippian (Middle Holocene Subseries/Subepoch) with its GSSP in the Greenland NGRIP1 ice core and dated at 8236 a b2k; and the Meghalayan (Upper/Late Holocene Subseries/Subepoch) with its GSSP in a speleothem from Mawmluh Cave, north‐eastern India, with a date of 4250 a b2k. We explain the nomenclature of the new divisions, describe the procedures involved in the ratification process, designate auxiliary stratotypes to support the GSSPs and consider the implications of the subdivision for defining the Anthropocene as a new unit within the GTS.

Jurassic–Cretaceous boundary bioevents and magnetochrons: A stratigraphic experiment

The search for an Upper Jurassic–Lower Cretaceous Global Boundary Stratotype Section and Point has been elusive. Few evolutionary events are dramatic at this transition and paleoenvironmental and tectonic changes are subtle and local. Ammonites, calpionelids, calcareous nannofossils, and paleomagnetic reversals are the principle events that distinguish Tithonian-Berriasian–Valanginian stages.This quantitative stratigraphic experiment integrates the first and last occurrences of bioevents (FOs/LOs) with magnetochrons from biostratigraphic checklists of measured sections and cores. Events in forty-one well documented outcrops and deep-sea cores were cross-plotted in X/Y diagrams with a geologic time scaleto create hypotheses of synchroneity between section pairs. The correlation line of synchroneity extended the FOs and LOs in each section relative to other sections. The composited range extensions in all sections approximate first- and last-appearance datums (FADs, LADs) and comprise a database (LOK2016CS) calibrated to numerical ages (Ma). Two sections have reported radioisotope ages that constrain the ages of taxa. This stratigraphic experiment places the calpionellid, nannofossil and ammonite FADs in the predicted order relative to magnetochrons.The base of the Berriasian Stage is approximated by the FAD of Calpionella alpina, which is in uppermost M20n. Asssociated key nannofossil FADs are Nannoconus globulus globulus, Crucielllipsis cuvillieri, and Zeugrhabdotus erectus. The LAD of Crassicollaria intermedia is also close to these events. Base of the middle Berriasian Substage is the FAD of Subthurmannia subalpina at the base of the Subthurmannia occitanica Zone close to the base of Chron M18. Base of the upper Berriasian Substage is the FAD of Malbosiceras [Mazenoticeras] paramimounum at the base of the Subthurmannia boiseri Zone at about the boundary between chrons M17 and M16. The base of the Valanginian Stage is at the FAD of Thurmanniceras pertransiens and Calpionellites darderi and above the FAD of Calcicalathina oblongata, which correlates with the Chrons M15/M14. The base of the upper Valanginian is at the base of the Saynoceras verrucosum Zone in Chron M10n.

40Ar-39Ar step heating ages of North American tektites and of impact melt rock samples from the Chesapeake Bay impact structure

Abstract This study presents 40Ar-39Ar step heating ages of four North American tektites (three bediasites and one georgiaite) and of two groundmass samples extracted at different depths from clast-rich impact melt rocks (CB-W61 and CB-W84) recovered by the USGS-ICDP Eyreville B drill-core about 9 km from the centre of the Chesapeake Bay impact structure. Radiometric age determination on both North American tektites and impact melt rocks from within Chesapeake Bay crater offers the first possibility to confirm the origin of these tektites. For this aim, argon isotopic data from 13 samples/aliquots of tektite rims, cores and bulk, and 4 samples/aliquots from two impact melt rocks were obtained over 15 to 26 step heating extractions. Age spectra of all tektite samples show plateaux comprising 62–98% of the 39Ar release over consecutive intermediate and high temperature heating steps. Few low temperature extractions indicate excess 40Ar. Inverse isochron 40Ar/36Ar intercepts of tektite samples are indistinguishable from air (295.5). However, impact melt rock spectra presented complex Ar-release affecting primarily the low temperature heating-steps. Inverse isochrones indicate excess argon from which the 40Ar/36Ar intercept was used to correct the age calculation. CB-W61 and CB-W61-2 40Ar/36Ar intercepts are 354.5 ± 2.5 and 327.2 ± 6.3, respectively, and those for CB-W84 and CB-W84-2 are 332.0 ± 7.3 and 329.6 ± 5.6, respectively. The inverse isochron weighted mean age (according to currently suggested K-decay constants revisions by Schwarz et al. (2011) and Renne et al. (2011)) for all four tektites is 34.86 ± 0.25 Ma (MSWD = 0.96, P = 0.41; n = 4) and for the two impact melt rocks is 37.16 ± 3.65 Ma (MSWD = 0.83, P = 0.36). The combined tektite and impact melt rocks isochron mean age of 34.86 ± 0.23 (0.32) Ma (MSWD = 0.87, P = 0.43) is slightly – though not significantly – higher than the plateau mean age of 34.55 ± 0.27 (0.36) Ma (MSWD = 0.66, P = 0.62). Placing this age in the Global Stratotype Section and Point (GSSP) marine section exposed at Massignano, Italy, it falls below the Eocene/Oligocene (E/O) boundary overlapping with the 10.28 m Ir-anomaly. These results agree within errors with previously reported ages of 35.20 ± 0.54 Ma, especially those derived from K-Ar and Ar-Ar total fusion analysis. An age of 34.86 ± 0.32 Ma sets the Chesapeake Bay impact event close to the youngest of the three Ir anomalies at ∼35.0 Ma in the case the impactor was Ir-rich (e.g, a chondrite, primitive achondrite, stony-iron or iron meteorite). The concordance with the E/O boundary at ∼33.9 Ma seems only marginally possible, and only if the Ir contribution from the ejecta were, potentially, due either to its small amount becoming diluted in the geologic record or the impactor being Ir poor, e.g., of differentiated achondritic composition. This study also brings to front the need to re-establish the stratigraphic and palaeo-magnetic correlations across the globe for the Ir-anomalies and the magneto-stratigraphy during the mid- to late-Eocene and early-Oligocene, and the need to re-evaluate the markers for the Eocene-Oligocene boundary.

Integrated Quantitative Calcareous Plankton Bio-Magnetostratigraphy of the Early Miocene from IODP Leg 342, Hole U1406A, Newfoundland Ridge, NW Atlantic Ocean

High-resolution quantitative analyses of the planktonic foraminifera and calcareous nannofossil content have been carried out on IODP Leg 342, Hole U1406A (Northwest Atlantic Ocean) in the core interval 10H2–2H4, plotting the abundance distributions of the biostratigraphically and quantitatively most significant species. Qualitative analyses have been used to identify the precise depth of marker bioevents. For almost the whole succession, relevant magnetostratigraphic data were provided by previous studies. All chrons and subchrons in the interval C6Cn–C6AAr were recognised in core interval 10H2–4H1 and calibrated to the GPTS 2012, but no magnetostratigraphic data are available for the highest portion (above 35 m). The investigated succession falls between Sphenolithus delphix FO (First Occurrence)—uppermost Chattian bioevent—in core 10H2 and the Sphenolithus belemnos LO (Last Occurrence)–Burdigalian bioevent – in core 2H5, embracing the Zone O7 (uppermost part)–M3 foraminiferal zone interval and the Zone CNO6–CNM5 calcareous nannofossil zone interval. A calcareous plankton biochronological framework has been produced integrating calcareous plankton and magnetostratigraphic data. Calculated ages for the most significant recognised bioevents are S. delphix FO 23.35 Ma, S. delphix LO 23.02 Ma, Paragloborotalia kugleri FO 23.00 Ma, Globoquadrina dehiscens FO 22.59 Ma, Sphenolitus disbelemnos FO 22.56 Ma, Helicosphaera carteri FCO (First Common Occurrence) 22.18 Ma, P. kugleri LO 21.23 Ma. Two hiatuses have been recognised within core 4H, whereas only one was recognised in previous studies. The first one in core 4H5 spans the interval 21.17–19.01 Ma and coincides with a phosphate-rich layer; the second in core 4H2 spans the interval from 18.87 to 18.21 Ma and corresponds to a glauconite-rich layer. The results obtained from Hole U1406A allow some considerations about potential reference bioevents concerning the still open issue of Burdigalian GSSP (Global Stratotype Section and Point).

Formal Subdivision of the Holocene Series/Epoch: A Summary

Abstract The Holocene Series/Epoch is the most recent series/epoch in the geological timescale, spanning the interval from 11,700 yr to the present day. Together with the subadjacent Pleistocene, it comprises the Quaternary System/Period. The Holocene record contains diverse geomorphological, biological, climatological and archaeological evidence, within sequences that are often continuous and extremely well-preserved at decadal, annual and even seasonal resolution. As a consequence, the Holocene is perhaps the most intensively-studied series/epoch within the entire Geological Time Scale. Yet until recently little attention had been paid to a formal subdivision of the Holocene. Here we describe an initiative by the Subcommission on Quaternary Stratigraphy (SQS) of the International Commission on Stratigraphy (ICS) to develop a formal stratigraphical subdivision of the Holocene, with three new stages/ages, two underpinned by Global Boundary Stratotype Sections and Points (GSSPs in an ice core, and a third in a speleothem. These stages/ages are defined together with their equivalent subseries/subepochs. The new stages/ages are the Greenlandian with its GSSP in the Greenland NGRIP2 ice core and dated at 11,700 yr b2k (before 2000 CE); the Northgrippian with its GSSP in the Greenland NGRIP1 ice core and dated to 8236 yr b2k; and the Meghalayan, with its GSSP in a speleothem from Mawmluh Cave, northeastern India, with a date of 4250 yr b2k. This subdivision was formally ratified by the Executive Committee of the International Union of Geological Sciences (IUGS) on 14th June 2018.

A summary of the Chiba Section, Japan

We propose the extensively studied Chiba section of the Chiba composite section (CbCS) as the Global Boundary Stratotype Section and Point (GSSP) to define the base of the Middle Pleistocene Subseries and Chibanian Stage. The CbCS is a continuous and expanded marine sedimentary succession within the middle of the Ko-kumoto Formation, Boso Peninsula, Chiba Prefecture. It contains well-preserved pollen, marine micro-and macrofossils, a tightly-defined Matuyama-Brunhes (M-B) paleomagnetic polarity boundary, and numerous tephra beds, allowing the establishment of a robust and precise chronostratigraphic framework across the Lower-Middle Pleistocene boundary. Its deep-marine, open-ocean continental slope setting, coupled with high sedimentation rates with no evidence of abrupt deposition, has resulted in preserving both terrestrial and marine environmental changes in and around Marine Isotope Stage (MIS). We have performed high-resolution oxygen isotope analysis , as well as detailed sedimentological, geochemical, and biostrati-graphic studies of the CbCS, confirming the completeness of the stratigraphic interval spanning the Lower-Middle Pleistocene boundary. The M-B polarity boundary serves as the agreed primary guide for the Lower-Middle Pleistocene boundary, and the CbCS represents one of the most detailed marine sedimentary records yet obtained for this reversal, yielding an astronomical age of. ka with a duration of ca.. kyr. This section therefore offers an exceptional opportunity to calibrate the geological time scale as well as understand the dynamics of the geodynamo. The widespread Byk-E tephra lies close to the reversal, allowing precise regional lithostrati-graphic correlation. The CbCS is easy to access from international airports. The section will be permanently preserved and maintained by the local government as a natural monument. Based on these attributes , the base of the Byk-E tephra bed in the Chiba section is the best horizon for establishing the GSSP that will define the Lower-Middle Pleistocene boundary.

The Middle Jurassic palynostratigraphy of the northern Lusitanian Basin, Portugal

A composite largely Middle Jurassic succession spanning the Toarcian-Aalenian transition to the lowermost Bathonian exposed at Cabo Mondego and Sao Giao in the northern Lusitanian Basin, western Portugal, was examined palynologically. The 129 samples are correlated to ammonite biozones spanning Pleydellia aalensis to Zigzagiceras zigzag. The Cabo Mondego succession comprises the type section of the Cabo Mondego Formation and spans virtually the entire interval studied. This is a significant interval because it includes the Global Stratotype Section and Point (GSSP) and the Auxiliary Stratigraphical Section and Point (ASSP) for the Bajocian and Bathonian stages respectively. The Cabo Mondego Formation largely yielded relatively abundant palynomorph associations in the 68 productive samples recovered. By contrast, the Povoa da Lomba Formation at Sao Giao only includes the Toarcian-Aalenian transition; the 21 productive horizons produced sparse assemblages. The uppermost Toarcian to lowermost Bajocian is characterised by a low diversity dinoflagellate cyst association, typified by Nannoceratopsis. Above this is a markedly more diverse assemblage. This influx, in the Witchellia laeviuscula ammonite biozone AB, represents a global evolutionary radiation which may be linked to sea level rise. The trend of increasing dinoflagellate cyst diversity continued at the Bajocian-Bathonian transition. The Middle Jurassic dinoflagellate cyst assemblages of the Lusitanian Basin are significantly less diverse than coeval palynobiotas from eastern and northern Europe, and the Arctic. The Toarcian Oceanic Anoxic Event (T-OAE) profoundly inhibited cyst-forming dinoflagellates in this depocentre, and the recovery was protracted. Hence the T-OAE may have suppressed dinoflagellate cyst diversity well into the Middle Jurassic. This phenomenon may have been exacerbated by the absence of typically Arctic taxa through latitudinal controls and/or global cooling during the early Aalenian. These low levels of dinoflagellate cyst species richness may also be related to the palaeogeography of the Lusitanian Basin. This relatively isolated deepwater depocentre close to the Proto Atlantic, may have precluded extensive biotal exchange with the widespread shelfal areas of the western Tethys. The absence of Dissiliodinium giganteum in the Lusitanian Basin is consistent with this scenario. The pollen and spores observed in this study are typical of Middle Jurassic assemblages worldwide. Araucarian pollen, largely Callialasporites, diversified and became prominent during the Aalenian.

A dinoflagellate cyst zonation of the Cenomanian and Turonian (Upper Cretaceous) in the Western Interior, United States

This study documents the detailed palynology of the Bridge Creek Member, Greenhorn Limestone Formation, at the Rock Canyon anticline outcrop, west of Pueblo, Colorado, USA. The section is the formally ratified Global Boundary Stratotype Section and Point (GSSP) for the base of Turonian Stage and corresponding Lower Turonian Substage, and the only proposed GSSP for the base of the Middle Turonian Substage. The authors’ previously published palynological data from the underlying Cenomanian strata in the nearby US Geological Survey (USGS) Portland-1 core, and from cores and an outcrop of Cenomanian, Turonian and earliest Coniacian age in SW Texas, are reviewed for biostratigraphy. Dinoflagellate cyst ranges and events in both areas are calibrated against other published bio- and chemostratigraphical (carbon isotope) data and an astronomical age model. A regional dinoflagellate cyst zonation is proposed, adapted from a Central and Northern European scheme, comprising three zones and four subzones. Comparison with vintage published palynological data from other states, including Arizona, Kansas, Utah, Wyoming and Montana, indicates that the zonation is probably applicable to marine sections throughout the Cretaceous Western Interior Seaway of the USA. The new palynological data from around the Lower–Middle Turonian boundary at Pueblo support its proposal as a GSSP.

Formal subdivision of the Quaternary System/Period: Present status and future directions

The Quaternary System/Period and Pleistocene Series/Epoch were defined in 2009 by the Global boundary Stratotype Section and Point (GSSP) for the Gelasian Stage/Age (2.58 Ma), which aligns with Marine Isotope Stage (MIS) 103 and approximates the Gauss–Matuyama Chron boundary, contrary to earlier reports. The Vrica GSSP (1.80 Ma) was repurposed in 2011 to define the Calabrian Stage, effectively completing the Lower Pleistocene Subseries/Subepoch. The candidate for the Middle Pleistocene Subseries (and proposed Chibanian Stage) GSSP (∼774 ka) is the Chiba section, Japan. It aligns with MIS 19 and approximates the Matuyama–Brunhes Chron boundary (∼773 ka). The Upper Pleistocene Subseries, with a base traditionally marked by the onset of the Last Interglacial, is not yet defined by GSSP. The Holocene Series/Epoch was formally defined in 2008 by a GSSP in the NGRIP2 Greenland ice core with an age of 11,700 yr b2k (before 2000 CE) and in 2018 was subdivided, using climatic events at 8.2 and 4.2 ka, into the Greenlandian, Northgrippian and Meghalayan stages/ages and their corresponding Lower/Early, Middle, Upper/Late subseries/subepochs. The Northgrippian GSSP (8236 yr b2k) is defined in the NGRIP1 Greenland ice core, and the Meghalayan GSSP (4250 yr b2k) in a speleothem from Meghalaya, India. This subdivision formally introduces the rank of subseries/subepoch, and incorporates by far the briefest of all stages into the geological time scale. Using ice cores and a speleothem for GSSPs is unique to the Holocene. The presently undefined term Anthropocene is already used extensively and, like Holocene subdivisional terms, its functionality will be enhanced by formal definition. The Anthropocene should not be confused with anthropogenic: it reflects a tipping point in the Earth System response to the marked intensification of human impacts, not simply the fact of human impact. The geological Anthropocene, as currently envisioned, would start in the mid-twentieth century, holding the rank of series, and terminating the Holocene but not interfering with its subdivision other than to terminate the Meghalayan Stage.

UPPER SPATHIAN TO BITHYNIAN (LOWER TO MIDDLE TRIASSIC) BRACHIOPODS FROM NORTH DOBROGEA (ROMANIA)

Brachiopods obtained from several Triassic localities in North Dobrogea, in Romania, are described. Upper Spathian and Aegean Hallstatt-type red limestones have been sampled in the Desli Caira section, proposed as the GSSP for the base of the Anisian. The Bithynian brachiopods mostly originate from the Tubiphytes -microbial buildup in the Mahmudia quarry, and also from the Hallstatt-type limestones of Agighiol and Orta Bair. Their age estimates are supported by ammonoids collected from the same beds. The upper Spathian and Aegean assemblages of Desli Caira consist of four rhynchonellids, with one genus and two species newly described, Ortarhynchia petersi gen. n. sp. n. and Austriellula iordanae sp. n. The Bithynian assemblages comprise the most diverse fauna, with 15 species, four species of which are newly described, Ortarhynchia petersi gen. n. sp. n., Piarorhynchella kittli sp. n., Ptychomentzelia dobrogeana sp. n. and P. simionescui sp. n. In the Tubiphytes facies of Mahmudia, the assemblage is numerically dominated by mentzeliids and dielasmatids, forming 84.8 % of the whole assemblage. Spiriferinids and rhynchonellids form the minor component. Instead, rhynchonellids prevail in the Hallstatt facies at Agighiol and Orta Bair. The assemblages described here are hardly comparable with those of the western Tethys. The Bithynian assemblage is very different from its equivalent described from the substage stratotype in Turkey. In North Dobrogea, the carbonate substrate and clear and agitated water supported an assemblage with high diversity. In contrast, in Bithynia, the brachiopod community dwelled on a softer and muddier substrate, with higher density and lower diversity. The locality of Aghdarband (Iran) also delivered Bithynian brachiopods, forming another different assemblage. The recovery and radiation of brachiopods after the P/T crisis is discussed in the framework of Palaeo-Tethyan palaeogeography, making comparisons with the South China localities.

Conodonts from the mid-Carboniferous boundary GSSP at Arrow Canyon, Nevada, USA

The Global Stratotype Section and Point of the mid-Carboniferous boundary was selected in the Arrow Canyon section within the lower Bird Spring Formation at the first evolutionary appearance of the conodont Declinognathodus noduliferus (Ellison and Graves) sensu lato. The studied boundary beds, spanning a 38.8-m interval from the Upper Mississippian into the Lower Pennsylvanian, occur in bryozoan-brachiopod-crinoidal grainstones/packstones with conodonts and foraminifers. The conodonts of the studied interval belong to the shallow-water Adetognathus-Rhachistognathus biofacies. The Adetognathus and Rhachistognathus species/subspecies A. lautus (=A. gigantus), A. spathus, R. minutus minutus, R. muricatus, R. primus, R. prolixus, R. websteri and transitional forms dominate the succession. Gnathodus girtyi simplex, G. lanei n. sp., G. defectus and transitional forms between them are abundant. The elements of the boundary-marker D. noduliferus s. l. and transitional forms between G. girtyi simplex and D. inaequalis are less common. The occurrences of Idiognathoides spp. are very rare. Neognathodus spp. only occur in the upper part of the studied interval. The mid- Carboniferous boundary stratotype has been studied by many workers but its conodonts have been rarely described systematically. The detailed updated descriptions of themost stratigraphically important taxa are given in this paper. The evolution of Gnathodus, Adetognathus and Rhachistognathus species within the mid–Carboniferous interval is discussed. Four lineages are summarized: 1) C. unicornis, A. unicornis, A. lautus and A. spathus; 2) G. girtyi girtyi, G. g. simplex and D. inaequalis; 3) G. lanei and G. defectus; and 4) R. prolixus, R. muricatus and R. websteri/R. primus/R. minutus.