Stratotype Section Research Articles

Results of Paleomagnetic Study of the Neoproterozoic Katav Formation (Southern Urals)

The Neoproterozoic Katav Formation, which is a part of the Ural stratotype section, was considered to be remagnetized in the Late Paleozoic for many years. If the primary magnetization of the rocks is proven, the magnetostratigraphic record found in the Katav Formation may become a good paleomagnetic benchmark in the Neoproterozoic history of the Earth and serve as a source of information about deep processes in the Earth and their evolution. In this work, the arguments in favor of the primacy of the high-temperature characteristic component of magnetization of the Neoproterozoic Katav Formation rocks, previously put forward by V.E. Pavlov and I. Galle, were verified and confirmed on more extensive and detailed material. New paleomagnetic data have been obtained for two sections of the Katav Formation in the Southern Urals near the town of Yuryuzan and the village of Galiakberovo, as well as the overlying Inzer Formation near the village of Galiakberovo. A detailed magnetostratigraphic section of the Katav Formation for the Yuryuzan section is presented. The analysis of the upper part of the section shows 39 polarity intervals within the 74.6 m thick strata. The new data confirmed the existence of a trend of displacement of paleomagnetic directions from bottom to top along the studied sections of the Katav Formation, directed towards the paleomagnetic direction of the overlying Inzer Formation. The total value of the displacement in the Katav Formation is consistent in sections located at a distance from each other, located in areas with slightly different geological history. A significant difference in the direction of the characteristic component of magnetization in the Katav Formation from the corresponding directions in the Inzer Formation was confirmed. Generalization of new and previously obtained data gives grounds to consider the primary characteristic component of magnetization of the Katav Formation deposits, previously considered to be remagnetized. The frequency estimates of the geomagnetic reversals revealed by the new data in the upper part of the Yuryuzan section using the results of our previously performed cyclostratigraphic analysis are 11–12 reversals per million years. Thus, the existence of another interval of geomagnetic field hyperactivity in the Neoproterozoic is confirmed.

A mid-20th century stratigraphical Anthropocene is recognisable in the birth-area of the industrial revolution

The formalisation of the Anthropocene as a subdivision of the Geological Time Scale has been under debate. Its stratigraphic boundary has been proposed as a precise Global boundary Stratotype Section and Point (GSSP) in the mid-20th century, but it is part of an episode of human-induced changes to the Earth System that have unfolded over millennia. Here we attempt to identify stratigraphical patterns of the Anthropocene from a previously well studied lake sedimentary archive from the English Midlands, located in one of the most heavily human-modified landscapes in the UK, and the birthplace of the Industrial Revolution. Our analysis is predicated on the sedimentary succession of Groby Pool, a small lake situated to the immediate northwest of Leicester. We have found that whilst proxy signals for biotic change are indicative of significant landscape and consequent ecological changes prior to the 20th century, the signal from radiogenic fallout and rapid increase in spheroidal carbonaceous particles indicative of fossil-fuel combustion yield a clear mid and later 20th century stratigraphical signature that corresponds with the Great Acceleration of the post-WWII period. We therefore demonstrate clear stratigraphical signatures in the oldest Industrial Revolution landscape on Earth that are consistent with a mid-20th century start point for the Anthropocene.

Orbital and suborbital temperature variability in the central Mediterranean across the Pliocene/Pleistocene transition.

A high-resolution record of central Mediterranean Sea Surface Temperatures (SSTs) based on the alkenone UK'37 index and planktic δ18O values for the surface-dweller G. ruber has been reconstructed across the Pliocene/Pleistocene transition at Monte San Nicola (Sicily), reference area for the GSSP (Global Boundary Stratotype Section and Point) of the Gelasian Stage. Spectral analyses indicate that the SST record is predominantly paced by a cyclicity in the ~47 kyr time domain, consistent with the obliquity driven glacial-interglacial variability that is expected to dominate in the interval of relevance. In addition, two suborbital periodicities in the ~5 kyr and ~8 kyr time domains provide a pervasive spectral signal that proves to be especially strong during the MIS (Marine Isotope Stage) 100 glacial, at the inception of the Northern Hemisphere Glaciation. This high frequency climatic instability, a prominent feature of the early Gelasian, might reflect episodic events of massive disruption of the Atlantic Meridional Overturning Circulation with increased production of cold, low-salinity water masses in the North Atlantic. Alternatively, it may be interpreted as the resonance (i.e., harmonics) of the low-latitude precessional forcing in mid-latitude regions. Although the driving mechanisms of these processes remain largely unconstrained, our study emphasizes the role of the central Mediterranean as the main reference for high-resolution paleoclimatic studies in the Neogene and the Quaternary.

Geological structure and faunistic characteristics of the Mansurovo unique locality of early triassic tetrapods and ichnofossils, Orenburg Region

The geological features of the Mansurovo unique locality of the remains of tetrapods and ichnofossils, Orenburg Region (Gostevskaya Formation, Lower Olenekian Substage, Ustmylian Horizon) are considered. A layer-by-layer description cross-section of 16 ditchs and their correlation with the section construction along the line of ditchs are provided. The Mansurovo section, based on biostratigraphic (Wetlugasaurus malachovi grouping of the Wetlugasaurus Fauna) and lithologic-facies data, correlates with the middle part of the stratotype section of the Gostevskaya Formation (Buzuluk Depression of the East European Platform). The geological features of the locality indicate a heterogeneous structure of the identified four geological units of channel-floodplain genesis within the study area, which correspond to alternating sedimentation cycles. The genesis of deposits was clarified using structural-textural analysis and microlithological analysis of rocks in thin sections. The faunistic complex of tetrapods and macroflora, as well as unique complex of ichnofossils were also characterized. Based on the data of lithological-facial analysis, a sedimentation model of the genesis of the locality is presented, showing the uneven nature of sedimentation pattern due to the wandering of river branches and their periodic drying out in a hot and arid climate during the Early Olenekian. Taking into account paleontological data, taphonomy was analyzed, indicating the burial process in the river setting in strong current condition and the possible death of Temnospondyli in subaquatic conditions.

A Neogene succession in the city centre of Antwerp (Belgium): stratigraphy, palaeontology and geotechnics of the Rubenshuis temporary outcrop

A temporary outcrop near the “Rubenshuis” in the centre of Antwerp (northern Belgium) facilitated the study of the Neogene glauconitic sand of the Berchem and Kattendijk formations, west and south of their respective stratotype sections. In contrast to the latter sections, the exposed Kiel Member of the Berchem Formation contains a relatively silty interval in its upper part, which is also reflected in Cone Penetration Tests. This silty interval is rich in molluscs, including the subspecies Glossus lunulatus cf. lunulatus and Ennucula haesendoncki haesendoncki, previously unknown from this member. Dinoflagellate cysts indicate that the main body of the Kiel Member was deposited during the middle Burdigalian, while only the upper part was deposited during the late Burdigalian. The Kiel Member is covered by the shell-rich, silty sand of the Langhian Antwerpen Member (Berchem Formation). Both members display soft-sediment deformation structures, probably caused by differences in silt content between and within these units. The Antwerpen Member is incised by the Lower Pliocene Kattendijk Formation, which reduced the thickness of the former to only 1.1 m, compared to 7 m in northeastern Antwerp. As a result, the basal gravel of the Kattendijk Formation contains many fossils reworked from the Antwerpen Member, in addition to autochthonous molluscs and Ditrupa. The Zanclean fauna resembles associations known from the highest part of the Kattendijk Formation in the former Oosterweel outcrop north of Antwerp, while it differs from the fauna of the lowermost Kattendijk Formation near Doel and Kallo. Hence, the palaeontological observations corroborate the regional depositional model of this unit, suggesting that only the youngest gully sequence of the Kattendijk Formation was deposited across the city of Antwerp.

Organic walled dinoflagellate cyst biostratigraphy of the Bartonian/Priabonian GSSP Alano di Piave section, NE Italy

The present paper augments the multidisciplinary stratigraphic analysis of the Global Stratotype Section and Point (GSSP) Bartonian-Priabonian boundary Alano di Piave section (NE Italy). Twenty-seven stratigraphically signficant organic walled dinoflagellate cyst events, calibrated against the magnetostratigraphic polarity timescale, and earlier established zonations based on calcareous microfossils are recognized. Among these events the first occurrence (FO) of Oligokolpoma agniniae sp. nov. (∼8 m below the GSSP boundary), and the FO of Reticulatosphaera actinocoronata (∼8 m above the GSSP boundary) may be considered as additional stratigraphic indicators for the Bartonian-Priabonian boundary. Six new potentially stratigraphically significant species Heteraulacacysta alanoensis sp. nov., Heteraulacacysta reticulata sp. nov., Impagidinium bellunoensis sp. nov., Impagidinium veneziaense sp. nov., Lophocysta domenicorioi sp. nov., and Oligokolpoma agniniae sp. nov. are formally described.

THE IMPORTANCE OF FOSSILS AND THEIR COLLECTIONS IN THE DEVELOPMENT OF MODERN STRATIGRAPHY

ABSTRACT The disciplines of palaeontology and stratigraphy are inextricably linked and it is not a surprise that fossils and their collections played and continue to play a major role in recognizing and correlating rock successions. Geological systems have traditionally been identified by their lithologies and fossil content. Collections in state and other recognized institutions are key references to the passage of geological time and organic evolution but are also fundamental for the correlation of rock successions. Stratigraphically-arranged displays, common in the nineteenth and early twentieth centuries have been commonly morphed into galleries show-casing the evolution of life. Nevertheless, chronostratigraphic units, such as systems, series and stages defined on their fossil content ultimately proved an unstable concept. Stages were recognized by the presence of groups of fossils initially in a type area and elsewhere on the occurrence of some or all of those in the type sections. Global Boundary Stratotype Sections and Points (GSSPs) are where rock meets time, at a point defined in a section and provide a more stable way to define and correlate rock successions.

The problem of ammonoid substantiation of the Artinskian–Kungurian boundary in Western Verkhoyanie

Kungurian ammonoids had high taxonomic diversity, but were distinguished by an extremely high level of endemism and sharp geographic differentiation. Therefore, outside the regions containing the most important conodont taxa, the Artinskian-Kungurian boundary based on ammonoids must be established through indirect evidence due to the lack of common species with potential global stratotypes of the lower boundary of the Kungurian. A long-term study of the reference sections of the Echian and Tumarian regional stages and their ammonoids made it possible to change the understanding of the bio- and lithostratigraphy of the Artinskian-Kungurian boundary deposits of the Kuranakh structural-facies zone of Western Verkhoyanie. Clarification of the upper boundary of the Khabakh Formation in the stratotype section led to the fact that the ammonoids previously belonging to this formation began to be considered in the lower part of the Orol formation. They characterize the Paratumaroceras? sp. nov. biostratigraphic beds of the lower part of the Tumarian Regional Stage. At the current level of knowledge, the ammonoid substantiation of the Artinskian–Kungurian boundary in Verkhoyanie is difficult due to the existing hiatus corresponding to the Khabakh formation and its age analogues. However, the appearance at the base of the Tumarian Regional Stage of the first paragastrioceratids with a ventral sinus in transverse sculpture (Paratumaroceras? sp. nov.) suggests that the boundary in question is located near the base of the indicated regional stage or even combined with it. For further clearer identification of the Kungurian lower boundary in Verkhoyanie, new studies of the Echian–Tumarian boundary deposits in typical sections, independent of paleontology, are necessary. Such research should primarily include isotope-stratigraphic subdivision and high-precision U-Pb dating.

Conodont biostratigraphy of the Famennian Makarovian Regional Substage in the Kuk-Karauk section, west slope of the Southern Urals

The Makarovian Regional Substage (Famennian Stage) stratigraphic interval is defined more accurately in the Kuk-Karauk stratotype section (Sikasya River, west slope of the Southern Urals) by conodonts. It is equal to the Pa. minuta minuta, Pa. crepida, Pa. rhomboidea, Pa. marginifera marginifera conodont zones. The absence of intervals equal to the Pa. termini, Pa. glabra prima, Pa. glabra pectinata and Pa. gracilis gracilis zones is testifies to a hiatus. The Pa. crepida and Pa. rhomboidea zones are revealed in the studied section for the first time. Conodont complexes are characterized by rich taxonomic and quantitative diversity (six genera and 48 species). Species of the genus Palmatolepis (up to 92%), which are representatives of deepwater palmatolepid biofacies, predominate.

Calcareous Nannofossil variability controlled by Milankovitch and sub-Milankovitch periodicity in the Monte San Nicola section (Gelasian GSSP / MIS 100–104)

The Quaternary marks the beginning of the ice ages, with the establishment of a stable Northern Hemisphere ice sheet. The Monte San Nicola section, southern Sicily (Italy) is the Global Boundary Stratotype Section and Point of the Gelasian Stage of the Lower Quaternary Subseries and is attracting new attention for providing valuable information on paleoclimate evolution.Here we present a paleoenvironmental reconstruction based on new data from calcareous nannoplankton, the phytoplankton organisms that are sensitive to sea surface changes and water column dynamics. We adopt statistical and signal analysis to support our paleoenvironmental model. The most evident paleoenvironmental signal throughout the investigated interval is the contrast between the abundance patterns of placoliths and Florisphaera profunda, the former pointing to surface productivity (water column mixing, shallow nutricline), the latter to the establishment of a deep nutricline. The observed nutricline depth shift occurred with a regular precessional pace, following Northern Hemisphere summer insolation and, likely, North African monsoon activity. A significant periodicity of 8 kyr, in tune with late Quaternary Heinrich events, is also observed in nannoplankton taxa, supporting previous findings on the existence of suborbital climatic variability even at the Pliocene-Pleistocene transition.

Stable carbon isotope chemostratigraphy of the base of the Callovian in Greenland

D’Orbigny named the Callovian stage after Kellaways in Wiltshire, UK, in the 1850 s. However, agreement on its boundaries and, more recently, on the position and location of the Global Boundary Stratotype Section and Point (GSSP) for the base of the Callovian has proven difficult for the last 170 years. This is mainly due to the lack of agreement on the appropriate index fossil and its regional and global correlations, as well as the location of the stratotype section. Stable carbon isotope chemostratigraphy and event stratigraphy are now essential tools for aiding in the definition of GSSPs. In this study, stable carbon isotopic analysis of 91 samples from east Greenland’s Middle Jurassic shallow marine sandstones of the Pelion Formation (Store Koldewey and Hold with Hope) and correlative and well-dated offshore siltstones and mudstones of the Fossilbjerget Formation (Jameson Land) is used to discriminate several isotopic events previously observed in other European basins and propose the early Callovian (δ13CTOC) positive carbon isotopic excursion as a secondary marker for defining the Callovian GSSP. The early Callovian (δ13CTOC) positive carbon isotopic excursion is a fundamental tool for superregional correlation between candidate GSSPs and Standard Auxiliary Boundary Stratotypes. It can also help establish a chronological order (synchronous vs diachronous) of species occurrences between different locations.

Late Quaternary history of the Kerch Strait — the stratotype region for the Black Sea

The Kerch Strait has periodically connected to the Black, Azov, and Caspian seas throughout its Late Quaternary history. The strait's deposits reflect the changes in the natural environment of the entire Ponto-Caspian region, which are a response to global climate change. Several studies have been done on the region's stratigraphy, biostratigraphy, geomorphology, and paleogeography. However, most of the current knowledge about the paleogeography of the area is based on the analysis of empirical data collected more than 25 years ago, and due to the lack of detailed geochronological studies, many palaeogeographical problems remain unresolved.This paper presents a reconstruction of environmental change in the Kerch Strait during the Late Quaternary. The reconstruction is based on the results of a comprehensive study of the sedimentary sequences in the Kerch Strait carried out by the author and colleagues over the past ten years. The study examines the deposits of two stratotype sections of the Karangatian (Eemian) transgression and the four boreholes’ sections in Tuzla Island in the central part of the strait.A biostratigraphic division of the Upper Quaternary deposits of the Kerch Strait was carried out based on a malacofaunal study. Mollusc assemblages corresponding to various paleogeographic stages of development were identified, and their paleoecological characteristics were described. Luminescence and radiocarbon ages made it possible to determine the time intervals of established paleogeographic stages in the strait's history. Detailed luminescence dating of the Karangatian transgression sediments of the Eltigen and Tuzla stratotype sections has been carried out for the first time.Six main stages in the Kerch Strait natural environment development were established in the Late Quaternary and correlated with global and regional climatic events: Karangatian, with three stages (MIS 5e-c); Tarkhankutian (MIS 5a); Post-Karangatian (MIS 4); Surozh (MIS 3); Neoeuxinian, with two stages (MIS 2); and Chernomorian (MIS 1). Two episodes of the Caspian waters flowing through the Kerch Strait into the Black Sea were identified in MIS 5c and at the end of MIS 2.

Cyclostratigraphy of late Cambrian marine sedimentary records and reconstruction of Earth-Moon system parameters

The Cambrian period is an important era in geological history, marked by numerous major geological and biological events. To better understand these events, it is important to establish a high-precision chronostratigraphic framework. An astronomical time scale can be created by the identified Milankovitch cycles in well-preserved stratigraphic successions. Duibian B section in Jiangshan (Zhejiang Province, China) is the global stratotype section and point (GSSP) for the Jiangshanian Stage, and this section provides well-preserved records covering the upper Paibian to lower Jiangshanian stages. In this study, we use high-resolution magnetic susceptibility record to conduct cyclostratigraphic analysis of the Duibian B section. Our results indicate that the 2.44 m, 0.84–0.73 m, 0.20–0.19 m, and 0.12–0.09 m sedimentary cycles may represent long-eccentricity, short-eccentricity, obliquity, and precession cycles, respectively. Using the stable 405-kyr eccentricity cycles, we constructed an ∼5.96 Myr floating astronomical time scale to calibrate agnostoid trilobite zones. In addition, we reconstructed the precession rate k from geological records, and our result provides an insight into the Earth-Moon distance and length of day in the late Cambrian (Paibian–Jiangshanian, ∼494.2 Ma). It enriches our understanding of the Earth-Moon evolutionary history in deep time.

Calcareous nannofossil biostratigraphy, bioevents, and palaeoecological interpretation of the lower-middle Miocene outcrops in west central Sinai (Egypt)

The Burdigalian/Langhian (B/L) boundary has not yet been designated as a Global Stratotype Section and Point (GSSP), despite various proposed zonal schemes. In the Gulf of Suez region of Egypt, the Burdigalian-Langhian successions are notable for hosting significant hydrocarbon reservoirs within a tectonic rift setting. Therefore, biostatigraphy plays a crucial role in exploration endeavors in this area. The nannofossil biostratigraphy is investigated in two sections, Wadi Baba and Wadi Gharandel, of the lower-middle Miocene from west-central Sinai. Three biozones, NN3 (Sphenolithus belemnos) Zone, NN4 (Helicosphaera ampliaperta) Zone, and NN5 (Sphenolithus heteromorphus) Zone, are identified from the studied interval. The NN4 Zone could be divided into MNN4a/b and MNN4c. Important biovents are discussed, such as the S. heteromorphus paracme interval and the first occurrence and evolution of the Discoaster exilis and Discoaster variabilis groups. Based on the cluster analysis, the recorded taxa can be subdivided into four groups that reflect their palaeoclimatic preferences. The paleoecological interpretation of the studied Rudies Formation indicates prevailing cool and eutrophic nutrient conditions based on the dominance of taxa such as Coccolithus pelagicus, Reticulofenestra minuta, and Cyclicargolithus floridanus. The nannofossil taxa responses to sea level curve are interpreted. Fluctuations in taxa abundance and diversity indicate a slight rise in the sea level at the base of the Burdigalian followed by sudden drop in the sea level at the middle Burdigalian. High sea-level conditions prevailed again until the B/L boundary. During the Langhian period, many small-scale fluctuations in sea-level curve are detected.

Palaeoenvironmental and palaeoclimatic study of the Olazagutia (Spain) and Ten Mile Creek-Arbor Park (USA) sections during the Coniacian–Santonian interval

The mechanisms and palaeoenvironmental conditions leading to and occurring through the Coniacian–Santonian Ocean Anoxic Event 3 (OAE3) are poorly known, particularly with regard to the marine phosphorus cycle and the climatic conditions in general. To explore these issues further, two famous locations have been studied, Olazagutia (Spain) and Ten Mile Creek–Arbor Park (TX, USA), which are located in different palaeogeographical areas and deposited at different palaeodepths. The study of these two locations is based on mineralogy (bulk and clay), geochemistry (stable isotopes, organic matter, phosphorus and major element) and high-resolution biostratigraphy (nannofossils) to infer changes in climate and primary productivity across OAE3. The investigated sections were both previously proposed as candidates for the base Santonian global boundary stratotype section and point (GSSP). The Olazagutia section was ratified in 2013, where the base of the Santonian was defined by the first appearance datum of the inoceramid Platyceramus undulatoplicatus . Both sections, deposited in oxygenated conditions, record the δ 13 C patterns which characterized the Coniacian–Santonian OAE3 interval, in particular the positive carbon-isotope excursions comprising the K2, Michel Dean and Bedwell events. New nannofossil biostratigraphy for both sections is presented including new occurrences. Significant diachronism of marker taxa is observed between the Spanish and Texan sections. Based on a weathering index and mineralogy, similar climate changes are observed in all sections. The climate shifted synchronously from relatively drier to warmer and wetter conditions above the Coniacian–Santonian boundary from the Michel Dean event to above the Bedwell event during the early Santonian. Fluctuations in total phosphorus contents appear mainly to have been driven by changes in detrital input and consequently by climate change in Spain and Texas. Several bentonite layers were observed in Texas close to the Coniacian–Santonian boundary, but only one located 7 m above the Coniacian–Santonian boundary provided sufficient well-preserved zircon minerals, and gives an age of 86.24 ± 0.12 Ma based on U–Pb geochronology, consistent with an early Santonian age.

Carbonate-siliciclastic deposits of the Lower Uk Subformation (Neoproterozoic) in the stratotype section and its correlation within Bashkirian Mega-Anticlinorium of the Southern Urals

Research subject. Carbonate-siliciclastic deposits of the Lower Uk Subformation were thoroughly studied in the section along the Yuryuzan river (near Ust-Katav town, Chelyabinsk region) and correlated with subformation sections along the Basu, Zilim and Bolshoy Inzer rivers. Material and methods. A detailed description of the stratotype section was carried out; sandstones, siltstones and limestones were studied in thin sections. The sections were correlated with each other. Results. Relationships between the Lower Uk Subformation and the underlying deposits are studied. The petrographic characteristics of rocks are presented. The Lower Uk Subformation sequences are traced between sections of various structural-tectonic zones of the Bashkirian Mega-anticlinorium (BMA). Conclusions. The set of features supports the idea about the presence of a sedimentary hiatus at the base of the formation, even in the most complete sequences (which contain the locally developed Shubino Member of the Minyar Formation). In the stratotype and in other reference sections, the Lower Uk Subformation has a pronounced three-membered structure; it is subdivided into the lower (siliciclastic) Yamashta, middle (substantially carbonate) Akkostyak, and upper (siliciclastic-carbonate) Avdyrdak members. The lithofacies analysis results suggest a change in environments from coastal-marine siliciclastic to shallow-marine siliciclastic-carbonate (middle and inner ramps) due to fluctuations in the relative sea level and, probably, climate change. It was established that the area of the Suleimanovo anticline at latest Riphean corresponded to the distal sedimentary environments in comparison with the southern and western zones (Alatau anticlinorium) of the BMA.

Lithogeochemical characteristics and sedimentary environments of the Uk Formation limestones (upper Riphean, Southern Urals)

The lithogeochemical characteristics of the Uk Formation limestones (Uppermost Unit of the Riphean stratotype section in the Southern Urals) are considered. Data points of limestones (40 samples) accumulated in the middle and inner ramp environments have a quite contrasting distribution on diagrams with parameters (La/Sm)sh, (La/Yb)sh and (Sm/Yb)sh, proposed based on the systematization of a significant amount of analytical data on carbonate sequences formed in various platetectonic (in the broad sense of the word, paleogeographic) environments (according to [Zhang et al., 2017]) was established. The data points of the limestones of the Medved Member of the Uk Formation, which was formed, according to a detailed lithological-facies analysis, in the middle ramp environment, in the indicated diagrams located towards the field of limestones of the open ocean, while the limestones of the Manaysu Member (inner ramp deposits) in their geochemical characteristics are more consistent with the limestones of the near-coastal environments. Thus, the geochemical characteristics of the Uk Formation limestones seem to confirm the conclusions of the previous reconstructions. It has been suggested that in the example we described, the distribution of trace elements in the inner ramp limestones was apparently controlled by fine-grained siliciclastic material coming from the continent, while in the geochemical features of deeper-sea middle ramp limestones the influence of the open ocean environment is already perceptible.

Jurassic–Cretaceous boundary in the Dedina section (Serbian Carpathians): Effects of remagnetization on magnetostratigraphy

The Upper Tithonian to Lower Berriasian carbonate sequence of the Getic Nappe system was studied near Golubac (eastern Serbia) using rock-magnetic and paleomagnetic methods to verify the age of the magnetization and to correlate magnetostratigraphy with biostratigraphy. A major part of the Dedina section shows the presence of authigenic goethite, hematite and magnetite as carriers of remagnetization. The youngest overprint, residing in goethite, sometimes carrying up to 90 % of natural remanent magnetization, was probably received after 18 Ma. The remagnetization residing in hematite and magnetite, attributed to the late Early Cretaceous collision, was obtained during long normal polarity Chron C34 (118–82 Ma). The mean direction implies a clockwise post-remagnetization rotation by about 57°. The normal (Dn) and reverse (Er) polarity components, heavily affected by the chemo-remanent magnetization overprint, can be tentatively interpreted in terms of polarity zones. Thus, the obtained data enabled a preliminary identification of M17r to M19n.2n magnetochrons. The correlation of magnetostratigraphy with biostratigraphy of the Dedina section contributes to the stratigraphic framework necessary for the definition of the Berriasian Global Boundary Stratotype Section and Point.

Sedimentary DNA reveals phytoplankton diversity loss in a deep maar lake during the Anthropocene

AbstractAnthropogenic‐driven environmental change, including current climate warming, has influenced lake ecosystems globally during the Anthropocene. Phytoplankton are important indicators of environmental changes in lakes and play a fundamental role in maintaining the functioning and stability of these ecosystems. However, the extent to which lake phytoplankton were affected by anthropogenic or climatic forces during the Anthropocene remains unclear. Here, we investigated the 160‐yr‐long dynamics of the phytoplankton community (cyanobacteria and eukaryotic microalgae) in response to anthropogenic forcing in Sihailongwan Maar Lake—a candidate for a Global boundary Stratotype Section and Point for demarcation of the Anthropocene—using DNA metabarcoding and traditional paleolimnological approaches. Our results show a significant decline in phytoplankton diversity and an abrupt shift in community composition around the 1950s, corresponding to the beginning of the “Great Acceleration” period. Specifically, phytoplankton taxa coexistence patterns, niche differentiation, and assembly mechanisms changed significantly after the 1950s. Overall, increases in air temperature and anthropogenic forcing appear to be the dominant controls for community reorganization and diversity decline of the phytoplankton from this deep maar lake. A neutral community model suggests that phytoplankton community composition was mainly controlled by stochastic processes before the 1950s; however, as time progressed, deterministic effects driven by anthropogenic global warming increased. The results of this study imply that anthropogenic perturbations have led to a loss of phytoplankton diversity and a further decline in ecological resilience in deep lakes, with likely knock‐on effects on the productivity and function of lake ecosystems.

A Hyperactive Geomagnetic Field in the Late Visean (Early Carboniferous) From the Late Asbian Stratotype Section in Northwest England, UK

Plain Language SummaryNearly synchronous global changes in geomagnetic polarity give both a detailed irregular pacing to geological time and provide a glimpse into heat transfer processes across the core—mantle boundary which drives the Earth's geodynamo. Although the Late Carboniferous is characterized by some well‐studied reversals, details of the tempo of polarity changes in the Early Carboniferous are unknown. This work addresses this by providing a detailed record of polarity changes over a ∼2 million year interval at around 334.5–332.5 million years ago‐from the Trowbarrow Quarry section in NW England. We demonstrate that these limestones likely preserve magnetization from close to their time of formation and record at least 31 polarity reversals. These observations support the idea that the Earth's dynamo was in a hyperactive reversing state similar to those sustained for tens of Myr in the Late Jurassic, parts of the Cambrian and the Late Ediacaran. It further corroborates a ∼200 Myr cyclicity in paleomagnetic field behavior since the Precambrian, potentially linked to variable core heat flow forced by mantle convection.