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[Display omitted] • VMS-hosted felsic volcanic rocks and marine limestones were formed contemporarily. • Chemostratigraphy of limestones and zircon U-Pb dating reveal their early Cambrian age. • VMS-hosted volcanic rocks were produced by high degree partial melting of juvenile lower crust. • VMS-hosted rocks were formed in the back-arc setting where the marine transgression occurred. The Salair terrane located in the northern part of the Central Asian Orogenic Belt (CAOB) contains many epithermal deposits including volcanogenic massive sulphide (VMS) deposits. The host rocks mainly consist of felsic volcanic rocks such as lavas, volcanic breccias and tuffs that associated with thick strata of carbonates. In this study, we present zircon U–Pb ages, whole rock geochemistry, and Nd isotope data from the volcanic rocks, and results of geochemical and isotope (Sr, C, O) studies of carbonates to constrain their age and petrogenesis, and to characterize the tectonic setting. Zircon U–Pb dating reveals that the ore-bearing felsic lavas have age of 519.3 ± 1.9 Ma, while the felsic tuffs have age of 516.0 ± 0.9 Ma. These volcanic rocks are characterized by high SiO 2 and Na 2 O contents, enrichment in light rare-earth elements, remarkable negative Eu anomalies, and pronounced depletion in Nb, Ta, P, and Ti. They have depleted ɛNd(t) values ranging from +4.9 to +6.3, and young two-stage Nd model ages (from 0.82 to 0.64 Ga). The felsic volcanic rocks from the Salair terrane are interpreted as highly evolved I-type magmatic rocks that might be produced by high degree partial melting of juvenile lower crust without a significant contribution of ancient crust and without crustal reworking. Felsic volcanism was accompanied by the formation of thick strata of carbonates. These carbonates are marine limestones with Mg/Ca ratios less than 0.007, δ18O (SMOW) values from 17.1 to 23.8 ‰ and δ13C (PDB) values between –0.9 and +0.9. Their Sr isotope composition varies in a narrow range within 0.70844–0.70859 that interpreted as representing proxy for coeval seawater. These values are consistent with depositional ages of 520–510 Ma and confirms the synchronicity of the formation of carbonates and felsic volcanism. Based on the regional geology and geochemistry, the ore-host rocks of the Salair terrane were formed in the back-arc setting where the marine transgression occurred as a result of graben subsidence. It is important for better understanding epithermal deposits in the northern CAOB and might provide new insights about prospecting the VMS deposits in similar tectonic settings. [ABSTRACT FROM AUTHOR]

Throughout the Latest Triassic and the Early Jurassic, major changes in paleogeography, climate and eustatic sea-level impacted on the development of shelf depositional environments. Secular trends in environmental conditions were punctuated by transient perturbations that occurred in relation to large-scale volcanic events, such as the emplacement of the Central Atlantic Magmatic Province at the Triassic/Jurassic boundary and the Karoo–Ferrar Large Igneous Province in the early Toarcian. We here present bulk organic (HAWK programmed pyrolysis) and organic carbon isotope (δ13Corg) data for three drill cores recovering Latest Triassic and Early Jurassic strata (Rhaetian to Toarcian). Study sites are located in the northeastern part of the Central European Epicontinental Sea and were positioned along a distal–proximal transect of the North German Basin. This allows discussing the differential response of depositional settings and organo-facies toward secular and transient environmental change. Biostratigraphically anchored trends in δ13Corg values allow the precise correlation along the transect, as well as with distant sites. At all North German locations, diagnostic secular trends in δ13Corg are punctuated by transient negative carbon isotope excursions, reflecting perturbations of the global carbon cycle at the Triassic/Jurassic boundary and in the early Toarcian. Stratigraphic gaps occurred during sea-level lowstands and are most pronounced at shallow proximal sites. Programmed pyrolysis data indicate spatiotemporal organo-facies trends that on a temporal scale occurred in response to sea-level and climate trends, while spatial patterns were governed by basin morphology and paleobathymetry. Substantial marine organic matter accumulations occurred at high sea level during the Toarcian only, and were most continuous at distal sites. [ABSTRACT FROM AUTHOR]

Over the past few decades, Toarcian (Early Jurassic) black shale deposits of NW Europe have been extensively studied, and the possible global and regional mechanisms for their regional variation have been discussed. In this context, the black shales of the Northwest German Basin are still sparsely studied with regard to their palaeo-depositional history. This study aims to understand the connection between regional and global influences on the widespread Early Toarcian oceanic anoxic event by examining two wells covering the Upper Pliensbachian to Upper Toarcian sediments in the Northwestern German Basin. The core intervals were analysed using a multidisciplinary approach, including geochemistry, biostratigraphy and organic petrography. Marine palaeoenvironmental changes were reconstructed, and sediment sequences were stratigraphically classified to allow a supra-regional stratigraphic correlation. The results reveal complex interactions between sea level changes, climate warming, basin confinement, and Tethys–Arctic connectivity resulting in the Toarcian black shale deposition. Upper Pliensbachian sediments were deposited under terrigenous influence, shallow water depths, and predominantly oxic bottom water conditions. The deposition of black shale is characterized by algal organic material input and anoxic bottom water conditions. Strong correlations between water stratification, anoxia, and bioproductivity suggest that global warming and intensification of monsoonal rainfall, continental weathering, and increasing freshwater and nutrient inputs were the main factors controlling the formation of black shales. Prolonged deposition of OM-rich sediments in the NWGB may be related to intensified monsoonal precipitation in northern Europe and enhanced Tethys–Arctic connectivity at the serpentinum–bifrons transition. [ABSTRACT FROM AUTHOR]

Changes in the values of δ13Соrg in the lower part of the Permian deposits, obtained in the Kuba-lakh Section of the lower reaches of the Lena River and integrated with biostratigraphic data are detected in northeastern Russia for the first time. A comparison with isotope-carbon trends identified in the Asselian and Sakmarian stages of the Southern Urals is proposed. Based on the established sequence of negative shifts of the carbon isotope composition of organic matter, a conclusion is made that the Carboniferous–Permian boundary in the Kubalakh Section is located at the 80 m thick gap in section. The first data independent of the biostratigraphic and paleontological records are obtained on the Late Asselian age of the Tuora-Sis Formation beds containing the Bulunites ammonoid association, the stage assignment of which has been debated for many decades. The chronostratigraphic indefinite interval between the Asselian and Samarian stages is significantly reduced to the upper parts of the Jakutoproductus lenensis Beds. The data obtained indicate that the continuation of the work on the chemostratigraphy of stable carbon isotopes has good prospects for substantiating the division into stages and the interregional correlation of the Lower Permian deposits in Verkhoyanie. [ABSTRACT FROM AUTHOR]

Ferromanganese nodules are important marine storehouses for critical metals and windows for changing oceans. Although advanced in situ analytical techniques have been applied to visualize the elemental distribution in the nodule cross‐sections, their spatial distribution remains largely uncertain. This study addresses this gap by employing micro X‐ray fluorescence mapping of parallel nodule cross‐sections to delineate the spatial distributions of critical metals (Mn, Fe, Co, Ti, Ni, and Cu) in three Co‐rich ferromanganese nodules from the northwestern Pacific Ocean. The 10‐layer Os isotopic compositions of one nodule closely align with the well‐documented marine Os isotope evolution of seawater, providing a chronological framework and a maximum age of ∼36 Ma for these nodules. Three concentric chemostratigraphic layers, labeled L1, L2, and L3, were identified from the inside out, based on microscopic structures and the distributions of critical metals. The early growth stage was marked by Mn‐rich, Si‐rich, and high Mn/Fe ratios, suggesting a diagenetic‐driven process attributed to high paleoproductivity conditions because of the low latitude of the study area at that time. The subsequent growth stages are all hydrogenetic in origin to be rich in Fe, Co, and Ti with low Mn/Fe ratios. The apparent detritus present during the second growth stage of the nodules may correspond to the stronger bottom currents in the early Miocene. The final mineralization stage indicates a more stable environment with diminished bottom current activity, leading to the formation of a dense, laminar hydrogenetic layer. Plain Language Summary: The present study bridges the knowledge gap on the spatial distribution of critical metals through the innovative use of micro X‐ray fluorescence mapping on parallel sections of three nodules in the northwestern Pacific Ocean. Os isotope stratigraphy establishes a chronological framework and a maximum age of ∼36 Ma for these nodules. Distinct concentric chemostratigraphic layers, labeled L1, L2, and L3, have been identified in these nodules. The early growth stage of the nodules is characterized by Mn‐rich, Si‐rich and high Mn/Fe ratios, indicative of a diagenetic‐driven process under high paleoproductivity conditions due to the low historical latitude. The subsequent stages are all hydrogenetic in origin to be rich in Fe, Co, and Ti with low Mn/Fe ratios. The apparent detritus present during the second growth stage of the nodules may correspond to the stronger bottom currents in the early Miocene. The final mineralization stage suggested a period of environmental stability with reduced current activity, forming of a hydrogenetic layer enriched in Fe, Co, and Ti. This study not only enhances our understanding of the complex processes that govern the formation and evolution of ferromanganese nodules but also provides deeper insight into the historical shifts within our oceans. Key Points: Ferromanganese nodule was dated via Os isotope stratigraphy and has a maximum age of ∼36 MaMulti‐element integrated maps were produced to assist in obtaining clearer chemostratigraphy images of ferromanganese nodulesSpatial distribution of critical metals and chemostratigraphy in ferromanganese nodules were visualized via multiple parallel cross‐sections [ABSTRACT FROM AUTHOR]

[Display omitted] • A high-resolution δ13C carb record for the Toarcian of Kuwait is presented. • Negative δ13C carb excursion indicate early Toarcian carbon cycle perturbations. • Major depositional sequences were linked to orbitally-forced sea-level cycles. The Early and Middle Jurassic Marrat Formation in Kuwait was deposited along the southwestern margin of the Neo-Tethys Ocean. The formation has been extensively cored and sampled in deep wells by Kuwait Oil Company for sedimentological and biostratigraphic analyses. Based on mainly long-ranging benthic species, the Middle Marrat Member is assigned in published articles to the Toarcian Stage. The formation has also been sampled for stable carbon and oxygen isotopic analyses in 19 wells across a depositional profile extending from sabkha to intrashelf basin. Stable carbon isotope analyses from these wells (∼2000 samples) reveal the signature of the negative Pliensbachian-Toarcian carbon-isotope excursion (Pl-T-CIE) in the uppermost part of the Lower Marrat Member. The younger early Toarcian carbon-isotope excursion (T-CIE) is recognized in the lower part of the Middle Marrat Member. A composite δ13C carb curve spanning the Middle Marrat Member is constructed by combining overlapping δ13C segments from six wells guided by correlations of regional sequence boundaries and gamma-ray logs. Cyclostratigraphic analyses of gamma-ray logs in these six wells reveal a periodic signal formed by multiples of the 0.405-Ma long-eccentricity cycle. This result suggests the Middle Marrat Member in Kuwait may represent the complete Toarcian Stage consisting of depositional sequences controlled by sea-level cycles with durations ranging between 0.8 and 1.6 Ma. Correlations of the Toarcian succession between Kuwait, Saudi Arabia and Oman are hampered by imprecise biostratigraphic control. This limitation is bypassed by correlating the T-CIE in Kuwait to published δ13C records in the Marrat Formation in central Saudi Arabia and the Mafraq Formation in Wadi Sahtan in Oman. The correlations indicate that whereas the Toarcian Stage is apparently complete in Kuwait, most of the middle and upper Toarcian and the Aalenian are absent in Oman and Saudi Arabia. [ABSTRACT FROM AUTHOR]

The timescales over which fractional crystallization and recharge work in mafic volcano-plutonic provinces is subject to great uncertainty. Currently modeled processes are subject to the scale of measurement: monogenetic basaltic fields accumulate over hundreds of thousands of years, consistent with U-Th-Ra isotopic variations that imply 50% crystallization of basic magmas on timescales of 100,000 years or more, whereas crystal diffusion modeling implies phenocryst residence times of ∼1–1000 years. Monogenetic basalts of the Snake River Plain in southern Idaho, USA, are up to 2 km thick and postdate passage over the Yellow-stone–Snake River Plain hotspot. Detailed lithologic and geophysical logging of core from deep drill holes, along with chemical stratigraphy and high-resolution paleomagnetic inclination measurements, document individual eruptive units, compound lava flows, and basaltic flow groups that accumulated over 1–6 m.y. Hiatuses are commonly marked by loess or fluvial interbeds that vary from ∼0.1 m thick to 20 m thick. Radio-metric (40Ar-39Ar, detrital zircon U-Pb) and paleomagnetic timescale ages show that the deepest hole (Kimama drill hole, 1912 m total depth) accumulated over ∼6 m.y. Cycles of fractional crystallization and recharge are recognized in the chemical stratigraphy as up-section shifts in major and trace elements; these fractionation cycles commonly represent 40%–50% fractionation. Individual fractionation cycles may comprise 20–40 eruptive units (8–17 lava flows) with little to no change in paleomagnetic inclination (0°– 1°), whereas adjacent cycles may differ by several degrees from one another or reflect changes in polarity. Rates of paleosecular variation in Holocene lavas and sediments dated using 14C document significant shifts in magnetic inclination over short timescales, ranging from ∼0.05° to 2°/decade, with an average of ∼0.5°/decade and a minimum rate of 0.05°/ decade. This implies that fractionation cycles with ≤1° variation in magnetic inclination formed on timescales of a few decades up to a few centuries (20–200 years). Thus, the lavas collectively represent only a few thousand years of eruptive activity, with major flow groups separated in time by tens to hundreds of thousands of years. We suggest that the rates defined by paleosecular variation capture the timescales of magmatic chamber evolution (fractionation/recharge) in the seismically imaged mid-crustal sill complex; in contrast, we suggest that crystal diffusion modeling captures the residence times in shallow subvolcanic magmatic chambers that underlie individual monogenetic volcanoes. [ABSTRACT FROM AUTHOR]

The Great Oxidation Event (GOE) during the early Paleoproterozoic represents the first significant buildup in Earth's atmospheric oxygen and resulted in a series of significant changes in the Earth's surface environment. Among them is the 2.22 (or 2.33)–2.06 Ga Lomagundi-Jatuli Event (LJE), which is globally, the largest magnitude and longest duration, marine carbonate positive carbon isotope excursion (δ13CV-PDB>10‰) known. This event has attracted the attention of scholars all over the world. However, except for a high positive carbon isotope excursion (δ13CV-PDB>10‰) recently identified from marine carbonate rocks within the Daposhan Formation in the lower Fanhe Group (or the Sanchazi Group) in the Longgang Block in the northeast North China Craton (NCC), Paleoproterozoic carbonates in the NCC are characterized by a low-amplitude positive carbon isotope excursion (δ13CV-PDB<5‰). This feature is significantly different from the high positive carbon isotope excursion characteristics of carbonates deposited during the LJE period in other cratons. To determine whether there are large-scale and reliable sedimentary records of the LJE in the NCC and the reasons for the low positive δ13C excursion of the Paleoproterozoic carbonates obtained by the previous studies, we conducted field investigations, carbon-oxygen isotopes, and whole-rock major and trace element geochemical analyses of Liaohe Group carbonate rocks from the Anshan area in the northwestern margin of the Jiao-Liao-Ji Belt in the northeast NCC. Our results show that the Gaojiayu Formation of the Liaohe Group in the Anshan area has high positive δ13CV-PDB values from 8.6‰ to 12.4‰ and δ18OV-SMOW values of 17.9‰–27.4‰ (δ18OV-PDB values ranging from −12.6‰ to −3.4‰). This provides solid evidence for the preservation of reliable sedimentary records of the LJE in the northeastern NCC. Deposition of the high positive δ13C excursion (>10‰) of marine carbonate rocks occurred at about 2.15 Ga. Lithological comparisons of different sections and whole-rock geochemical results show that the high positive δ13C excursion is mainly controlled by the stratigraphic interval and depositional ages; the changes of sedimentary facies and diagenesis have no significant effects on reducing of the δ13C values. The intrusion of mafic sills into carbonates has resulted in synchronous decrease of C–O isotopes near the contact zones, but the decreasing amplitude of δ13C is less than 3‰. Therefore, our study firstly identified marine carbonates with high positive δ13C excursion (>10‰) from the Gaojiayu Formation, which provides robust evidence for global correlation of the LJE, which has implications for its genesis and global significance. Moreover, due to global near-synchronization of the LJE, the carbon-oxygen isotope chemical stratigraphy of carbonate rocks deposited during the LJE period, combined with geochronological data, can provide new constraints on the stratigraphic subdivision and correlations of Paleoproterozoic sedimentary successions in the NCC. [ABSTRACT FROM AUTHOR]

The Jurassic–Cretaceous boundary is the only Phanerozoic period-level boundary that lacks a golden spike on the geological timescale despite significant global geological and environmental change during this time related to the opening of the Atlantic Ocean. Paleoenvironmental proxy profiles (total organic carbon, δ34S, δ15N, Fe, Mn, Ce/Ce*, Th/U, δ13Corg, P, Ni, Zn, Cu, and B/Ga) for core 3 of the Baccalieu I-78 well in the Flemish Pass Basin, offshore eastern Canada, exhibit a geochemical anomaly between 3288.5 and 3289 m, overlapping with the biostratigraphic placement of the Jurassic–Cretaceous boundary. Collectively the geochemical analyses are interpreted to indicate that the anomaly is associated with a fall in relative sea level, followed by a rise, which led to restricted circulation, stratification, and widespread anoxia. This anoxia, coupled with an arid climate, further resulted in reduced weathering, limited nutrient supply, and an overall reduction in primary productivity. The results of this study, in conjunction with previous biostratigraphic studies on core 3, suggest that the Jurassic–Cretaceous boundary in Baccalieu I-78 likely falls within the geochemical anomaly, specifically between 3228.5 and 3288.85 m. Furthermore, the paleoenvironmental interpretations derived in this study agree with published reports on global sea level and climate trends around the Jurassic–Cretaceous boundary, implying the influence of global, rather than regional, factors on deposition. This suggests that geochemical proxies may be useful in providing additional paleoenvironmental insights and helping to constrain stratigraphic boundaries, particularly in intervals that lack significant lithological or biological change. [ABSTRACT FROM AUTHOR]

Earth scientists have leveraged carbon isotope records to interpret Earth history and establish chronostratigraphic frameworks for decades (e.g., Halverson et al., 2005, https://doi.org/10.1130/b25630.1; Kaufman & Knoll, 1995, https://doi.org/10.1016/0301‐9268(94)00070‐8; Knoll et al., 1986, https://doi.org/10.1038/321832a0; Saltzman & Thomas, 2012, https://doi.org/10.1016/b978‐0‐444‐59425‐9.00011‐1; Scholle & Arthur, 1980, https://doi.org/10.1306/2f91892d‐16ce‐11d7‐8645000102c1865d). Increasingly detailed and nuanced approaches have been applied to understanding carbon isotope records in light of local‐ and regional‐scale processes that complicate interpretations. The recent work of Gazdewich et al. (2024, https://doi.org/10.1029/2023gc011376) is a prescient example, in which they conduct a series of analyses to constrain the influence of authigenic carbonate burial on the global carbon isotope mass balance during the Late Devonian. Here, I briefly review some recent developments in quantitative approaches to understanding carbon isotope values measured from carbonate rocks (δ13Ccarb), with a focus on comparisons of measured δ13Ccarb values, models for understanding what controls δ13Ccarb values, and correlation tools for aligning δ13Ccarb stratigraphies. These new approaches are elucidating carbon isotope records across Earth history and may prove to be transformative for our understanding of the global carbon cycle. Plain Language Summary: The ratio of stable carbon isotopes measured in carbonate rocks (δ13Ccarb) has long been used as a tool for geologists to estimate the relative ages of ancient rocks by matching trends in δ13Ccarb between localities. Recent work has demonstrated that biological and geological processes at local and regional scales can influence δ13Ccarb, making the matching between localities more complicated. Because of this, increasingly detailed and nuanced approaches have been developed to understand trends in δ13Ccarb. Gazdewich et al. (2024, https://doi.org/10.1029/2023gc011376) recently provided a new protocol for constraining the degree to which one of these geological processes–the burial of in situ‐forming carbonate minerals (authigenic carbonate)–impacted δ13Ccarb values during the Late Devonian (382.7–358.9 million years ago). In this commentary, I provide context for this advancement, highlighting other recent developments in quantitative approaches for understanding δ13Ccarb values. These new approaches have the potential to significantly improve our understanding of the global carbon cycle through time, as inferred by changes in δ13Ccarb across Earth history. Key Points: Quantitative and nuanced approaches are revealing the impact of local‐ and regional‐scale processes on δ13Ccarb values and correlationDespite complications, δ13Ccarb correlation still appears to often yield realistic chronostratigraphic frameworks across Earth historyA full accounting of the uncertainties associated δ13Ccarb values is needed for future interpretations, and to improve our understanding of the global carbon cycle across Earth history [ABSTRACT FROM AUTHOR]

Introduction: The Yucca Formation is a Lower Cretaceous sedimentary unit present in West Texas. Based on its relative stratigraphic position in the Cretaceous succession of West Texas, it is expected that the Yucca Formation is of Albian and/or Aptian age. It is also expected that the carbon isotope excursions associated with OAE 1a and OAE 1b should be identified in the Yucca Formation. The goals of this project are to 1. construct a carbon isotope chemostratigraphic record of the Yucca Formation, and 2. correlate the Yucca Formation with strata of similar age using chemostratigraphy. Methods: 163 samples were collected from Big Bend Ranch State Park (BBRSP) to determine the δ[sup 13]C value of bulk sedimentary organic matter. Results: C-isotope values range from -27.02‰ to -18.42‰. Discussion: Carbon isotope excursions (CIEs) that are associated with the Aptian-Albian Boundary are identified as well as CIEs associated with Oceanic Anoxic Events (1a and 1b). This allows us to conclude that the Aptian-Albian boundary is recorded within the Yucca Formation strata at about 71 m above the base of the section exposed in the Lower Shutup of the Solitario in Big Bend Ranch State Park. Regional correlation of the Yucca Formation to other chemostratigraphic records from other Cretaceous strata suggests that the Yucca Formation in BBRSP is time equivalent to the Sligo, Pine Island, James, Bexar, and a portion of the lower Glen Rose Formation on the Comanche Platform and to a portion of the lower Glen Rose Formation in Big Bend National Park. [ABSTRACT FROM AUTHOR]

The Kutch Basin of western India exposes one of the most complete, fossiliferous marine Cenozoic sedimentary sequences of India. Precise depositional ages of these sequences are of great importance in the reconstruction of palaeoclimatic and palaeobiogeographic histories of the basin. Due to the poorly constrained foraminiferal biostratigraphic ages, we conducted high‐resolution 87Sr/86Sr chronology of the various fossiliferous, stratigraphically continuous units of Oligocene–Miocene strata in Kutch Basin. Besides updating the previously determined 87Sr/86Sr chronology, we report new numerical depositional ages for Oligocene–Miocene formations and members, and correlated these ages to the existing biostratigraphic schemes. The new 87Sr/86Sr data indicates a depositional age range between 28.64 + 0.29/‐1.11 and 23.51 + 1.53/‐1.85 Ma (Rupelian‐Chattian) for the Maniyara Fort Formation, between 23.07 + 0.94/1.39 and 18.09 + 0.24/‐0.57 Ma (Chattian‐Burdigalian) for the Khari Nadi Formation, and between 15.11 + 0.56/‐2.87 and 12.29 + 1.22/‐1.9 Ma (Langhian‐Serravallian) for the Chhasra Formation. The sedimentation rate, determined through numerical ages derived from 87Sr/86Sr, indicates an increase in sedimentation for the Khari Nadi (0.23 ± 0.04 cm/kyr) and Chhasra (0.12 ± 0.04 cm/kyr) formations, likely related to uplift of the Himalaya‐Tibetan plateau and intensification of the Indian Summer Monsoon. The bulk sediment element ratios (V/Ni, Ni/Co and V/Cr) indicate oxic to suboxic palaeo‐redox conditions during deposition of the Oligocene–Miocene successions of the basin. Based on new and updated 87Sr/86Sr chronology, the depositional environments and sedimentation rates of the Kutch sequence are correlated with changes in sea‐level, sedimentation rates in the Arabian Sea and Bay of Bengal, and the global climate changes across the Oligocene–Miocene boundary. [ABSTRACT FROM AUTHOR]

The Sirban Limestone Formation (SLFm) dolostones cropping out in the Riasi Allochthon (NW Himalaya, Jammu, India) show a range of δ13C (−1.08 to 0.73‰) and δ18O (−11.50 to −7.82‰) values and the mean values of 0.15‰ and −9.12‰ Pee Dee Belemnite (PDB), respectively. The δ13C values indicate that these dolostones were deposited during Neoproterozoic, and the δ18O values also are very close to the average Mesoproterozoic carbonate values obtained from the coeval carbonates. The characteristic δ13C values have the potential to provide an age constraint for the SLFm, and the mean δ18O value is comparable to the 'best preserved' δ18O mean value (−7.5 ± 2‰) reported for most of the Meso-Neoproterozoic to Early Cambrian carbonates. δ13C vs. δ18O plot for the SLFm suggests normal marine origin with late-stage cementation. In the present study, stable isotope geochemistry of the SLFm dolostones is attempted. Preliminary data on the major-and-minor elemental composition of SLFm has also been presented. In addition, several petrographic facies identified in the SLFm have also been documented here. Diagenesis characterisation of these facies show dolomitization represents an important phase in the early diagenesis process. The subsequent diagenetic stages range from early seafloor cementation to late-stage tectonic stylolitisation, which have obliterated the original textures to dominant diagenetic textures, also reflected in the δ13C and δ18O values. Similar isotope profiles can be potentially significant for the chemostratigraphic correlation of different sections within the Riasi Allochthon and coeval equivalents regionally and globally. [ABSTRACT FROM AUTHOR]

We present a multi-proxy investigation of a lower Carnian basinal succession from Polzberg in the Northern Calcareous Alps (Lower Austria). A section comprising a unique Konservat-Lagerstätte was studied based on bio- and chemostratigraphy along with geophysical methods, yielding a detailed and robust stratigraphic calibration of the Polzberg succession. The Polzberg section revealed the paleoceanographic history and helped to identify a global climatic reversal, the Carnian Pluvial Episode. The age of the Upper Triassic Reingraben formation in the Northern Calcareous Alps is refined as the Austrotrachyceras austriacum Zone within the lower Carnian (Julian 2). Ammonoids and conodonts provide a detailed biostratigraphic subdivision that serves as a basis for analyses of the faunal distribution and the paleoenvironmental evolution of the Upper Triassic Reifling Basin. The succession includes lithological and facies changes similar to those of coeval units in the Tethys. The Carnian was characterized by a weak (~ 1‰) positive δ13C trend, punctuated by a negative shift during the lower Carnian corresponding to the initiation of the Carnian Pluvial Episode, a period representing the onset of early/late Carnian transitional global greenhouse conditions. Organic maturity parameters and the conodont alteration index (CAI) show that the thermal overprint of the Polzberg section is low. Biomarker proxies suggest that the organic matter of the uppermost Göstling formation is a mixture of marine and terrestrial material deposited in a dysoxic environment. Within the overlaying Reingraben formation, the amount of marine biomass decreased gradually upwards. Oxygen-depleted conditions, probably due to water-column stratification, continued during deposition of the Reingraben formation. Bacterial sulfate reduction played a major role in organic matter degradation. [ABSTRACT FROM AUTHOR]

Correlating shallow shelf carbonates and their deep basin equivalents is a perennial challenge in the geosciences, with wideranging implications. This hurdle is well illustrated in the Llandovery succession of the Michigan Basin, USA, a 40- to 265-m-thick carbonate interval represented by three lithostratigraphic units: the Cataract, the Burnt Bluff, and the Manistique groups. Although extensively studied at various localities within the basin and across the region, the chronostratigraphic relationships between these units remain unknown. The current study presents a cross-basin chronostratigraphic framework for the Llandovery succession utilizing globally documented carbon (Î'13Ccarb) isotope excursions (CIEs). From 10 drill cores and three quarry sites throughout the Michigan Basin, five CIEs were identified and chronostratigraphically constrained using conodont biostratigraphy and conodont 87Sr/86Sr data. The five excursions are interpreted to be the global CIEs: the (1) Hirnantian Isotope Carbon Excursion (HICE; Hirnantian Stage), (2) Early Aeronian, (3) Late Aeronian (Aeronian Stage), (4) Valgu (Telychian Stage), and (5) Ireviken (Sheinwoodian Stage). Most importantly, the HICE and the Ireviken CIEs bracket the Llandovery strata preserved in the basin. The new high-resolution Î'13Ccarb data suggest that CIEs can be effectively used to correlate among shallow marine shelf carbonates and their deeper water equivalents. The new chronostratigraphic framework shows that CIE-based time horizons across the Michigan Basin cut across lithostratigraphic unit boundaries, which indicates that these lithostratigraphic units are diachronous in the Michigan Basin. In addition to refining the stratigraphy of the Llandovery succession of the Michigan Basin, particularly the timing of various key sedimentary deposits, the new chronostratigraphic framework can be used to: (1) constrain the timing of various regional tectonic phenomena, (2) identify multiple tectonically driven siliciclastic sediment pulses in the basin, and (3) predict various stratal relationships that may result in previously unknown stratigraphic traps and, therefore, new hydrocarbon plays within the basin. The results of the current study also show that Î'13Ccarb trends across the shelf-tobasin transect are spatially and temporally variable and do not match those reported in Modern carbonate settings, which possibly suggests that such Î'13Ccarb trends, to some extent, reflect variations in water circulation and water mass heterogeneity during deposition. [ABSTRACT FROM AUTHOR]

The Eocene Kuldana Formation (KF) in the Yadgar area of Pakistan, comprises a diverse range of sedimentary facies, including variegated red beds of shales, mudstones, and sandstones, as well as interbedded limestone and marl. In this study, we conducted an integrated micropaleontological, sedimentological, mineralogical, and geochemical investigation to determine the depositional setting, biochronology, provenance, and paleoclimate of the KF. The study identified six lithofacies and six microfacies, which indicate a variety of environments ranging from floodplains and channels to the margins and shallow marine settings. The nannofossil biostratigraphy places the KF in the Early Eocene, more precisely the NP10 zone (Ypresian), and the fossil zone of benthic foraminifera classifies the study section as the Shallow Benthic Zone SBZ-8 (Middle Ilerdian 2). In terms of petrography, the KF sandstone was classified as litharenite and feldspathic litharenite, while the QtFL diagram suggests a recycled orogen. Geochemical proxies indicate an oxidizing environment, a high-to-low regular sedimentation rate, moderate-to-intense chemical weathering in the source region, and a warm-humid to dry climate during the deposition of KF. Overall, the findings suggest that the deposition of KF marks the end of Neo-Tethys due to the Early Eocene Indian–Kohistan collision and that the uplifting of the Himalayas provided the source for the deposition of KF in the foreland basin. The study provides new insights into the depositional environment, biochronology, provenance, and paleoclimate of KF, and highlights the potential for red beds as reliable indicators of oxygenation levels in proximity to mineral deposits. [ABSTRACT FROM AUTHOR]

Several unconformities have been previously recognized in the Late Ordovician and early Silurian strata of southern Ontario. We examined the Georgian Bay, Queenston, Whirlpool, Manitoulin, Power Glen, and Cabot Head formations and associated unconformities. Detailed sequence stratigraphic and chemostratigraphic analysis of Late Ordovician and early Silurian outcrops between Niagara, New York, and Manitoulin Island, Ontario, reveals new insights on the timing of the erosional unconformities and the Ordovician–Silurian boundary. We recognize three significant lowstand unconformities in this interval, which are referred to as the Cherokee, S1B, and S2 unconformities. Additional small-scale surfaces are present but do not reflect any major change in sea level or pause in sedimentation. Using δ13Ccarb chemostratigraphy, biostratigraphy, and sequence stratigraphy, we tentatively correlate units and the mentioned unconformities from southern Ontario to other eastern North American sections of comparable age, showing how glacioeustasy had a widespread effect on the deposition and removal of strata in far-field, subtropical basins. The Cherokee unconformity appears to be a composite erosion surface found across eastern North America that formed during the two or more episodes of glacioeustatic sea level fall in the early to middle Hirnantian. The overlying S1B and S2 unconformities can also be found across eastern North America and appear to be the result of glacioeustatic sea level falls occurring during the early Silurian. These new insights on the timing of erosional unconformities help better constrain the placement of the Ordovician/Silurian boundary in Ontario. It appears that the boundary does not correspond to a lowstand-related disconformity as previously suggested but can be tentatively placed within the Power Glen or lower Cabot Head formations. [ABSTRACT FROM AUTHOR]

Abstract Earth scientists have leveraged carbon isotope records to interpret Earth history and establish chronostratigraphic frameworks for decades (e.g., Halverson et al., 2005, https://doi.org/10.1130/b25630.1; Kaufman & Knoll, 1995, https://doi.org/10.1016/0301‐9268(94)00070‐8; Knoll et al., 1986, https://doi.org/10.1038/321832a0; Saltzman & Thomas, 2012, https://doi.org/10.1016/b978‐0‐444‐59425‐9.00011‐1; Scholle & Arthur, 1980, https://doi.org/10.1306/2f91892d‐16ce‐11d7‐8645000102c1865d). Increasingly detailed and nuanced approaches have been applied to understanding carbon isotope records in light of local‐ and regional‐scale processes that complicate interpretations. The recent work of Gazdewich et al. (2024, https://doi.org/10.1029/2023gc011376) is a prescient example, in which they conduct a series of analyses to constrain the influence of authigenic carbonate burial on the global carbon isotope mass balance during the Late Devonian. Here, I briefly review some recent developments in quantitative approaches to understanding carbon isotope values measured from carbonate rocks (δ13Ccarb), with a focus on comparisons of measured δ13Ccarb values, models for understanding what controls δ13Ccarb values, and correlation tools for aligning δ13Ccarb stratigraphies. These new approaches are elucidating carbon isotope records across Earth history and may prove to be transformative for our understanding of the global carbon cycle.

Introduction: The Yucca Formation is a Lower Cretaceous sedimentary unit present in West Texas. Based on its relative stratigraphic position in the Cretaceous succession of West Texas, it is expected that the Yucca Formation is of Albian and/or Aptian age. It is also expected that the carbon isotope excursions associated with OAE 1a and OAE 1b should be identified in the Yucca Formation. The goals of this project are to 1. construct a carbon isotope chemostratigraphic record of the Yucca Formation, and 2. correlate the Yucca Formation with strata of similar age using chemostratigraphy.Methods: 163 samples were collected from Big Bend Ranch State Park (BBRSP) to determine the δ13C value of bulk sedimentary organic matter.Results: C-isotope values range from −27.02‰ to −18.42‰.Discussion: Carbon isotope excursions (CIEs) that are associated with the Aptian-Albian Boundary are identified as well as CIEs associated with Oceanic Anoxic Events (1a and 1b). This allows us to conclude that the Aptian-Albian boundary is recorded within the Yucca Formation strata at about 71 m above the base of the section exposed in the Lower Shutup of the Solitario in Big Bend Ranch State Park. Regional correlation of the Yucca Formation to other chemostratigraphic records from other Cretaceous strata suggests that the Yucca Formation in BBRSP is time equivalent to the Sligo, Pine Island, James, Bexar, and a portion of the lower Glen Rose Formation on the Comanche Platform and to a portion of the lower Glen Rose Formation in Big Bend National Park.

The Upper Silesian Coal Basin (USCB), located in southern Poland, is the major coal basin in Poland, and all technological types of hard coal, including coking coal, are exploited. It is also an area of high potential for coal-bed methane (CBM). Despite the increasing availability of alternative energy sources globally, it is a fact that the use of fossil fuels will remain necessary for the next few decades. Therefore, research on coal-bearing formations using modern research methods is still very important. The application of geochemistry and chemostratigraphy in reservoir characterization has become increasingly common in recent years. This paper presents the possibility of applying chemostratigraphic techniques to the study of the Carboniferous coal-bearing succession of the Upper Silesian Coal Basin. The material studied comes from 121 core samples (depth 481–1298 m), representing the Mudstone Series (Westphalian A, B). Major oxide concentrations of Al2O3, SiO2, Fe2O3, P2O5, K2O, MgO, CaO, Na2O, K2O, MnO, TiO2, and Cr2O3 were obtained using X-ray fluorescence (XRF) spectrometry. Trace elements were analyzed using inductively coupled plasma mass spectrometry (ICP/MS). The geochemical record from the Mudstone Series shows changes in the concentration of major elements and selected trace elements, leading to the identification of four chemostratigraphic units. These units differ primarily in the content of Fe, Ca, Mg, Mn, and P as well as the concentration of Zr, Hf, Nb, Ta, and Ti. The study also discusses quartz origin (based on SiO2 and TiO2), sediment provenance and source-area rock compositions (based on Al2O3/ TiO2, TiO2/Zr, and La/Th), and paleoredox conditions (based on V/Cr, Ni/Co, U/Th, (Cu+Mo)/Zn, and Sr/Ba) for the chemostratigraphic units. Chemostratigraphy was used for the first time in the study of the Carboniferous coal-bearing series of the USCB, concluding that it can be used as an effective stratigraphic tool and provide new information on the possibility of correlating barren sequences of the coal-bearing succession. [ABSTRACT FROM AUTHOR]

In the Late Permian Zechstein Sea of Central Europe, up to 2000 m of evaporitic rocks were deposited in at least four consecutive cycles. The age of these evaporitic rocks could not yet be precisely determined, because they are virtually fossil-free and do not contain radiometrically datable volcanic layers. A chemostratigraphic age of the succession can be determined by comparing 87Sr/86Sr ratios of marine gypsum and anhydrite to the worldwide marine strontium evolution curve. Unfortunately, published 87Sr/86Sr data of the Zechstein succession are characterized by frequent outliers towards higher ratios, making an age assignment challenging. The scatter in 87Sr/86Sr ratios might be induced by different processes like the contribution of meteoric water to the brine, in-situ Rb decay, or post-depositional hydrothermal or diagenetic overprint. Here, we present a dataset of 26 new gypsum and anhydrite 87Sr/86Sr ratios from drill cores situated at "Alter Stolberg" in the northernmost Thuringian Basin. Evaporites of the Werra-, Staßfurt-, and Leine cycles were sampled. The close proximity of the drillings allows a very accurate assignment of the stratigraphic position of each sample, so that trends and outliers in 87Sr/86Sr ratios can easily be recognized. While the entire Werra Formation obviously revealed non-marine 87Sr/86Sr ratios, the lowermost 87Sr/86Sr ratios in the Staßfurt and Leine Formations can be assumed to represent marine ratios and allow estimating a chemostratigraphic age of 257‒254 Ma. The combination of the 87Sr/86Sr data with the mineral composition of the samples suggests a contribution of meteoric water, probably river water, to the Zechstein Sea as the main reason for the observed increase in 87Sr/86Sr ratios. Additional in-situ Rb decay, related to the riverine input of clay minerals, cannot be excluded. Modelling the amounts of sea water and meteoric water in the brine indicates that 83‒99% of meteoric water would be necessary to explain the highest 87Sr/86Sr ratios observed in the Werra Formation. [ABSTRACT FROM AUTHOR]

Analysis of biostratigraphically dated boulders demonstrates that the Steptoean Positive Carbon Isotope Excursion (SPICE) is recorded in debris flow conglomerates of the Downes Point Member of the Shallow Bay Formation in western Newfoundland. Fifteen boulders composed of bioclastic carbonates were assigned to five faunas based on assemblages of agnostids and trilobites. The Glyptagnostus reticulatus and "Innitagnostus" inexpectans faunas correlate into strata that record the rising limb of the SPICE in its type area of Nevada and Utah, whereas equivalents of the Acmarhachis kindlei Fauna lie in the interval that records peak δ13C values. The Crepicephalus and Triorygma burkhalteri faunas correlate into pre- and post-SPICE strata, respectively. δ13C values for boulders from the three faunas correlative with the SPICE are significantly higher than "background" levels of the pre- and post-SPICE boulders, but the maximum value in the A. kindlei Fauna (1.5‰) is less than half of the peak values recorded in Nevada and Utah. The values are, however, in line with those reported from the Port au Port Peninsula of Newfoundland, which reach 2.2‰. The differences in magnitude between Newfoundland and Nevada–Utah hint at differences in the expression of the SPICE in different geographic regions of the Laurentian continent that might reflect oceanographic conditions. [ABSTRACT FROM AUTHOR]

During the latest Mesoproterozoic–Early Neoproterozoic era, extensional regimes generated a number of sedimentary basins in various regions in the Sino-Korean Craton. Mantle-plume emplacements are widely recognized in the sedimentary strata as mafic dikes and sills of the Dashigou Large Igneous Province (LIP). The occurrence of Fe-rich redbeds is first reported in the Neoproterozoic Socheong Formation of the Sangwon Supergroup in the Pyeongnam Basin. Their geochemical and mineralogical characteristics indicate basin-wide Fe enrichment due to hydrothermal fluid input. The episodic yet repetitive hydrothermal injection into the basin generated short-lived anoxia, recorded as greenish-gray coloration in the ferruginous beds. This hydrothermal fluid was likely sourced from the mafic igneous activities involved in the Dashigou LIP. The redbeds can be utilized as key beds for intra- or inter-basinal stratigraphic correlation and to study the negative carbon isotope excursions that occurred in the genetically related basins in the region (e.g., the Sangwon, Xu-Huai, and Dalian basins). [ABSTRACT FROM AUTHOR]

Lithology of the Lower Frasnian (Upper Devonian) sections, including the Zhelon Regional Stage and the Saria Beds of the Sargaevo Regional Stage, exposed in the basin of the Saryanka River, the Latvian Saddle, is described. The complete lithological description of the Sargaevo and Semiluki deposits (Frasnian) in the Gralevo quarry of the Vitebsk Region, Orsha Depression is presented. Photographic images of macro- and micro-dimensional remains of heterostracans, placoderms, acanthodians, sarcopterygians, actinopterygians, as well as scolecodonts and conodonts found in the Lower Frasnian deposits are presented. For the first time, the Sr isotope composition was measured in remains of ichthyofauna from the Zhelon and Sargaevo deposits of Belarus. Paleoichthyological and taphonomic data, lithology and Sr isotope composition of ichthyofauna fragments, depositional environments in the Zhelon and Saria times were clarified, and the distant sections were correlated. The 87Sr/86Sr values in ichthyofauna samples from the Saria Beds in sections of the Latvian Saddle (sections of Kalyuty 5a and 6, Virenka 1) and the Orsha Depression (Gralevo quarry) lie within similar ranges: 0.70825–0.70842 and 0.70837–0.70856, respectively. The 87Sr/86Sr values in ichthyofauna from the Zhelon deposits in the Kalyuty 2 and Obukhovo 1 sections (Latvian Saddle) vary within 0.70898–0.70932 and 0.71065–0.71102, respectively. High 87Sr/86Sr values in the fossil ichthyofauna of both regional stages suggest that the Early Frasnian paleobasin was significantly desalinated, while the salinity in the Saria paleobasin was comparable to the salinity of the modern Baltic Sea. [ABSTRACT FROM AUTHOR]

Cambrian System at the Shatan Section in northern Henan, North China, consists of sedimentary successions of tidal flat and shallow-water carbonate platform facies. Data of carbon isotope (δ13Ccarb) from this section reveals five positive δ13Ccarb (Pst-l–Pst-5) and five negative δ13Ccarb excursions (Nst-l–Nst-5). In the positive excursions, δ13Ccarb rises to 0.88‰, 1.05‰, 2.04‰, 1.00‰ and 2.97‰, respectively, while in the negative excursions δ13Ccarb drops to −8.00‰, −3.50‰, −1.00‰, −0.33‰ and around −2.00‰, respectively. On the basis of chronostratigraphy of Cambrian, the most remarkable carbon isotope excursions can be correlated regionally and globally. In addition, one second-order and ten third-order sequences have been recognized at this section. Correlating third-order sequences and chemostratigraphy indicates that carbonates from the basal part of the transgression system tract (TST) and the upper part of the high-water system (LHST) generally have lighter δ13Ccarb values, whereas massive carbonates with microbialite from the lower part of the high-water system tract (EHST) usually have heavier δ13Ccarb values. The association of δ13Ccarb values with sea-level fluctuations suggests that the positive carbon isotope excursions or high δ13Ccarb values may have been caused by an increase in the marine primary productivity in response to maximum seawater flooding during the transgression. [ABSTRACT FROM AUTHOR]

Three stratigraphic sections were sampled to demystify the geochemical properties of the shallow marine Govanda Formation, located in the Arabia–Eurasia suture zone at ~ 1500 m above sea level. This study examined the geochemistry of major, trace, rare earth elements (REE) and the petrography of carbonate rocks of the lower–middle Miocene Govanda Formation. Microfacies analysis shows that packstone and wackestone dominate the ticker western section, whereas the eastern sections contain grainstone and clastic units. The carbonates were deposited in shallow marine reef-fore-reef environments unaffected by diagenetic alterations. The limestone beds have a consistent seawater-like REE pattern, slightly negative Ce anomalies (Ce/Ce* = 0.79 in massive limestone–MSL and = 0.89 in marly limestone–ML), relatively positive Eu anomalies (Eu/Eu* = 1.18 in MSL and = 1.14 in ML), and moderately high Y/Ho ratios (37.69 n = 29). The REE + Y pattern of samples mainly retains its original characters, but the variations in the total rare earth element (ΣREE) content are detected, which could reflect minor detrital material inputs. Authigenic U, negative Ce anomalies, and trace element ratio indices such as V/Cr, U/Th, Ni/Co, and V/(V + Ni) indicate suboxic–anoxic deposition condition. A positive correlation of Al2O3% contents with Fe2O3% links the carbonate units of the Govanda Formation to marine limestones. The Rb–Sr-Ba ternary diagram, and Sr/Ba vs. Sr/Rb, Al2O3% vs. Fe2O3%, and Ce/Ce* vs. Sm/Yb bivariate analyses imply that the studied limestones originated in a passive margin tectonic setting. [ABSTRACT FROM AUTHOR]

A detailed record of the δ13Сorg value has been obtained for the first time in Permian mudstones of the Taskan Basin (Omulevka Block, Northeast Asia) covering the interval from the Upper Kungurian, Roadian, Wordian, Capitanian, and Lower Wuchiapingian stages. The value of δ13Сorg varies from –23.81‰ (mid-Kungurian) to –26.97‰ (lower Wuchiapingian). Three δ13Сorg negative excursions were clearly distinguished in the section including the upper part of the Kungurian Stage of the Lower Permian, the lower part of the Capitanian, and the boundary between the Capitanian and Wuchiapingian stages. These excursions are in good agreement with the episodes of mass extinction that we established earlier [12], and they are most likely associated with periods of activity of island-arc magmatism in the region during the Permian. [ABSTRACT FROM AUTHOR]

The Sr-isotopic composition in carbonate rocks aged 980–920 Ma has been defined in only one place in the world, the Huainan Formation of the North China Platform, with the accumulation time limited by U–Pb data of detrital zircon grains. The upper part of the Nizhny Tunguska Formation in the Turukhansk uplift is found to contain altered volcanic rocks, as well as weathering crust products along them, such as poor bauxite and chamosite ores, among carbonate deposits. Based on U–Pb zircon isotope dating, the age of the volcanic rocks is 963 Ma. For the least altered limestones in the upper part of the Nizhny Tunguska Formation, the 87Sr/86Sr values were obtained equal to 0.70532–0.70578, which are close to those found in the rocks of the Huainan Formation. These data about the geochronological age of the studied limestones make it possible to obtain more accurate data, which allows refining the previously proposed configuration of the Sr-isotopic composition variation curve in the Early Neoproterozoic. The Nizhny Tunguska Formation compares favorably with the Huainan Formation in being the world's only Early Neoproterozoic carbonate sequence that is correctly geochronologically substantiated (based on zircon from subsynchronous volcanic rocks). [ABSTRACT FROM AUTHOR]

Sequence stratigraphy is a commonly used approach to understand basin-fill history and the occurrence of conventional reservoir and/or probable source rocks. Reconstructing a sequence stratigraphic framework in carbonates, marls, and organic-rich mudstones is challenging due to environmental, petrophysical, and sedimentological variations that can be subtle, whereas seismic data may be lacking or of limited use. For this reason, incorporation between palynological analysis and chemostratigraphic profiles is becoming increasingly common to facilitate sequence stratigraphic reconstruction. This study investigates the Quse (lower Toarcian) and Sewa formations (upper Bajocian-Bathonian) in the Bilong Co section from the Qiangtang Basin of central Tibet. Eighty-three rock samples were analysed for their whole-rock inorganic geochemical composition, of which 25 rock samples were tested for palynological and palynofacies analyses. The palynological composition defined two associations for the study section. The lower part of the Bilong Co section consisted is dominated by a moderate to high abundance of opaque phytoclasts versus low to moderate amorphous organic matter (AOM) content with a high concentration of sphaeromorphs pollen grains, revealing deposition of this interval at times of low relative sea level in fluvio-deltaic settings. The middle to upper parts of the section comprised of significantly high AOM content versus low phytoclasts and high content of sphaeromorphs pollen grains, but with increasing the relative abundance of dinoflagellate cysts, indicating a phase of high sea level. Chemostratigraphic variations relevant to changes in relative sea level delineated the subdivision of the Quse and Sewa formations into two and three third-order transgressive-regressive sequences, respectively. The collision between the Lhasa and Qiangtang blocks during the Early-Middle Jurassic is suggested to control consequent subduction and sea level highstand, especially during deposition of the Sewa Formation. Geochemical proxies that relate to shelf carbonate production are calcium, strontium, whereas proxies that relate to siliciclastics include titanium, zirconium, manganese, aluminium, and silicon, other redox-sensitive proxy like uranium is also implemented. This indicates that chemostratigraphic proxies are a promising tool for the interpretation of sea level cyclicity in terms of systems tracts and bounding surfaces. [ABSTRACT FROM AUTHOR]

Drilling for the International Continental Scientific Drilling Program (ICDP) Early Jurassic Earth System and Timescale project (JET) was undertaken between October 2020 and January 2021. The drill site is situated in a small-scale synformal basin of the latest Triassic to Early Jurassic age that formed above the major Permian–Triassic half-graben system of the Cheshire Basin. The borehole is located to recover an expanded and complete succession to complement the legacy core from the Llanbedr (Mochras Farm) borehole drilled through 1967–1969 on the edge of the Cardigan Bay Basin, North Wales. The overall aim of the project is to construct an astronomically calibrated integrated timescale for the Early Jurassic and to provide insights into the operation of the Early Jurassic Earth system. Core of Quaternary age cover and Early Jurassic mudstone was obtained from two shallow partially cored geotechnical holes (Prees 2A to 32.2 m below surface (m b.s.) and Prees 2B to 37.0 m b.s.) together with Early Jurassic and Late Triassic mudstone from the principal hole, Prees 2C, which was cored from 32.92 to 651.32 m (corrected core depth scale). Core recovery was 99.7 % for Prees 2C. The ages of the recovered stratigraphy range from the Late Triassic (probably Rhaetian) to the Early Jurassic, Early Pliensbachian (Ibex Ammonoid Chronozone). All ammonoid chronozones have been identified for the drilled Early Jurassic strata. The full lithological succession comprises the Branscombe Mudstone and Blue Anchor formations of the Mercia Mudstone Group, the Westbury and Lilstock formations of the Penarth Group, and the Redcar Mudstone Formation of the Lias Group. A distinct interval of siltstone is recognized within the Late Sinemurian of the Redcar Mudstone Formation, and the name "Prees Siltstone Member" is proposed. Depositional environments range from playa lake in the Late Triassic to distal offshore marine in the Early Jurassic. Initial datasets compiled from the core include radiography, natural gamma ray, density, magnetic susceptibility, and X-ray fluorescence (XRF). A full suite of downhole logs was also run. Intervals of organic carbon enrichment occur in the Rhaetian (Late Triassic) Westbury Formation and in the earliest Hettangian and earliest Pliensbachian strata of the Redcar Mudstone Formation, where up to 4 % total organic carbon (TOC) is recorded. Other parts of the succession are generally organic-lean, containing less than 1 % TOC. Carbon-isotope values from bulk organic matter have also been determined, initially at a resolution of ∼ 1 m, and these provide the basis for detailed correlation between the Prees 2 succession and adjacent boreholes and Global Stratotype Section and Point (GSSP) outcrops. Multiple complementary studies are currently underway and preliminary results promise an astronomically calibrated biostratigraphy, magnetostratigraphy, and chemostratigraphy for the combined Prees and Mochras successions as well as insights into the dynamics of background processes and major palaeo-environmental changes. [ABSTRACT FROM AUTHOR]

This paper presents geochemical data for 171 core samples of the Carboniferous coal-bearing series and the Miocene cove from the central part of the Upper Silesian Coal Basin. Major oxide concentrations (Al2O3, SiO2, Fe2O3, P2O5, K2O, MgO, CaO, Na2O, K2O, MnO, TiO2, and Cr2O3) were obtained using XRF. Trace and major elements (Mo, Cu, Pb, Zn, Ni, Co, U, Cr, V, Mn, As, Th, Sr, Cd, Sb, Bi, Ba, Ti, W, Zr, Ce, Nb, Ta, Be Sc) were analysed ICP-MS. The main goals of this study were to demonstrate the distribution, as well as the stratigraphical variability, of the selected elements and to determine whether chemostratigraphy tools could be effectively applied to analyze Carboniferous and Miocene deposits of the USCB. Geochemical studies have shown showed different geochemical features of the samples from the Carboniferous and the Miocene. The diversity is mainly expressed in the enrichment of Miocene sediments in Ca and Sr related to biogenic carbonate material. It was also stated that the concentrations of trace elements associated with the detrital fraction, such as Zn, Cr, Co, Ba, Ti, Zr, Nb, and Sc show slightly higher values in Carboniferous sediments. On the basis of the content of Ti, Zr, and Nb, as well as ratios such as Th/U, Zr/Th, Ti/Zr, and TiO2/K2O, units with different inputs of the terrigenous fraction can be identified in both Carboniferous and Miocene formations. The paper shows that chemostratigraphy can be used as a stratigraphic and correlation tool for the Carboniferous and the Miocene deposits of the USCB. [ABSTRACT FROM AUTHOR]

The age of sedimentation (530–520 Ma) of the Teregtig Formation of South Tuva is estimated on the basis of U–Pb dating of detrital zircon grains from terrigenous rocks and Sr chemostratigraphy of carbonate rocks. It is shown that granitoids with an age of 580 Ma were the main source of detrital zircon. The presence of a representative Precambrian detrital zircon population indicates the deposition of sediments of the Teregtig Formation within the continental crustal block with a long evolution. During the accumulation of coarse-grained rocks of the Teregtig Formation, this part of the eroded area also comprised rocks of the Agardag ophiolite massif, which is evident from numerous angular clasts of olivine, pyroxenes, and Cr-spinels in the conglomerate matrix. [ABSTRACT FROM AUTHOR]

The present study focuses on determining the position of the lower boundary of the Silurian System in the eastern Baltic region. To achieve this, we conducted a comprehensive analysis of stable isotopic curves, combined with previously published data on the graptolite record. Our isotopic correlations are primarily based on the δ13Corg curve of the Dobâs Linn section, the GSSP of the Silurian System, and the δ13Ccarb curve of the Monitor Range section in Nevada. Our results provide robust evidence for correlating the basal Varbola Formation, the lower part of the Ãhne Formation and the StaÄiÅ«nai Formation, and suggest their latest Ordovician age. The integration of stable isotopic data and graptolite records allows for a more accurate characterisation of the OrdovicianâSilurian boundary in this region.

Based on a new deep drilling on southern Gotland (Sweden), this study is the first to document the carbon isotope chemostratigraphy of the Upper Ordovician through lowermost Silurian sedimentary record from the central parts of the Baltic Sea subsurface. The lithological record of the Stora Sutarve core has similarities with adjacent successions in both the Viki core in the East Baltic area and the Borenshult core in the Swedish mainland. The core includes the Kahula (including 13 bentonites in the "Kinnekulle K-bentonite complex"), Hirmuse(?), Rägavere, Paekna, Jonstorp, Loka, Motala and Kallholn formations. Several of the internationally recognized upper Ordovician δ13C excursions have been identified in the core, including the Guttenberg Isotope Carbon Excursion (GICE), Moe excursion, Hirnantian Isotope Carbon Excursion (HICE), and an undefined early Silurian carbon isotope excursion, presumably the Early Aeronian Carbon Isotope Excursion (EACIE). We particularly address the microstratigraphy of the Hirnantian Stage and the finer details of the HICE, which is not fully complete and entirely confined to the 2.09-m-thick Loka Formation. This formation yields abundant, but low-richness brachiopod faunas characteristic of the Hirnantian Stage and is, based on erosional-depositional surfaces and facies, interpreted as reflecting interglacial warming and eustatic transgression related to ice-sheet contraction in Gondwana. Based on very dense carbon isotope sampling we identify four clusters of δ13C values that aid to define significant changes in the preserved record of the HICE and which may facilitate global correlation of the succession and the herein interpreted sea-level record. [ABSTRACT FROM AUTHOR]

The depression of the ancient Lumparn meteorite impact structure is partly infilled by Cambrian and Ordovician sediments, lying nowadays below the seawater. The Ordovician carbonate succession at this site, recognised through erratic boulders and by the drilling project in the late 1950s, is of particular interest due to its isolated and distant location from other areas with Ordovician sediments in the Baltoscandian Palaeobasin. In this study, we present new data on ostracod biostratigraphy and stable carbon isotope chemostratigraphy obtained from three old drillcores. Comparison of ostracod distribution with sections in Estonia generally supports the previous interpretations of a Darriwilian and Sandbian age for the lowermost Tranvik Limestone (which we propose renaming the "orthoceratite limestone" in the Åland Islands area). The uppermost Östersjö Limestone spans almost the entire Katian age. We also observe the global MDICE and GICE carbon isotopic excursions, as well as Katian Rakvere and Saunja excursions, within the Lumparn succession. The Ordovician succession in Lumparn Bay is facially resembling the Estonian Shelf facies of the Baltoscandian Palaeobasin. [ABSTRACT FROM AUTHOR]

The Devonian–Carboniferous (D–C) transition coincides with the Hangenberg Crisis, carbon isotope anomalies, and the enhanced preservation of organic matter associated with marine redox fluctuations. The proposed driving factors for the biotic extinction include variations in the eustatic sea level, paleoclimate fluctuation, climatic conditions, redox conditions, and the configuration of ocean basins. To investigate this phenomenon and obtain information on the paleo‐ocean environment of different depositional facies, we studied a shallow‐water carbonate section developed in the periplatform slope facies on the southern margin of South China, which includes a well‐preserved succession spanning the D–C boundary. The integrated chemostratigraphic trends reveal distinct excursions in the isotopic compositions of bulk nitrogen, carbonate carbon, organic carbon, and total sulfur. A distinct negative δ15N excursion (~−3.1‰) is recorded throughout the Middle Si. praesulcata Zone and the Upper Si. praesulcata Zone, when the Hangenberg mass extinction occurred. We attribute the nitrogen cycle anomaly to enhanced microbial nitrogen fixation, which was likely a consequence of intensified seawater anoxia associated with increased denitrification, as well as upwelling of anoxic ammonium‐bearing waters. Negative excursions in the δ13Ccarb and δ13Corg values were identified in the Middle Si. praesulcata Zone and likely resulted from intense deep ocean upwelling that amplified nutrient fluxes and delivered 13C‐depleted anoxic water masses. Decreased δ34S values during the Middle Si. praesulcata Zone suggests an increasing contribution of water‐column sulfate reduction under euxinic conditions. Contributions of organic matter produced by anaerobic metabolisms to the deposition of shallow carbonate in the Upper Si. praesulcata Zone is recorded by the nadir of δ13Corg values associated with maximal △13C. The integrated δ15N‐δ13C‐δ34S data suggest that significant ocean‐redox variation was recorded in South China during the D–C transition; and that this prominent fluctuation was likely associated with intense upwelling of deep anoxic waters. The temporal synchrony between the development of euxinia/anoxia and the Hangenberg Event indicates that the redox oscillation was a key factor triggering manifestations of the biodiversity crisis. [ABSTRACT FROM AUTHOR]

The Paleocene–Eocene Thermal Maximum (PETM) represents the most pronounced hyperthermal of the Cenozoic era and is hypothesized to have resulted in an intensification of the paleohydrologic cycle, including enhanced seasonality and increased sediment discharge to the coastal ocean. Although the PETM has been widely documented, there are few records from deposits that form the distal, deepwater components of large sediment-routing systems. This study presents new constraints on the stratigraphic placement of the PETM in the deepwater Gulf of Mexico basin through analysis of geochemical, carbon isotopic, and biostratigraphic data within a ∼124 m cored interval of the Wilcox Group. Biostratigraphic and carbon isotopic data indicate that the PETM extends over ∼13 m based on acmes in the dinoflagellate Apectodinium homomorphum and calcareous nannoplankton Rhomboaster cuspis as well as a ∼-2 ‰ shift in bulk organic δ13 C values. A decrease in bioturbation and benthic foraminifera suggests that a reduction in oxygen of Gulf of Mexico bottom waters and/or an increase in sedimentation rates were coincident with the onset of the PETM. A ∼2 m lag in the depositional record separates the onset of the PETM negative carbon isotope excursion (CIE) and deposition of a 5.7 m thick interval of organic-lean claystone and marlstone that reflects a shut-off of the supply of sand, silt, and terrestrial palynomorphs to the basin. We interpret deposits of the PETM in the deepwater Gulf of Mexico to reflect the combined effects of increased erosional denudation and rising sea level that resulted in sequestration of sand and silt near the coastline but that allowed delivery of terrigenous mud to the deep sea. The similarity of oceanographic changes observed in the Gulf of Mexico and Atlantic Ocean during the PETM supports the inference that these water masses were connected during latest Paleocene–earliest Eocene times. Although deposition of typical Wilcox Group facies resumed during and after the PETM recovery, an increased influx of terrestrial detritus (i.e., pollen, spores, terrestrial organic debris) relative to marine dinoflagellates is suggestive of long-lasting effects of the PETM. This study illustrates the profound and prolonged effects of climatic warming on even the most distal reaches of large (≥1×106 km 2) sediment-routing systems. [ABSTRACT FROM AUTHOR]

The Early Cretaceous is an important time of transition in Earth history, marked by a succession of oceanic anoxic events and carbon cycle perturbations that drove changes on land and in the ocean. The need for more precise geochronologic constraints in terrestrial sediments of Early Cretaceous age that record faunal and floral transitions is especially critical. The Cedar Mountain Formation (CMF) is a continental lithostratigraphic unit that hosts a trove of paleoclimate archives and important dinosaurian fossil localities. Determining the timing of deposition of CMF strata has been an ongoing effort for many years. Here, we present new lithostratigraphic and carbon isotope chemostratigraphic data along with high‐precision radiometric ages to further constrain the Ruby Ranch Member of the CMF at a unique locality referred to as "Lake Carpenter," where a thick section of dominantly lacustrine strata overlies fluvial‐overbank to palustrine strata more typical of other Ruby Ranch Member outcrops. A bentonite bed near the base of the section provides one of the most precise ages yet determined within the Ruby Ranch Member of 115.92 ± 0.14 Ma via CA‐ID‐TIMS U‐Pb analysis of zircons. The age and the trends in the carbon isotope record indicate that the Lake Carpenter sediments were deposited entirely within the late Aptian Stage. These unique new data provide an important step toward improving our understanding of the timing of Early Cretaceous evolutionary and paleoclimate events. Plain Language Summary: This paper presents a new continental record from the Aptian Stage of the Cretaceous, roughly 116 million years ago. The record comes from a series of sedimentary rocks near Moab, Utah. The sedimentary rocks provide evidence of carbon cycle perturbations and environmental change as recorded by long‐lived lake sediment deposition as well as a new precise age to constrain the timing of the deposit. Key Points: New high precision radiometric age within the Ruby Ranch Member of the Cedar Mountain Formation of 115.92 ± 0.14 MaData constrain the age of important transitions in dinosaur and other terrestrial fauna and flora in North AmericaTerrestrial evidence of Aptian Carbon Cycle Perturbations namely the Jacob Event [ABSTRACT FROM AUTHOR]

The timing and character of the initial marine flooding of extensional basins has implications for their tectonic history. Yet, the recognition of such flooding is difficult along rift basin margins due to the dominance of coarse‐grained systems and the lack of marine fauna. This study conducts detailed facies and stratigraphic analysis of a Mio‐Pliocene alluvial fan and fan‐delta succession in the Fish Creek Vallecito Basin in southern California. Our goal is to characterize the marine flooding surface, determine the paleogeographic position of the shoreline and estimate the magnitude of relative base‐level rise that occurred during the marine incursion associated with the opening of the Gulf of California. Our results show that the flooding of the Elephant Trees alluvial fans is often marked by an abrupt lithologic and facies change from meter‐scale boulder‐rich subaerial debrites (proximal alluvial fan facies association) to centimetre‐scale granule‐rich subaqueous debrites, ripple‐laminated sandstones and mudstones (prodelta facies association). By delineating the zone of transition between the subaerial and subaqueous facies, we place the initial flooding paleo‐shoreline 4 km up the alluvial fan's paleo‐depositional slope. Considering alluvial fan slope gradients between 1° and 5°, this 4 km transgression would require an estimated 70–350 m of water depth during the initial marine incursion. Interfingering of fan‐delta deposits with subaqueous marine and planktonic‐rich evaporites suggests that the basin was below sea‐level after, and perhaps even before, the marine flooding. Subaerial subsea‐level basins exist in Death Valley and the Salton Trough today within similar extensional and transtentional tectonic regimes. This subaerial subsea‐level interpretation might explain the high magnitude and abrupt relative base‐level rise recorded by the facies transitions in the Fish Creek Vallecito Basin. These results suggest that the Fish Creek Vallecito Basin underwent significant extension during its early and nonmarine depositional phase, allowing it to reach subsea‐level elevations. The tectonic history of the Fish Creek Vallecito Basin maybe similar to other extensional basins where rapid subsidence allows the accumulation of nonmarine strata below sea‐level prior to the marine flooding, then restricted and deep marine strata immediately after flooding. [ABSTRACT FROM AUTHOR]

This study builds off the paleoclimatic reconstruction created by Hart et al. that used a multiproxy study to examine the role of moisture in the exodus of the Fremont from Range Creek Canyon in the 12th century. For this research, elemental ratios, weathering indices, and pollen data from two wetland spring sediment cores were used to compare with the existing Hart et al. paleoclimatic reconstruction (Objective 1). Elemental ratios and pollen data proved to be effective proxies for precipitation fluctuation, with the ratio of Pinus to Juniperus pollen representing effective moisture and increasing with the intensity of chemical weathering. Elemental data were additionally used to identify crypto tephra in the cores to validate Range Creek Canyon's existing chronology (Objective 2). The XRF analysis of the sediment cores constrained the chronology of environmental change in the canyon by identifying the elemental signature of the Mazama eruption (7627 ± 150 cal. year BP). The concentration of Al, Y, and Ti were 50 times higher in this layer than elsewhere in the core, indicating a sudden depositional event, such as a volcanic eruption. Based on the multiproxy data and confirmed chronology, the Fremont entered the canyon during a period of elevated precipitation lasting until 600 AD. Precipitation levels remained steady until 1200 AD, after which precipitation levels decreased, causing drought conditions that coincide with the Fremont's departure from Range Creek Canyon. [ABSTRACT FROM AUTHOR]

The following chemostratigraphy study was completed on the Permo–Carboniferous Unayzah Group in Eastern Saudi Arabia. The aim of the study was to determine whether the technique could be used to identify formation and member boundaries on a subregional scale, with the area extending for c. 550 km in a NW–SE direction and 350 km NE–SW. A total of 30 375 core and cuttings samples were analysed from 225 wells using ICP (Inductively Coupled Plasma) and XRF (X-ray Fluorescence) instruments, with data acquired for 42–53 elements for each sample in the range Na-U in the periodic table. Of these, details of 14 wells are discussed in the present work. Based on variations in Zr/Ti, Zr/U, Zr/Y, Y/U, U/Th, Gd/Zr, Nb/Yb and Nb/Th it is possible to identify a hierarchical order of one zone, four subzones and five divisions, these chemozones being correlative on a subregional scale. By comparing geochemical, biostratigraphic, sedimentological and wireline log data in selected reference wells, it was possible to relate chemozones to particular members of the Unayzah Group. The differences in geochemistry between these chemozones/members is largely explained by changes in provenance, though depositional environment may have exerted at least some influence. [ABSTRACT FROM AUTHOR]

The Middle Devonian (lower–middle Givetian) Hamilton Group of New York State is an iconic unit in North America, which has contributed many key concepts in stratigraphy, sedimentary geology, paleoecology, and evolution. This interval comprises a 100- to 1200-m-thick clastic wedge, shed westward from the Acadian Mountains, with thin but persistent carbonates. Despite the rich and diverse invertebrate fauna that consists of more than 300 species of corals, bryozoans, brachiopods, mollusks, echinoderms, and trilobites, the age of the Hamilton Group is rather poorly constrained in terms of chronostratigraphy owing to the rarity of biostratigraphically useful conodonts and goniatites. The upper part of the Hamilton Group that is the focus of this paper apparently belongs to the Polygnathus timorensis to middle Polygnathus ansatus Conodont chronozones. The middle to upper Hamilton Group in New York State comprises three formations—the Skaneateles, Ludlowville, and Moscow—each defined as an interval delimited with a sharply based fossiliferous limestone-calcareous siltstone; these formations are interpreted as containing condensed transgressive deposits overlain by thicker highstand to falling-stage shales, mudstones/siltstones, and sandstones. The eastern equivalents of these formations are dominated by fine-grained sandstones and siltstones and include two formations: the Panther Mountain Formation, equivalent to the Skaneateles and Ludlowville formations combined, and the Cooperstown Formation, equivalent to the Moscow Formation. In the present paper, we review, revise and update a hierarchical framework of lithostratigraphic subdivisions of these formations, including 24 members (four new), 50 submembers (more than half newly proposed or redefined; 14 informal at this time), and more than 80 named beds, both formal and informal. This refined lithostratigraphy provides an excellent framework for studying high-resolution sequence stratigraphy. As defined herein, members and most submembers represent high-frequency depositional sequences with basal shell-rich carbonates and abrupt flooding surfaces that mark the bases of highstand deposits. Not only are most of the members and submembers traceable across western and central New York, but also to a lesser extent into adjacent regions that include southern Ontario, Ohio, the Michigan Basin, and northeastern Pennsylvania. Nevertheless, much work on correlation remains to be done in eastern New York and central Pennsylvania, where local progradation of siliciclastics and expansion of successions obscures many of the finer scale features. [ABSTRACT FROM AUTHOR]