The aeolian deposits served as crucial archives for reconstructing terrestrial climatic conditions, atmospheric circulation patterns, and paleogeography. The Upper Cretaceous Chishan Formation in the Subei Basin is considered the easternmost aeolian deposit in Asia. However, substantial uncertainties remain regarding its sedimentary subfacies, the basin’s paleo-position relative to the Eastern Asian coastal mountain range, paleo-wind directions, provenance, and precise depositional age. This study conducted detailed stratigraphic logging, analysis of sedimentary structures, paleo-wind direction measurements, large-n detrital zircon U-Pb dating and sandstone modal analysis. The results reveal that the Chishan Formation comprises four sedimentary facies including aeolian dune, wet interdune, sandsheet, and ephemeral stream wadi facies, representing a wet aeolian system. Paleo-wind directions indicate dominant westerly patterns. The sandstones contain abundant volcanic lithic fragments. Large‑n detrital zircon dating yields a maximum depositional age of 86.64 ± 0.97 Ma. Quantitative top-down modeling reveals the provenance as being derived from the recycling of underlying Mesozoic strata (98 %), supported by detrital zircon data. Our data show that the Chishan Formation sandstones were formed through wind reworking and transportation of underlying aqueous sandstones, rather than via direct hurricane-driven transport. The Subei Basin is reinterpreted as having been situated on the leeward slope of the Eastern Asian coastal mountain ranges, and recently reported inferred glacial deposits within the Chishan Formation are refuted.
Unresolved spatial and temporal heterogeneities in deep-time marine shales restrict our understanding of ancient depositional dynamics. To address this scientific gap in the early Cambrian greenhouse world, this study integrates core data, power decomposition analysis (PDA), and sedimentary noise modeling from the Qiongzhusi Formation in the Deyang–Anyue Rift Trough, Sichuan Basin, China. Utilizing 2000 Monte Carlo simulations for correlation coefficient (COCO) and evolutionary COCO (eCOCO) testing, a continuous 10.72-Myr astronomical timescale is established, anchoring the basal shale at 526.2 Ma. A prominent ∼1.5-Myr obliquity modulation signal regulated chemical weathering intensity (validated by the Chemical Index of Alteration, CIA) to drive primary mineralogical differentiation. Intensified chemical weathering during obliquity maxima led to clay enrichment and feldspar depletion, whereas obliquity minima favored mechanical weathering and feldspar preservation. Furthermore, organic matter enrichment was co-modulated by astronomical pacing and local factors. In the basal E0 sublayer, enrichment was predominantly driven by hydrothermal nutrient supply, whereas in subsequent intervals, organic carbon accumulation followed a non-linear, hump-shaped threshold relationship with terrigenous clastic flux. These results reveal the fundamental control of orbital forcing on deep-time shale heterogeneity, improving paleoceanographic and paleoclimatic reconstructions of early Earth environments.
Carbonate minerals are ubiquitous in coal and can serve as long-term records of peat depositional environments, compositions of sediment-source rocks, paleo-climates, and alteration during coalification and subsequent epigenetic processes, as well as water–rock interactions associated with fluid movements. Given that the origins of carbonate minerals in coal remain poorly understood, this paper examined the isotopes of C-O-Sr in carbonate minerals from the No. 4 coal of the Dong Open-pit Mine, Ningwu coal field, Shanxi Province, China. The results show that carbonate (calcite and/or ankerite) mineralization within the coal is dominantly epigenetic. The C–O–Sr isotope data are consistent with a mixed-source model, in which carbonate precipitation involved isotopically light carbon derived from organic matter decarboxylation, meteoric groundwater–rock interaction, and a possible contribution from underlying Ordovician limestones. In contrast, carbonate mineralization in the overlying roof, underlying floor and interbedded parting layers reflects a combination of syngenetic and epigenetic processes. The low δ18O values indicate precipitation from 18O-depleted meteoric waters, whereas the 87Sr/86Sr signatures indicate interaction with carbonate-bearing strata, potentially including the underlying Ordovician limestones. However, the current dataset does not uniquely resolve the relative proportions of these possible sources, and additional contributions from dolomite, groundwater-mediated leaching, and adjacent strata cannot be excluded. These observations constrain the fluid sources of carbonate minerals in the coal-bearing succession, while indicating that the involvement of the underlying Ordovician limestones should be regarded as plausible rather than definitive.
Extraterrestrial impact events have played an important role in global environmental changes and mass extinctions throughout the Earth’s history. Detecting traces of these events in oceanic settings is often difficult because of post-impact sedimentation. The marine Os isotopic composition serves as a valuable stratigraphic indicator and provides a powerful tool for detecting extraterrestrial material in marine sediments because of its high sensitivity to global environmental changes. Here, we report a new discovery of a clay layer with a high concentration of Os (613 ppt) and a conspicuous negative Os isotope anomaly (0.32), indicative of increased influx of extraterrestrial material, from a sediment piston core obtained southwest of Minamitorishima Island, western North Pacific Ocean. To estimate the depositional age of the ejecta layer, we applied the Limited-memory Broyden–Fletcher–Goldfarb–Shanno with Box constraints fitting algorithm using 187Os/188Os profiles. Our results yielded a depositional age of ca. 12 Ma, consistent with the previously discovered ejecta layer in another sediment piston core obtained south of Minamitorishima Island. Our results provide additional petrographic and geochemical evidence of an extraterrestrial impact during the Middle Miocene.
