Search Results (316)

During the Pleistocene, the successive ice ages prompted the southward expansion of the “Mammoth Steppe” ecosystem, a prevalent habitat that supported species adapted to cold environments such as the mammoth, woolly rhinoceros, and reindeer. Previously, the earliest evidence for such cold-adapted species in the Iberian Peninsula dated back to Marine Isotope Stage 6 (MIS 6, ~191–123 ka). This paper reports the discovery of a reindeer (Rangifer) tooth from Unit GIII of the Galería site at the Atapuerca-Trinchera site complex, dated to MIS 8 (~300–243 ka). This find is significant as it represents not only the oldest evidence of glacial fauna in the Iberian Peninsula but also the southernmost occurrence of reindeer in Europe of this age. The presence of Rangifer at this latitude (42°21′ N) during MIS 8 suggests that the glacial conditions affected the Iberian fauna earlier and with greater intensity than previously understood. Over the subsequent climatic cycles, cold-adapted species spread further south, reaching Madrid (40°20′) during the penultimate glacial period and the province of Granada (37°01′) during the last glacial maximum. The coexistence of human fossils and lithic artefacts within Units GII and GIII at Galería indicates that early humans also inhabited these glacial environments at Atapuerca. This study elaborates on the morphological and archaeological significance of the reindeer fossil, emphasizing its role in understanding the biogeographical patterns of glacial fauna and the adaptability of Middle Pleistocene human populations. Full article

The Arctic Ocean is turning blue. Abrupt Arctic warming and amplification is driving rapid sea ice decline and irreversible deglaciation of Greenland. The already emerging, substantial consequences for the planet and society are intensifying and yet, model-based projections lack validatory consensus. To date, we cannot anticipate how a blue Arctic will respond to and amplify an increasingly warmer future climate, nor how it will impact the wider planet and society. Climate projections are inconclusive as we critically lack key Arctic geological archives that preserved the answers. This “Arctic Challenge” of global significance can only be addressed by investigating the processes, consequences, and impacts of past “greenhouse” (warmer-than-present) climate states. To address this challenge, the ERC Synergy Grant project Into the Blue (i2B) is undertaking a program of research focused on retrieving new Arctic geological archives of past warmth and key breakthroughs in climate model performance to deliver a ground-breaking, synergistic framework to answer the central question: “Why and what were the global ramifications of a “blue” (ice-free) Arctic during past warmer-than-present climates?” Here, we present the proposed research plan that will be conducted as part of this program. Into the Blue will quantify cryosphere (sea ice and land ice) change in a warmer world that will form the scientific basis for understanding the dynamics of Arctic cryosphere and ocean changes to enable the quantitative assessment of the impact of Arctic change on ocean biosphere, climate extremes, and society that will underpin future cryosphere-inclusive IPCC assessments. Full article

Red sandstones of the Cambrian age are globally distributed and represent an important sedimentation phase during this critical time interval. Their sedimentology and geochemistry can provide key information about the sedimentation style, paleoclimatic conditions, and weathering trends during the Cambrian. In the Salt Range of Pakistan, the Khewra Sandstone constitutes the Lower Cambrian strata and consists of red–maroon sandstones with minor siltstone and shale in the basal part. Cross-bedding, graded bedding, ripple marks, parallel laminations, load casts, ball and pillows, desiccation cracks, and bioturbation are the common sedimentary features of the formation. The sandstones are fine to medium to coarse-grained with subangular to subrounded morphology and display an overall coarsening upward trend. Petrographic analysis indicates that the sandstones are sub-arkose and sub-lithic arenites, and dolomite and calcite are common cementing materials. X-ray Diffraction (XRD) analysis indicates that the main minerals in the formation are quartz, feldspars, kaolinite, illite, mica, hematite, dolomite, and calcite. Geochemical analysis indicates that SiO₂ is the major component at a range of 53.3 to 88% (averaging 70.4%), Al₂O₃ ranges from 3.1 to 19.2% (averaging 9.2%), CaO ranges from 0.4 to 25.3% (averaging 7.4%), K₂O ranges from 1.2 to 7.4% (averaging 4.8%), MgO ranges from 0.2 to 7.4% (averaging 3.5%), and Na₂O ranges from 0.1 to 0.9% (averaging 0.4%), respectively. The results of the combined proxies indicate that the sedimentation occurred in fluvial–deltaic settings under overall arid to semi-arid paleoclimatic conditions with poor to moderate chemical weathering. The Khewra Sandstone represents the red Cambrian sandstones on the NW Indian Plate margin of Gondwana and can be correlated with contemporaneous red sandstones in the USA, Europe, Africa, Iran, and Turkey (Türkiye). Full article

Calls for an “archaeology of climate change” highlight the interest in integrating human land use histories with the paleoenvironmental record. Shifts in land use patterns, observed via regional archaeological surveys, have been used in studies exploring the relationships between human and environmental systems, often via the Adaptive Cycle (AC). Recent work has combined datasets from separate surveys to examine macroregional patterns, which can then be integrated with environmental proxy data. However, efforts at aggregating archaeological data are often problematized due to projects’ differing collection methods and periodizations. This study ascribes the formal constructs of the AC to survey data to minimize data aggregation issues and maintain local integrity. Aoristic sum functions were performed individually on data from four projects in the northeastern Peloponnese to identify local patterns. These data were then aggregated, allowing for changes in land use to be observed at the macro and regional levels. Further measurements relating to land use abandonment, continuity, expansion, and potential serve as proxy data to identify the AC constructs of organization, exploitation, conservation, and release. The approach allows for cross-comparative regional analysis and the creation of an aggregated dataset that describes macroregional trends, essential to integrating human and paleoenvironmental narratives over time. Full article

The Chacopampean Plain is a major physiographic unit in Argentina, bounded by the Colorado River to the south, the Sierras Pampeanas and Subandinas to the west, and the Paraná River, Río de la Plata Estuary, and the Argentine Sea to the east. Its subsurface preserves sediments from the Miocene marine transgression, while the surface hosts some of the country’s most productive soils. Two main geomorphological domains are recognized: fluvial systems dominated by alluvial megafans in the north, and aeolian systems characterized by loess accumulation and wind erosion in the south. The southern sector exhibits diverse landforms such as deflation basins, ridges, dune corridors, lunettes, and mantiform loess deposits. Despite their regional extent, the origin and chronology of many aeolian features remain poorly constrained, as previous studies have primarily focused on depositional units rather than wind-sculpted erosional features. This study integrates remote sensing data, field observations, and a synthesis of published chronometric and sedimentological information to characterize these aeolian landforms and elucidate their genesis. Our findings confirm wind as the dominant morphogenetic agent during Late Quaternary glacial stadials. These aeolian morphologies significantly influence the region’s hydrology, as many permanent and ephemeral water bodies occupy deflation basins or intermediate low-lying sectors prone to flooding under modern climatic conditions, which are considerably wetter than during their original formation. Full article

The Kaiparowits Formation preserves one of the best fossil records of Cretaceous North America, which provides great insight into the paleoecology. In an effort to investigate the paleohydrology of the Kaiparowits Formation, stable isotope compositions (δ¹³C, δ¹⁸O-carbonate, δ¹⁸O-phosphate) of 41 hadrosaur teeth, 27 crocodile teeth, and 35 turtle shell fragments were analyzed. The mean O-isotope compositions of drinking water (δ¹⁸O_w) calculated from the O-isotope of bioapatite (phosphate-δ¹⁸O_p) are −13.76 ± 2.08‰ (SMOW) for hadrosaur, −8.88 ± 2.76‰ (SMOW) for crocodile, and −10.14 ± 2.62‰ (SMOW) for turtle, which strongly reflect niche partitioning. The Kaiparowits formation does not fit the global trend in isotopic compositions of vertebrate skeletal remains from previous studies, which suggests a unique hydrological setting of the Kaiparowits basin. High-elevation runoff from the Mogollon Highlands and sea level fluctuation may have contributed to such a unique paleohydrology. Full article

The Aptian–Albian interval represents a significant cooling phase within the Cretaceous “hothouse” climate, marked by dynamic climatic fluctuations. High-resolution continental records are essential for reconstructing terrestrial climate and ecosystem evolution during this period. This study examines a lacustrine-dominated succession of the Shahezi Formation (Lishu Rift Depression, Songliao Basin, NE Asia) to access paleo-weathering intensity and paleoclimate variability between the Middle Aptian and Early Albian (c. 118.2–112.3 Ma). Multiple geochemical proxies, including the Chemical Index of Alteration (CIA), were applied within a sequence stratigraphic framework covering four stages of lake evolution. Our results indicate that a hot and humid subtropical climate predominated in the Lishu paleo-lake, punctuated by transient cooling and drying events. Periods of lake expansion corresponded to episodes of intense chemical weathering, while two distinct intervals of aridity and cooling coincided with phases of a reduced lake level and fan delta progradation. To address the impact of potassium enrichment on CIA values, we introduced a rectangular coordinate system on A(Al₂O₃)-CN(CaO* + Na₂O)-K(K₂O) ternary diagrams, enabling more accurate weathering trends and CIA corrections (CIA_corr). Uncertainties in CIA correction were evaluated by integrating geochemical and petrographic evidence from deposits affected by hydrothermal fluids and external potassium addition. Importantly, our results show that metasomatic potassium addition cannot be reliably inferred solely from deviations in A-CN-K diagrams or the presence of authigenic illite and altered plagioclase. Calculations of “excess K₂O” and CIA_corr values should only be made when supported by robust geochemical and petrographic evidence for external potassium enrichment. This work advances lacustrine paleoclimate reconstruction methodology and highlights the need for careful interpretation of weathering proxies in complex sedimentary systems. Full article

Continuing improvements in our understanding of ancient climate change renders it necessary to expand our toolkit for exploring human responses to climatic shifts. Currently, archaeological methods for exploring the resilience of ancient human agricultural systems—in addition to strategies for managing risk and/or uncertainty—are frustratingly limited in comparison to the rich ethnographic record of how humans have navigated climatic stressors. This article proposes that legumes might provide a new, albeit woefully understudied, vector for potential analyses, especially given their central role in traditional agricultural systems as a buffer against environmental stress. The peculiar agronomic character of legumes, especially among the widely cultivated varieties that are toxic in their unrefined state, could allow for robust hypotheses about agricultural strategies to be tested against our paleoclimate record. Importantly, these hypotheses could be tested against a wide variety of models of human–plant and human–environment interaction, as they could be based on labor costs rather than assumptions of ancient cultural preference. Legumes, however, present particular difficulties as objects of analyses, and therefore some methodological cautions are in order. Consequently, instead of proposing and testing hypotheses, this article seeks instead to inspire future research in relation to our constantly improving data. Full article

Numerous uncertainties persist regarding the differential enrichment mechanisms of shale gas reservoirs in southern China. This investigation systematically examines the sedimentary environments and reservoir characteristics of the Wufeng–Longmaxi formations in the Changning area of the Sichuan Basin, through the integration of comprehensive drilling data, core samples, and analytical measurements. Multivariate sedimentary proxies (including redox conditions, terrigenous detrital influx, basinal water restriction, paleoclimatic parameters, paleowater depth variations, and paleo-marine productivity) were employed to elucidate environmental controls on reservoir development. The research findings demonstrate that during the depositional period of the Wufeng Formation in the Changning area, the bottom water was characterized by suboxic to anoxic conditions under a warm-humid paleoclimate, with limited terrigenous detrital input and strong water column restriction throughout the interval. Within the Longmaxi Formation, the depositional environment evolved from intensely anoxic conditions in the LM1 through suboxic states in the LM3 interval, approaching toxic conditions by the LM2 depositional phase. Concurrently, the paleoclimate transitioned towards warmer and more humid conditions, accompanied by progressively intensified terrigenous input from the LM1-LM6, while maintaining semi-restricted water circulation. Both paleowater depth and paleoproductivity peaked from the Wufeng Formation to the LM1 interval, followed by gradual shallowing of water depth and declining productivity during the LM3–LM6 depositional phases. Comparative analysis of depositional environments and reservoir characteristics reveals that sedimentary conditions exert a controlling influence on multiple reservoir parameters, including shale mineral composition, organic matter enrichment, pore architecture, petrophysical properties (e.g., porosity, permeability), and gas-bearing potential. Full article

Paleoclimate records have long documented the existence of multicentury hydroclimate anomalies in the Altiplano of South America. However, the causes and mechanisms of these extended events are still unknown. Here, we present a climate modeling experiment that explores the oceanic drivers and atmospheric mechanisms conducive to long-term precipitation variability in the southern Altiplano (18–25° S; 70–65 W; >3500 masl). We performed a series of 100-year-long idealized simulations using the Weather Research and Forecasting (WRF) model, configured to repeat annually the oceanic and atmospheric forcing leading to the exceptionally humid austral summers of 1983/1984 and 2011/2012. The aim of these cyclical experiments was to evaluate if these specific conditions can sustain a century-long pluvial event in the Altiplano. Unlike the annual forcing, long-term negative precipitation trends are observed in the simulations, suggesting that the drivers of 1983/1984 and 2011/2012 wet summers are unable to generate a century-scale pluvial event. Our results show that an intensification of the anticyclonic circulation along with cold surface air anomalies in the southwestern Atlantic progressively reinforce the lower and upper troposphere features that prevent moisture transport towards the Altiplano. Prolonged drying is also observed under persistent La Niña conditions, which contradicts the well-known relationship between precipitation and ENSO at interannual timescales. Contrasting the hydroclimate responses between the Altiplano and the tropical Andes result from a sustained northward migration of the Atlantic trade winds, providing a useful analog for explaining the divergences in the Holocene records. This experiment suggests that the drivers of century-scale hydroclimate events in the Altiplano were more diverse than previously thought and shows how climate modeling can be used to test paleoclimate hypotheses, emphasizing the necessity of combining proxy data and numerical models to improve our understanding of past climates. Full article

The lacustrine mudstones and shales of the Triassic Yanchang Formation in the Ordos Basin serve as critical hydrocarbon source rocks. However, previous studies predominantly focus on individual lithologies, with comparative investigations into the sedimentary environments of dark mudstones and black shales remaining relatively limited. The study systematically compares sedimentary environment parameters (e.g., paleoclimate, paleosalinity, paleoredox conditions, paleowater depth, and paleoproductivity characteristics) between mudstones and shales, and how these distinct environmental factors governed the differential enrichment mechanisms of organic matter within the depositional aquatic system has been elucidated. Geochemical proxies (e.g., CIA, Sr/Cu, Rb/Sr, Sr/Ba, V/Ni, U/Th, V/Cr, Rb/Zr, P/Ti, Cu/Ti) reveal marked contrasts: In comparison with the Chang 7 and Chang 8 dark mudstones, the Chang 7 black shales exhibit (1) warmer–humid paleoclimatic regimes, (2) higher paleosalinity, (3) intensely anoxic conditions, (4) deeper paleowater depth, and (5) elevated paleoproductivity. These environmental divergences directly govern the significant total organic carbon content disparity between black shales and dark mudstones. Organic enrichment in the Chang 7 dark mudstones and black shales is primarily controlled by paleoproductivity and paleoredox conditions, with secondary influences from paleoclimate and paleowater depth. Based on the above studies, this research established a differential organic matter enrichment model. This research is of significant importance for guiding oil and gas exploration and development in the Ordos Basin. Full article

Current models of sedimentary environments and organic matter (OM) enrichment for the Lower Cambrian black shales in the Yangtze Platform have not yet incorporated its northern carbonate platform margin where the related research is lacked. This study focuses on the SNZ1 well in the northern carbonate platform margin, utilizing total organic carbon (TOC) content and major and trace element data to reveal the main controlling factors of OM enrichment during the Early Cambrian. The results show that the shale stratum is tentatively ascribed to the Lower Cambrian Stage 3 and that, during its deposition, the redox transitioned from anoxic to suboxic–oxic conditions, the hydrodynamic conditions weakened initially and then strengthened, the primary productivity first increased and then decreased, the paleoclimate shifted from arid–cold to warm–humid conditions, and the terrigenous clastic input gradually diminished. Overall, the OM enrichment is primarily controlled by preservation conditions. By systematically analyzing the data from the intraplatform basin to the deep-sea basin across the Yangtze Block, a model of the sedimentary environments and OM enrichment during the Early Cambrian was suggested. Additionally, this study highlights the intrinsic link between the expansion of oxygenated surface water and the Cambrian explosion. These results provide critical insights for shale gas exploration in this region. Full article

The Yangzhuang Formation of the Mesoproterozoic Jixian System exhibits a well-developed carbonate sedimentary sequence. However, the carbonate cycles within the Yangzhuang Formation and their co-evolution with paleoclimate and paleoceanographic environment changes remain insufficiently studied. This study conducts a systematic investigation of the rhythmic layers of the Yangzhuang Formation within the Yanshan Basin, North China, through major and trace element analysis, rare earth element analysis, inorganic carbon isotope analysis, granulometric analysis, and time series analysis. The results show that the low content of terrigenous clastics (11.2%~32.6%), slow sedimentation rate (2.2–2.5 cm/ka), Mg/Ca molar ratio close to 1 (1.05–1.53), and small fluctuation of δ¹³C_carb (−0.37‰~−0.05‰) in Member 3 of the Yangzhuang Formation constitutes the processes of co-evolution, along with a mid-phase fluctuation. It indicates the stable evolution of the sedimentary environment and slow ocean expansion speed. However, there is a fluctuating characteristic affected by the breakup of the Colombian supercontinent. The chemical and granulometric analysis of the red and gray layers shows that the terrigenous materials are mainly derived from the eolian sediments, with differences in the wind carrying materials. The time series analysis of the dense samples displays the coupling between the rhythm of the red and gray layers, the inorganic carbon isotope cycle, and the 15 ka precessional cycle in the Mesoproterozoic. We conclude that the rhythm of layers is mainly affected by the monsoon change driven by low-latitude solar radiation at that time, and the age of the Yangzhuang Formation is limited to 1550~1520 ± 2 Ma. The study of the Mesoproterozoic sequence using geochemical data from carbonate deposits reveals the underlying mechanism of global co-evolution during this period, providing a basis for understanding the evolution of the Mesoproterozoic Earth system. Full article

The Minghuazhen Formation in the Cangdong Sag of the Bohai Bay Basin is a key sedimentary unit for investigating regional provenance evolution, paleoclimate variations, and hydrocarbon potential in Eastern China. This study integrates mineralogical and geochemical analyses to explore sedimentary characteristics. Techniques include X-ray diffraction (XRD), major/trace element compositions, rare earth element (REE) distributions, and organic carbon content. XRD data and elemental ratios (e.g., Al/Ti, Zr/Sc) suggest a predominant felsic provenance, sourced from acidic magmatic rocks. The enrichment with light rare earth elements (LREE: La–Eu) and notable negative Eu anomalies in the REE patterns support the interpretation of a provenance from the Taihangshan and Yanshan Orogenic Belts. Geochemical proxies, such as the Chemical Index of Alteration (CIA) and trace element ratios (e.g., U/Th, V/Cr, Ni/Co), indicate a warm and humid depositional environment, characterized by predominantly oxic freshwater conditions. Organic geochemical parameters, including total organic carbon (TOC), total nitrogen (TN), and C/N ratios, suggest that organic matter primarily originates from aquatic algae and plankton, with C/N values predominantly below 10 and a strong correlation between TOC and TN. The weak correlation between TOC and total carbon (TC) indicates that the organic carbon is mainly biological in origin rather than carbonate-derived. Although the warm and humid climate promoted the production of organic matter, the prevailing oxic conditions hindered its preservation, resulting in a relatively low hydrocarbon generation potential within the Minghuazhen Formation of the Cangdong Sag. These findings provide new insights into the sedimentary evolution and hydrocarbon potential of the Bohai Bay Basin. Full article

This study focuses on the upper section of the Zhujiang Formation in the Enping Sag of the Zhujiangkou Basin in the South China Sea, investigating the mechanisms by which astronomical orbital cycles drive paleoclimate, sea-level fluctuations, and sedimentary development. In this study, a cyclic stratigraphic analysis was performed using natural gamma-ray logging data and geochemical proxies (Chemical Index of Alteration (CIA); Al₂O₃ content) in combination with depositional noise modeling (DYNOT Dynamic Orbital Tuning Model and ρ1 noise factor). High-resolution time series analysis revealed three key findings: (1) a 15.98–19.09 Ma astronomical timescale was established through the identification of Milankovitch cycles including 405 kyr eccentricity, 100 kyr eccentricity, 40 kyr obliquity, and 20 kyr precession; (2) sea-level changes exhibited 405 kyr eccentricity-driven cyclicity, with high-eccentricity phases corresponding to warm-humid climates and transgressive mudstone deposition, and low-eccentricity phases reflecting arid conditions and regressive sandstone development; and (3) orbital-scale precession modulation regulated sediment source-to-sink processes through climate–sea level coupling. This work provides a quantitative framework for predicting astronomical cycle-controlled reservoirs, offering critical insights for deepwater hydrocarbon exploration in the Zhujiangkou Basin. Full article