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Sedimentary deposits in lakes across the upper Midwest record the co-evolution of climate and biogeochemistry since the retreat of the Laurentide Ice Sheet at the end of the last glacial period. Here, we report on a Holocene lake sediment record from Chub Lake, a shallow (3 m depth) eutrophic lake system in south-central Minnesota. High-resolution elemental data from scanning XRF along with variations in organic matter, carbonate minerals, clastic material, biogenic silica, charcoal, and carbon isotopes reveal internally consistent patterns of hydroclimatic influence on this shallow lake system from 11,300 years BP to present. In particular, authigenic carbonate mineral formation and preservation in Chub Lake appears to be well suited as a moisture proxy beginning around 9700 BP up until ∼2300 BP, when a combination of more humid climates and basin-infilling change the hydrology of Chub Lake. This work emphasizes the importance of evaluating shallow lake sediment records both as important archives of climate proxies and case studies on how changing climates impact aquatic systems. [ABSTRACT FROM AUTHOR]

Theropithecus gelada, the last surviving species of this genus, occupy a unique and highly specialised ecological niche in the Ethiopian highlands. A subdivision into three geographically defined populations (Northern, Central and Southern) has been tentatively proposed for this species on the basis of genetic analyses, but genomic data have been investigated only for two of these groups (Northern and Central). Here we combined newly generated whole genome sequences of individuals sampled from the population living south of the East Africa Great Rift Valley with available data from the other two gelada populations to reconstruct the evolutionary history of the species. Integrating genomic and paleoclimatic data we found that gene‐flow across populations and with Papio species tracked past climate changes. The isolation and climatic conditions experienced by Southern geladas during the Holocene shaped local diversity and generated diet‐related genomic signatures. [ABSTRACT FROM AUTHOR]

Historical documents provide evidence for regional droughts preceding the political turmoil and fall of Beijing in 1644 CE, when more than 20 million people died in northern China during the late Ming famine period. However, the role climate and environmental changes may have played in this pivotal event in Chinese history remains unclear. Here, we provide tree-ring evidence of persistent megadroughts from 1576 to 1593 CE and from 1628 to 1644 CE in northern China, which coincided with exceptionally cold summers just before the fall of Beijing. Our analysis reveals that these regional hydroclimatic extremes are part of a series of megadroughts along the Pacific Rim, which not only impacted the ecology and society of monsoonal northern China, but likely also exacerbated external geopolitical and economic pressures. This finding is corroborated by last millennium reanalysis data and numerical climate model simulations revealing internally driven Pacific sea surface temperature variations and the predominance of decadal scale La Niña-like conditions to be responsible for precipitation decreases over northern China, as well as extensive monsoon regions in the Americas. These teleconnection patterns provide a mechanistic explanation for reoccurring drought spells during the late Ming Dynasty and the environmental framework fostering the fall of Beijing in 1644 CE, and the subsequent demise of the Ming Dynasty. [ABSTRACT FROM AUTHOR]

Marine Isotope Stage 3 (MIS 3) is characterized by significant millennial-scale climatic oscillations between cold stadials and mild interstadials, which presents a valuable case for understanding hydrological response to abrupt climate change. Through a set of coupled model simulations, our results broadly show an antiphased interhemispheric change in land monsoonal precipitation during the present-day relative to MIS 3 interstadial and the stadial–interstadial transition, with a general decrease in the Northern Hemisphere but an increase in the Southern Hemisphere. The antiphased pattern is largely caused by the change in orbital insolation during the present-day relative to MIS 3 interstadial, whereas by the weakened Atlantic meridional overturning circulation during the interstadial–stadial transition. However, there are obvious discrepancies in precipitation response and underlying mechanisms among individual monsoon domains and across different periods. Based on the moisture budget analysis, we indicate that the dynamic factor mainly explains the decreased monsoonal rainfall in the Northern Hemisphere during the present-day relative to the MIS 3 interstadial, whereas the thermodynamic term is largely responsible for the increased precipitation in the Southern Hemisphere. In contrast, the dynamic factor plays an important role in the variation of precipitation over all the monsoon zones from the MIS 3 interstadial to stadial states, with the thermodynamic term mainly contributing to the decreased tropical monsoonal precipitation in the colder Northern Hemisphere. Our results help improve the understanding of global monsoon variations under intermediate glacial climate conditions and shed light on their behaviors under potentially rapid climate change in the future. [ABSTRACT FROM AUTHOR]

The sediments from the Babouri-Figuil intracontinental Basin were investigated by major and trace elements geochemistry and paleontological analysis to infer their Paleoenvironment and paleoclimate evolution and metallogenic implication of an approximately 120-m thick sequence along the Mayo Louti River in this basin. The geochemical compositions revealed that the studied materials are mainly composed of Shales associated with Fe-sands, Wacke and Litharenite. These sediments show high ΣLREE/ΣHREE ratios (Σlight rare earth elements/Σheavy rare elements ratios: 5.16 to 10.49); weak negative and positive Eu anomaly (Eu/Eu* = 0.84 to 1.28) and Ce anomaly (Ce/Ce* = 0.93 to 1.10); Al2O3/TiO2 ratios (17.02–28.16); Th/Co ratios (0.23–1.36). These features, together with the Ce vs La/Yb, Zr vs TiO2 and La/Sc vs Th/Co plots, indicate that the sediments are derived mainly from felsic rocks associated with intermediate composition rocks. The CIA and CIX (Chemical Index of Alteration: respectively 48.02 to 60.97 and 62.69 to 71.42) suggest that the source rocks have experienced low to moderate recycling and sorting and weathering. The SiO2 vs. Al2O3 + K2O + Na2O, C-values, Sr/Ba, and Rb/Sr plots, and palynological content dominated by Gymnosperm pollens such as Classopollis sp. and Araucariacites sp., associated with single spores such as Cicatricosisporites sp indicate mainly semi-arid/humid to arid climate during the period of deposition, fluctuating from the bottom to the top of the sequence. The Sr/Ba values ranging from 0.78 to 12.23, suggest a fluctuating and sometimes high salinity (Hypersaline milieu). The presence of numerous tetrads to dyads and wood trunks indicates a lacustrine or swampy environment surrounded by vegetation, and the Ni/Co (1.75 to 4.14) and U/Th (0.10 to 0.64) ratios are consistent with oxic conditions. The discriminant function-based multidimensional tectonic diagrams show an arc-collisional setting, which is consistent with the Precambrian geological history of the study area, and indicate the unreworked and unsorted character of these sediments. The Al/Si ratio shows positive correlation with CIA (R2 = 0.59), Th (R2 = 0.37), Zr (R2 = 0.47), Hf (R2 = 0.51), Na (R2 = 0.39), K (R2 = 0.73) and negative correlation with Ca (R2 = 0.32) and Mg (R2 = 0.30). The positive correlation with K, Hf, Na, Zr, and Th from detrital origin and negative correlation with Ca and Mg from chemical origin could suggest the geochemical composition control of grain size as in the Amazonian floodplain deposits. The studied samples are essentially terrigenous and very weakly metalliferous. [ABSTRACT FROM AUTHOR]

A synthesis of field geological and archaeological surveying, as well as near-surface stratigraphy, provides new insights into the late Quaternary history of this region. We find a long series of alluvial, colluvial, playa, and aeolian deposits that show a complicated history of changes in the late Quaternary climate and environment. In the current study, we summarize the results of a geoarchaeological study that focused on the entire range of landscapes and associated landforms along the fringe of the Libyan Plateau at Umm Dabadib, Kharga Oasis, in the Western Desert of Egypt. We also determined the distribution of the cultural materials of prehistoric sites in different geomorphic settings, including playas, wadis, and dune fields. [ABSTRACT FROM AUTHOR]

Tropical carbonate systems are valuable archives of paleoenvironments, as the carbonate growth is intimately affected by water depth and climatic conditions. Geochemical data from the Burdigalian interval in IODP Site U1468 in the Maldives, northern Indian Ocean, were integrated with sedimentological and paleontological data for a more detailed reconstruction of depositional history. Generally, the Sr/Ca values of slope sediments record highstand progradation in both sequence unit and whole Burdigalian interval, while the absence of higher Sr/Ca ratio close to the sequence boundary during the early Burdigalian could be related to the erosion of deeper-water sediments due to the activity of bottom current. From 20.5 to 19.1 Ma and from 17.9 to 17.2 Ma, nutrient level and productivity were moderately elevated due to the terrigenous input by the intensified South Asian Proto-Monsoon, which also helped cause more reducing conditions in the distal slope. Moreover, increased nutrient level facilitated the growths of calcareous algae and sponges, while it was not favorable for coral development. The elevated nutrient level, higher sea level, and monsoon-induced current contributed to the backstepping of the outer margin during the late Burdigalian. Our study shows an example on how a tropical carbonate platform evolved in response to the interplay of sea-level and paleoclimatic conditions. Findings are expected to be applicable to other tropical carbonate platforms. [ABSTRACT FROM AUTHOR]

Premise: Leaf mass per area (LMA) is a widely used functional trait in both neobotanical and paleobotanical research that provides a window into how plants interact with their environment. Paleobotanists have used site‐level measures of LMA as a proxy for climate, biome, deciduousness, and community‐scale plant strategy, yet many of these relationships have not been grounded in modern data. In this study, we evaluated LMA from the paleobotanical perspective, seeking to add modern context to paleobotanical interpretations and discover what a combined modern and fossil data set can tell us about how LMA can be best applied toward interpreting plant communities. Methods: We built a modern data set by pulling plant trait data from the TRY database, and a fossil data set by compiling data from studies that have used the petiole‐width proxy for LMA. We then investigated the relationships of species‐mean, site‐mean, and site‐distribution LMA with different climatic, phylogenetic, and physiognomic variables. Results: We found that LMA distributions are correlated with climate, site taxonomic composition, and deciduousness. However, the relative contributions of these factors are not distinctive, and ultimately, LMA distributions cannot accurately reconstruct the biome or climate of an individual site. Conclusions: The correlations that make up the leaf economics spectrum are stronger than the correlations between LMA and climate, phylogeny, morphospace, or depositional environment. Fossil LMA should be understood as the culmination of the influences of these variables rather than as a predictor. [ABSTRACT FROM AUTHOR]

Ceratophryid frogs inhabit the lowlands of South America and exhibit greater diversity in the semiarid Gran Chaco. The presence of Ceratophryidae dates back to the late Miocene on the eastern slopes of the Andes in Argentina. Herein, we describe the remains of Ceratophrys from late Miocene of Palo Pintado Formation (Salta, Argentina). Fragmentary bones were recovered from the base of the unit in beds dated between 8 and 7.7 million years ago. The specimen IBIGEO-P141 exhibits the fusion of dentary and mentomeckelian bones forming a fang, a sharp-edged lower jaw, and sculptured bones as Ceratophryidae. The granular pattern of sculpturation, differences between pars facialis and pars dentalis of maxillary, and the shape of lower jaw, support its assignment to the genus Ceratophrys. Combined bioclimatic data and geographic distribution of living Ceratophrys indicate a strong influence of precipitation variables in the distribution of these frogs with adaptations to survive long dry periods. These facts suggest a seasonal rainfall with a well-defined dry season during the deposition of lower levels of Palo Pintado Formation. The palaeoclimatic conditions resemble those occurring in the actual semiarid Chaco, and reveal that the historical geographic distribution of Ceratophryidae was retracted eastward due to the Andean uplift. [ABSTRACT FROM AUTHOR]

This paper completes the examination of results of the study of lithogeochemical characteristics of a pilot collection of the Riphean–Vendian sandstones, siltstones, and claystones (last one based on the interpretation of results) in Belarus. Data on the age of detrital zircon published in recent years suggest that Upper Precambrian rocks of this region were sourced from the Osnitsk–Mikashevichi and the Trans-Scandinavian igneous belts, the Volyn–Brest large igneous province, rapakivi granites, as well as various rock associations of Sarmatia, Danopolonian orogen and Svecofennides. Based on the lithogeochemical characteristics, the distribution of data points of the studied clastic rocks on discriminant diagrams provides insight into the possible provenance, paleogeodynamic, paleogeographic, and paleoclimatic settings and suggests several conclusions. The considered Riphean–Vendian stratons in Belarus are composed mainly of erosion products of within-plate granitoids, as well as various island-arc and syncollisional felsic igneous rocks. The share of erosion products of mafic rocks among them generally does not exceed 30%. It is significant mainly in the Volyn Group rocks (erosion products of the Volyn–Brest large igneous province), as well as in some samples of the Nizov, Selyavy, and Kotlin formations (fragments of mafic rocks from other provenances?). The source-to-sink transport was accomplished mainly by large rivers. Paleogeodynamic settings varied from quite active to quite passive. The paleoclimate in catchment areas was most likely arid/semiarid in the Riphean. In the Vendian, it was humid and varied from subtropical in the Early Vendian (except the Glusk Formation) to tropical in the Late Vendian. The obtained results also make it possible to show some peculiarities of the known methods and techniques of paleoclimate reconstruction. [ABSTRACT FROM AUTHOR]

Estimation of climate sensitivity is fundamental to assessing how global climate will warm as atmospheric CO2 ${\mathrm{C}\mathrm{O}}_{2}$ concentration increases. Geological archives of environmental change provide insights into Earth's past climate, but the incomplete nature of paleoclimate reconstructions and their inherent uncertainties make estimation of climate sensitivity challenging. Thus, quantifying climate sensitivity and assessing how it changed through geological time requires statistical frameworks that can handle data uncertainties in a principled fashion. Here we demonstrate some of the hurdles to estimating climate sensitivity, with a focus on current statistical techniques that may underestimate both climate sensitivity and its associated uncertainty. To solve these issues, we present a Bayesian error‐in‐variables regression model, which can yield estimates of climate sensitivity without bias. The regression model is flexible and can account for data point uncertainties with a known parametric form. The utility of this approach is demonstrated by estimating specific climate sensitivity with uncertainty for the Eocene. Plain Language Summary: As atmospheric CO2 ${\mathrm{C}\mathrm{O}}_{2}$ increases due to human activities, the Earth will warm. But how much warming can be expected? Climate sensitivity describes how much global average surface temperature will warm with a given increase in atmospheric CO2 ${\mathrm{C}\mathrm{O}}_{2}$. While this is a simple definition, estimating climate sensitivity is difficult because Earth's climate system is complex with a number of poorly understood interacting parts. One approach to estimating climate sensitivity is to quantify how Earth's climate changed as a result of variations in atmospheric CO2 ${\mathrm{C}\mathrm{O}}_{2}$ through geological time. This information is invaluable, but it is patchy and has large uncertainties that make estimating climate sensitivity challenging. In particular, existing statistical techniques may underestimate climate sensitivity and, thus, underestimate future warming. In this paper we present an alternative approach to determining climate sensitivity that overcomes the underestimation problem and demonstrate its performance using geological data from the Eocene epoch. Key Points: We demonstrate that regression‐based estimates of specific climate sensitivity may be biased toward zero because of data uncertaintiesA Bayesian error‐in‐variables approach is developed that accounts for data uncertainties in regression‐based climate sensitivity estimatesEocene specific climate sensitivity is estimated to demonstrate the utility of Bayesian error‐in‐variables regression [ABSTRACT FROM AUTHOR]

The hydrogen isotopic compositions of leaf‐wax n‐alkanes (δDalk) and n‐alkanoic acids (δDacid) reflect ambient climatic conditions (including precipitation δD values, δDprecip). However, the understanding of climatic conditions of exactly which period (i.e., early or entire period of the leaf's lifespan) these biomarkers preserve is still evolving. Previous studies on the δDalk and δDacid values, done only in extra‐tropical regions, mostly indicate that δDalk values are biased toward the early growing season whereas δDacid values are not biased toward any season. To decipher the seasonal bias in δDalk and δDacid records from tropics, we conducted a long‐duration experiment wherein deciduous and evergreen species were grown using normal water (δD = −2‰) during early stages of the leaf growth and later using isotopically labeled water (δD = 1,000‰). Our experiment revealed (a) in deciduous and evergreen species, δDalk and δDacid values reflect δDprecip during early stages of the leaf growth, (b) synchronous synthesis of n‐alkanes and n‐alkanoic acids, and (c) in deciduous species, minor incorporation of the previous year's photosynthates in leaf wax pool of the current year's mature leaves. Our study suggests that δDalk and δDacid records in the tropics are biased toward the climatic conditions prevailing during early stages of leaf growth. This bias should be considered while comparing the δDprecip values generated from leaf wax proxy records and isotope‐enabled atmospheric circulation models. Plain Language Summary: The hydrogen isotopic composition of leaf wax n‐alkanes and n‐alkanoic acids preserved in sediments have been used extensively for reconstructing past climate variability. However, whether these records reflect a climate of a specific season or an entire year is not known. In our experiment, we grew various tropical plants using normal water during early growing season and heavy water during later growing season. Lack of isotopic signal associated with the heavy water in leaf wax compounds suggested that the bulk of leaf wax production occurred during the early growing season of the leaves. As the hydrogen isotopic composition of the leaf wax compounds reflects ambient climatic conditions, our results suggested that the hydrogen isotope record of tropical leaf wax compounds reflects the climatic conditions prevailing during the early stages of leaf growth. Key Points: Hydrogen isotope records of leaf wax n‐alkane and n‐alkanoic acid from the tropics reflect climatic conditions during the early leaf growthBoth deciduous and evergreen leaf wax hydrogen isotope records are biased toward the early stages of the leaf growthThis bias should be considered while comparing the hydrogen isotope of precipitation generated from climate models and leaf wax records [ABSTRACT FROM AUTHOR]

Paleogene age deposits east of the Fifteenmile River, northwest of Dawson City, Yukon, Canada preserve a diverse high‐latitude fossil flora. Here, we provide new data on the age of the fossil site based on laser ablation–inductively coupled plasma–mass spectrometry (LA‐ICP‐MS) U‐Pb dating of tephra zircons, paleobotanical paleoclimate reconstructions, and growing season length estimates based on photoperiod. These new data indicate an age of the Fifteenmile River fossil locality as late middle Eocene and likely within the Middle Eocene Climatic Optimum episode. The paleoflora‐based paleoclimate reconstruction indicates the region was relatively wet and warm with non‐freezing winters, but also experienced seasonal dryness, with an approximate 7 months long growing season as suggested by photoperiod. We interpret this paleoclimate as summer dry and winter wet—a climate analogous to modern day warm Mediterranean climates in the Köppen‐Geiger climate classification system. These findings provide a new perspective on the past climate and environment of high‐latitude ecosystems during warm greenhouse intervals and contribute to our understanding of the Earth's climate history and its potential future changes. Key Points: New U‐Pb data show the Fifteenmile River fossil flora age is late middle Eocene, potentially within the Middle Eocene Climatic OptimumWest central Yukon had a warm Mediterranean climate, with wet, mild winters and a distinct summer‐dry season during the late middle EoceneGrowing season length at high latitudes during greenhouse intervals would be determined by photoperiod, not temperature [ABSTRACT FROM AUTHOR]

Marine Isotope Stage (MIS) 5c, between ~106 000 and ~93 000 years ago, represents an important warm period in which the current anthropogenic warming can be contextualized. Although viewed as a pronounced interstadial, its climate expression is regionally disparate, with different regions on Earth showing evidence of either cooler or warmer conditions than modern‐day. It is therefore important to expand temperature reconstructions to different regions on Earth to gain a better picture of climate dynamics during MIS 5c. In Alaska, there are no quantitative temperature reconstructions for MIS 5c, limiting our knowledge of temperature changes in this climatically sensitive high‐latitude region. Here, we fill this gap by providing the first quantitative temperature estimates from MIS 5c in Alaska using hydrogen isotopes of fluid inclusions in precisely dated speleothems. We find that regional temperatures during MIS 5c were within error of the modern‐day reference period (1929–1989 ce) temperatures, possibly representing the most recent time period that regional temperatures were as high as modern‐day. [ABSTRACT FROM AUTHOR]

We compare hydrogen isotopic measurements of long-chain leaf-wax n-alkanes (δ2Hw; C27, C29, and C31) from Martin Lake, Indiana, USA, with a calcite-based reconstruction of the oxygen isotopic composition of precipitation (δ18Op) from the same lake. We observe stable and high δ2Hw during the Common Era (last 2000 years), which we interpret as growing-season precipitation originating mainly from the Gulf of Mexico and Atlantic. During the Little Ice Age (LIA; 1200–1850 CE), δ2Hw values increased by 3–8 ‰, concomitant with a significant decrease in δ18Op values by up to 12.5 ‰. Multiple proxy records for this time indicate persistent growing-season drought. We interpret these relatively high δ2Hw values, as compared to the δ18Op values, as a signal of low relative humidity that resulted in an 2H enrichment in plant source water resulting in high δ2H values through enhanced plant water and/or soil evaporation. These results support the occurrence of low humidity conditions during the LIA in the midcontinental USA that also contributed to the marked decline of regional pre-Columbian Mississippian populations. [ABSTRACT FROM AUTHOR]

Rates of land surface processes provide insights into climatic and tectonic influences on topography. Bedrock incision rates are estimated by dating perched landforms such as strath terraces, assuming a constant bedrock incision rate from terrace abandonment to the next terrace level or present river level. These estimates express biases from the stochastic nature of sediment and water discharge in controlling river incision as well as from using a mobile channel elevation as a reference frame, leading to different incision rates when calculated over different timeframes. We introduce a 1‐D model incorporating fluvial mechanics, tectonics, sediment, and climate variability to predict these biases and assess their sensitivity to climate and tectonics. Findings suggest biases intensify under highly variable climates and slow rock uplift, with climate periodicity being a primary control for our modeled scenarios. Our model provides a mechanism to improve river incision measurement uncertainty, impacting paleoclimate and tectonic geomorphology reconstructions. Plain Language Summary: Geomorphologists often measure how fast rivers erode bedrock over time by dating river terraces that have been uplifted to be higher than the elevation of the modern river channel. This helps us learn how landscapes evolve and about what past climates were like over long timescales. But this method is complicated by the fact that rivers do not erode rocks at a steady rate and the elevation of the channel surface above which we measure terrace height changes over time. We present a numerical model that predicts how these terraces develop under different climates and rates of rock uplift. Model results imply that measurements of long‐term river incision are most susceptible to temporal bias in regions experiencing highly variable paleo‐climate and slow rock uplift. Our model helps us make better measurements of river erosion and understand how climate and rock uplift shape landscapes. Key Points: We present a numerical model that reproduces biases in rates of river incision measured from strath terracesWe find that these measurement biases are the strongest when climates are highly variable and rock uplift is slowUnderstanding bedrock incision measurement biases allows for bias correction in field studies and improves data comparability [ABSTRACT FROM AUTHOR]

Our solar system's path has recently been shown to potentially intersect dense interstellar clouds 2 and 7 million years ago: the Local Lynx of Cold Cloud and the edge of the Local Bubble. These clouds compressed the heliosphere, directly exposing Earth to the interstellar medium. Previous studies that examined climate effects of these encounters argued for an induced ice age due to the formation of global noctilucent clouds (NLCs). Here, we revisit such studies with a modern 2D atmospheric chemistry model using parameters of global heliospheric magnetohydrodynamic models as input. We show that NLCs remain confined to polar latitudes and short seasonal lifetimes during these dense cloud crossings lasting ∼105 years. Polar mesospheric ozone becomes significantly depleted, but the total ozone column broadly increases. Furthermore, we show that the densest NLCs lessen the amount of sunlight reaching the surface instantaneously by up to 7% while halving outgoing longwave radiation. Plain Language Summary: As the Solar System moves through the interstellar medium, it encounters different astrophysical environments. By tracing back the path of the Sun, two possible crossings of dense interstellar clouds 2 and 7 million years ago have been identified. These clouds are dense enough to compress the solar wind to inside of Earth's orbit, exposing Earth's atmosphere to interstellar gas. Previous studies that explored terrestrial climate changes due to these event argued for a global cooling effect that could trigger an ice age. In this study, we revisit this topic with a modern computational atmospheric chemistry model. We find that high‐altitude water significantly enhances the density and coverage of noctilucent clouds (NLCs) near the mesopause. In contrast with previous studies, this effect is neither permanent nor global, though some denser NLCs may still block up to 7% of sunlight from reaching Earth's surface. Furthermore, HOx compounds greatly deplete mesospheric ozone. We find for the first time that this mesospheric ozone decrease allows for a stratospheric ozone increase, resulting in an increase in the total ozone column. In order to assess the complete global climate response to these events, a more complete 3D model is required. Key Points: As a result of colliding with interstellar clouds 2 and 7 million years ago, Earth's upper atmosphere received an abundance of hydrogenBy converting interstellar hydrogen to water in the lower thermosphere, thick noctilucent clouds would have formedHOx compounds could have depleted mesospheric ozone by up to 99%, though the total ozone column generally increases [ABSTRACT FROM AUTHOR]

The 72‐foot sailing yacht Eugen Seibold is a new research platform for contamination‐free sampling of the water column and atmosphere for biological, chemical, and physical properties, and the exchange processes between the two realms. Ultimate goal of the project is a better understanding of the modern and past ocean and climate. Operations started in 2019 in the Northeast Atlantic, and will focus on the Tropical Eastern Pacific from 2023 until 2025. Laboratories for air and seawater analyses are equipped with down‐sized and automated state‐of‐the‐art technology for a comprehensive description of the marine carbon system including CO2 concentration in the air and sea surface, pH, macro‐, and micro‐nutrient concentration (e.g., Fe, Cd), trace metals, and calcareous plankton. Air samples are obtained from ca. 13 m above sea surface and analyzed for particles (incl. black carbon and aerosols) and greenhouse gases. Plankton nets and seawater probes are deployed over the custom‐made A‐frame at the stern of the boat. Near Real‐Time Transfer of underway data via satellite connection allows dynamic expedition planning to maximize gain of information. Data and samples are analyzed in collaboration with the international expert research community. Quality controlled data are published for open access. The entire suite of data facilitates refined proxy calibration of paleoceanographic and paleoclimate archives at high temporal and spatial resolution in relation to seawater and atmospheric parameters. Plain Language Summary: The new research sailing yacht Eugen Seibold (ES) enables clean, contamination‐free sampling of air and seawater to better understand the interactions between ocean and climate. For example, the oceans remove increasingly less carbon dioxide (CO2) from the atmosphere the more saturated they are with CO2 (ocean acidification). However, a detailed systematic understanding of air‐sea exchange processes remains to be developed. We analyze air and seawater as well as the exchange of greenhouse gases and other substances such as aerosols and soot (black carbon) between air and seawater at high resolution using modern materials and technologies. Scaled‐down, energy‐efficient, and automated probes developed over the past decade are being used to measure around 50 different characteristics of the marine environment. The work deck at the stern of the boat allows the use of custom‐made water samplers and plankton nets to study the ocean to below 1,000 m depth. In addition, the new data enables a better understanding of past ocean archives, such as the marine plankton accumulated in seafloor sediments, to reconstruct past climate changes. From 2019 to 2022, the S/Y ES sailed in the eastern North Atlantic and will operate in the tropical eastern Pacific until 2025. Key Points: New research platform for contamination‐free sampling of the water column and atmosphere of biological, chemical, and physical propertiesComprehensive marine geochemical analyzes including carbon (e.g., CO2) in air and sea surfaceProxy calibration of paleoclimate archives at high temporal and spatial resolution in relation to seawater and atmospheric parameters [ABSTRACT FROM AUTHOR]

The oxygen isotope ratio 18O/16O (expressed as a δ18OVSMOW value) in marine sedimentary rocks has increased by ~8‰ from the early Paleozoic to modern times. Interpretation of this trend is hindered by ambiguities in the temperature of formation of the carbonate, the δ18Oseawater, and the effects of postdepositional diagenesis. Carbonate clumped isotope measurements, a temperature proxy, offer constraints on this problem. This thermometer is thermodynamically controlled in cases where carbonate achieves an equilibrium internal distribution of isotopes and is independent of the δ18O of the water from which the carbonate grew; therefore, it has a relatively rigorous chemical-physics foundation and can be applied to settings where the δ18O of the water is not known. We apply this technique to an exceptionally well-preserved Ordovician carbonate record from the Baltic Basin and present a framework for interpreting clumped isotope results and for reconstructing past δ18Oseawater. We find that the seawater in the Ordovician had lower δ18Oseawater values than previously estimated, highlighting the need to reassess climate records based on oxygen-isotopes, particularly where interpretations are based on assumptions regarding either the δ18Oseawater or the temperature of deposition or diagenesis. We argue that an increase in δ18Oseawater contributed to the long-term rise in the δ18O of marine sedimentary rocks since the early Paleozoic. This rise might have been driven by a change in the proportion of high- versus low-temperature water-rock interaction in the earth's hydrosphere as a whole. [ABSTRACT FROM AUTHOR]

Radiocarbon and uranium-thorium dating of microbialites and penecontemporaneous cements in a microbialite mound at Death Point at Lakeside, Utah, on the shore of Great Salt Lake, Utah, call for a revision of the Lake Bonneville hydrograph. At about 30,000 cal yr BP, the lake experienced an abrupt rise of about 20 m, then dropped back down to levels near or slightly higher than the modern average elevation of Great Salt Lake. Over the ensuing ~6000 yr the lake experienced a series of fluctuations, up to levels a few tens of meters higher than the modern average Great Salt Lake, then down again. The exact timing and amplitudes of those fluctuations are not known, but importantly, the lake did not rise to levels near the Stansbury shoreline (~80 m higher than Great Salt Lake) until after about 24,000 cal yr BP. After the Stansbury shoreline, the lake rose almost 200 m to its highest level at the Bonneville shoreline by about 17,500 cal yr BP. This interpretation is different from previously published hydrographs, many of which show a relatively steady rise to near the Stansbury shoreline between 30,000 and 25,000 cal yr BP. [ABSTRACT FROM AUTHOR]

The Eocene-Oligocene transition (EOT) marked a rapid global cooling event, often considered as the beginning of the modern icehouse world. Influenced by various factors, including tectonic activity and paleogeographic settings, the terrestrial records indicate a diverse response of fauna and vegetation to this global event. We examined nine macrofossil assemblages from seven fossil localities on the southeastern margin of the Tibetan Plateau and from the mid-latitudinal Europe ranging from the latest Bartonian and Priabonian (37.71–33.9 Ma) to the Rupelian (33.9–27.82 Ma). Our aims were to trace and compare the vegetation history of both regions in the late Eocene and early Oligocene. The results show that both regions experienced changes in vegetation composition in response to climate change, characterized by a decrease in the percentages of broad-leaved evergreen elements and distinctive changes in general vegetation types. A general change in the overall vegetation type from subtropical broad-leaved evergreen forests in the late Eocene to temperate broad-leaved mixed deciduous evergreen forests, or mixed mesophytic forests, in the early Oligocene is recognized in both regions. The results indicate a clear change in leaf architecture, leaf margin states, and secondary venation types in the mid-latitudinal Europe, while the results from the south-eastern margin of the Tibetan Plateau show a distinct reduction in leaf size. Our data suggest that both global and regional factors played key roles in shaping the vegetation in the two regions. [ABSTRACT FROM AUTHOR]

Organic geochemical and stable isotope records of Oligocene and late Miocene–Pliocene sediments from IODP hole U1501C and Pliocene–Pleistocene sediments from U1499A of South China Sea (SCS) were studied to investigate clock sources of organic matter and carbonates and their spatiotemporal variations with East Asian climatic variability. Geochemical data was constrained using shipboard information. CaCO3 and total organic carbon contents (wt%) varied between 1.32 to 56.52 and 0.12 to 1.13, respectively. δ13Ccarb, δ18Ocarb and δ13Corg ranged from −4.89 to 1.98‰, −5.54 to 1.96‰, and −24.66 to −28.13‰, respectively. Contributions from mixed sources of carbon were observed in the Oligocene, while the late Miocene–Pleistocene exhibited terrestrial dominance. Early Oligocene carbonate, low and higher TOC are attributed to the opening of SCS, increased terrigenous input, and prevalence of cooler climate. Stable isotopes suggest the expansion of the marine environment and the probable dawning of the East Asian Winter Monsoon (EAWM) during the Oligocene. The late Oligocene marked a transition to a warmer climate. The strengthening of EAWM since the late Miocene is indicated by moderate organic carbon and high carbonates with enriched isotopes. Glacial low sea levels and higher terrestrial inputs increased TOC, while dissolution affected late Plio–early Pleistocene carbonates. Higher carbonates and productivity since the mid-Pleistocene were influenced by alternate weakening and strengthening of EAWM. Research highlights: Organic matter, carbonates, C and O isotopes from Oligocene and late Miocene–Pleistocene sediments, northern SCS. Productivity in the South China Sea fluctuated, being low during the Oligocene, with a subsequent increase since the late Miocene. δ13Corg and δ13Ccarb indicate cold climatic conditions and probable winter monsoon signatures since the early Oligocene, transitioning to warmer conditions during the late Oligocene. During the late Miocene (~8–5.6 Ma), deep-water circulation and intensified winter monsoons led to higher productivity. Pliocene sediments (since ~5.6 Ma) showed signs of climatic cooling, sea level fluctuations, and enhanced winter monsoons with carbonate dilution. The Plio-Pleistocene period witnessed glacial and interglacial cycles reflecting changing monsoon intensities. [ABSTRACT FROM AUTHOR]

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East Asia is a major source of dust accounting for 20% of the global dust emission. Work on reconstructing past changes in dust transport in East Asia is complicated by difficulties in distinguishing local sedimentation from aerial material and lack of suitable material for age determination. Here, we address these issues and present a new dust proxy record from Lake Motosu, located on the Pacific side of Japan. The record is anchored by a high‐quality tephra and radiocarbon chronology. Because Lake Motosu is situated in a quartz‐free basaltic volcanic province, all quartz deposited in the lake is likely to be aerially sourced, and variations in quartz content should reflect past changes in dust transport. Our new record detects a low dust deposition event from 3.0 to 2.0 ka. This event corresponds to elevated sea surface temperature in the Sea of Japan and climate conditions similar to a negative phase of the Arctic Oscillation, indicating an association with the weakened Westerlies and with less frequent dust storms in the source region. The increase in spatial resolution of past dust transport reconstructions will further improve our understanding of the mechanism related to dust emission from East Asia. Plain Language Summary: One potential proxy for understanding past changes in atmospheric conditions is aeolian dust. The climate variability links between non‐contiguous geographic regions and strong constraints on geological ages are required to better contribute to the understanding of dust transport. Here, the dust deposition history of the past 8,000 years at Lake Motosu was obtained by quantitative X‐ray diffraction analysis to determine the amount of quartz in the sediments. There is no local source of quartz to Lake Motosu, so we consider that quartz is transported to the lake in the atmosphere. The amount of dust deposition to the Lake Motosu has persistently decreased between 3 and 2 thousand ago. This sustained decrease in dust deposition may be caused by conditions similar to a negative phase of the Arctic Oscillation. This interpretation is consistent with other proxy records from East Asia. Key Points: Dust deposition history of the past 8 kyr at Lake Motosu was obtained by quantifying quartz amount by X‐ray diffraction analysisReduced amounts of dust accumulation are recognized between 3 and 2 ka, suggesting the Westerlies were away from Lake MotosuClimate conditions similar to a negative phase of the Arctic Oscillation may be the cause of the sustained decrease in dust deposition [ABSTRACT FROM AUTHOR]

Copyright of Acta Scientiarum Naturalium Universitatis Pekinensis is the property of Editorial Office of Acta Scientiarum Naturalium Universitatis Pekinensis and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

The lithofacies and pedogenic features in the Late Oligocene–Early Pleistocene formations provide evidence of changing paleoclimate in the northeastern Sahara region. The strata of the Katkut Formation and the lower Member of the Madamud Formation consist predominantly of coarse and fine-grained siliciclastic lithofacies deposited by braided and sinuous streams that formed under the influence of humid paleoclimate during the Late Oligocene–Late Miocene time. Paleosol horizons with mature calcretes in the overlying upper member of the Madamud Formation suggest increasing aridity by the end of Late Miocene through Pliocene time. This trend of aridification continued during the Early Pleistocene lacustrine deposition of Issawia and Armant formations, as indicated by the predominance of palustrine carbonates displaying different pedogenic features. The climate change may have resulted from the southward movement of Asian monsoons and the uplifts of the Red Sea Mountain chains, as the African continent drifted northeastward. This paleoclimate transition generated variations in basin sedimentation rates that were controlled by base level and tectonics. [ABSTRACT FROM AUTHOR]

Cr(VI) is a carcinogen with proven mutagenic and genotoxic effects. The effects of the depositional environment (e.g., paleoweathering, paleoclimate, and paleoredox condition) on Cr enrichment in non-ultramafic aquifer solids are unclear. In this study, we presented the sedimentary characteristics of a borehole from a typical non-ultramafic aquifer with high Cr groundwater in Jingbian, central Ordos Basin, China. Chromium was enriched in the K1h sandstone aquifer, especially at depths of 400–500 m, with the highest value of mass transport coefficient (τAl,Cr) up to 92.13% and τAl,Fe up to 33.5%. The provenance of aquifer Cr was predominantly intermediate and felsic igneous rocks with a mafic rock mixture. This mafic source was inferred from Cr-rich granodiorite and mafic/ultramafic rocks in the Yinshan (Daqingshan–Wulashan) Block, northern Ordos Basin. The Cr-rich aquifer in K1h was developed due to a moderate chemical index of alteration (CIA) (mean, 56.7) under relatively warm and humid paleoclimate, as evidenced by high CIA-temperature (CIA-Temp) (mean, 6.79 °C) and paleoclimatic index values (mean, 0.40). Fe–Mn redox cycling in the oxic to suboxic environments contributed to aquifer Cr accumulation. Using path analysis, we identified that paleoclimate created favorable weathering conditions and enrichment of Fe contributed to the formation of high-Cr aquifers. The study reveals the formation of positive Cr anomalies in non-ultramafic aquifers, which is the potential source of groundwater Cr, and highlights the effects of depositional factors on Cr accumulation during aquifer deposition or early diagenesis. It can provide new insights into the natural processes of high-Cr sediments occurring in non-ultramafic aquifers. [ABSTRACT FROM AUTHOR]

The Sichuan Basin, located in southwestern China, is considered the primary producing area for shale gas development in the country. Its rich shale gas reserves have made it a significant contributor to China’s energy production. Within the Sichuan Basin, northeast Sichuan has emerged as a region of particular interest for shale gas development. In order to investigate the controlling factors and enrichment patterns of organic matter-rich shales from the Upper Ordovician Wufeng Formation-Lower Silurian Longmaxi Formation in northeast Sichuan, inductively coupled plasma mass spectrometry (ICP–MS) was used to analyze 14 shale samples from the Wufeng Formation-Longmaxi Formation in northeast Sichuan. Combined with the characteristics of logging curves, the sedimentary system, redox conditions, terrestrial debris input, primary productivity, and paleoclimate relationship of the Wufeng Formation to the Longmaxi Formation were explored. As a result, three third-order sequences (SSQ1, SSQ2, and SSQ3) were identified, and the sea level experienced a process from high-low-high-low, which, in combination with the shale elemental parameters of w(V)/w(Cr), w(V)/w(V+Ni), w(Ni)/w(Co), w(Sr)/w(Cu), w(Sr)/w(Ba), and T (℃), indicated that the Wufeng Formation-Longmaxi Formation underwent an oxidized-poorly oxygenated-anoxic reduced-poorly oxygenated-oxidized freshwater environment; the climate has undergone a warm-humid, dry-cold, warm-humid, dry-cold, warm-humid evolution, and the temperature has gone through the process of decreasing – increasing – decreasing – increasing. The organic matter enrichment pattern of the Wufeng Formation-Longmaxi Formation in northeast Sichuan can be divided into a Ⅲ stage pattern. Stage Ⅰ, the depositional period from the Wufeng Formation to the bottom of the Longmaxi Formation, is a stage of gradual increase in organic carbon; stage Ⅱ, the depositional period of the middle part of the Longmaxi Formation, is a stage of enrichment of organic carbon (sweet-spot member); and stage Ⅲ, the depositional period of the upper part of the Longmaxi Formation, is a stage of gradual decrease in organic carbon. It is expected to provide a basis for the exploration of shale gas in northeast Sichuan, and the next step will be to carry out research on the resource response of major geological events to organic matter enrichment in the study area and deepen the shale gas enrichment model.

The Junggar Basin is an important coal-bearing basin in northwestern China. The coalfield in the east of the Junggar basin is an important part of the large Xinjiang coal base, and contains rich coal resources. In this study, we undertook a multi-proxy study evaluating trace elements, macerals and vitrinite maximum reflectance from coal seams B0, B1 and B2 of the middle Jurassic Xishanyao Formation to characterize paleoredox and paleosalinity conditions of coal-forming swamp and atmospheric oxygen level and paleoclimate during coal-forming period in the eastern Junggar Basin. 220 coal samples were selected from coal seams B0, B1 and B2 in order to determine trace elements. Moreover, macerals and vitrinite maximum reflectance of 16 coal samples was investigated. Compared with average values for world low-rank coals, the coal seams B0, B1 and B2 of the middle Jurassic Xishanyao Formation in the eastern Junggar Basin are slightly enriched in Sr, in addition, the coal seam B0 is also slightly enriched in Co. The analysis of Ni/Co-V/Cr and Ni/Co-Mo diagrams indicates that swamp was in oxic and dysoxic condition, which infers that the water in swamp has strong activity and high free oxygen content. According to B/Ga ratio analysis, the paleosalinity of swamp gradually increases from coal seam B0 to coal seam B1 and then to coal seam B2. The high paleosalinity of swamp during coal-forming period of coal seam B2 may be caused by an increase in the evaporation of water, which also indicates that the paleoclimate was relatively dry and hot during this period. The Sr/Cu ratios in coal seams B0, B1 and B2 reveal that the paleoclimate experienced a gradual transition from relatively warm and humid condition to relatively dry and hot condition from bottom to top during the Xishanyao Formation coal-forming period. The inertinite content varies from 40.4% to 57.2% with an average of 48.5% in coal seams B0, B1, and B2. Inferred atmospheric oxygen concentration in the middle Jurassic, as estimated from inertinite contents, were ～27.7%, which is much higher than the minimum required for sustained combustion.

Abstract Forty Tertiary coals from Mukah-Balingian and Merit-Pila coalfields of the Sarawak Basin, Malaysia were investigated using bulk and molecular geochemical techniques such as proximate analysis, gas chromatography-mass spectrometry, elemental analyser, isotope ratio mass spectrometry, and inductively coupled plasma mass spectrometry to reconstruct their paleovegetation, paleoclimate, and environments of deposition. In addition, principal component analysis (PCA) of selected geochemical parameters was carried out to determine the controlling influences on the petroleum potential of the humic coals. δ13C values and the abundance of terpenoids imply the predominant contribution of angiosperms to the paleoflora. Bimetal proxies (Sr/Ba, Sr/Cu, and C-value), and δD values are generally suggestive of a warm and humid climate during the accumulation of the paleopeats. However, n-alkane proxies (P wax, P aq, n-C23/n-C29, etc.) and polycyclic aromatic hydrocarbons (PAHs) distribution suggest that Balingian coals accumulated under relatively drier and strongly seasonal paleoclimate in the Late Pliocene. When compared with published global average abundances, the investigated coals are mostly depleted in major oxides and trace elements, suggesting peat accumulation in freshwater-influenced environments. Nonetheless, higher (> 0.5 wt%) total sulfur content in some Mukah-Balingian coals suggests some degree of epigenetic marine influence. Furthermore, the low to moderately-high ash contents of the Sarawak Basin coals indicate the presence of ombrotrophic and rheotrophic peat deposits. PCA result of selected geochemical proxies suggests that source input, paleoflora, and marine incursions are not major controlling influences on the petroleum potential. However, climatic, and depositional conditions appear to slightly influence the petroleum potential of the studied humic coals.

The last deglaciation experienced the retreat of massive ice sheets and a transition from the cold Last Glacial Maximum to the warmer Holocene. Key simulation challenges for this period include the timing and extent of ice sheet decay and meltwater input into the oceans. Here, major uncertainties and forcing factors for the last deglaciation are evaluated. Two sets of transient simulations are performed based on the novel ice‐sheet reconstruction PaleoMist and the more established GLAC1D. The simulations reveal that the proximity of the Atlantic meridional overturning circulation (AMOC) to a bifurcation point, where it can switch between on‐ and off‐modes, is primarily determined by the interplay of greenhouse gas concentrations, orbital forcing and freshwater forcing. The PaleoMist simulation qualitatively replicates the Bølling‐Allerød (BA)/Younger Dryas (YD) sequence: a warming in Greenland and Antarctica during the BA, followed by a cooling northern North Atlantic and an Antarctic warming during the YD. Plain Language Summary: The last deglaciation, spanning roughly 20,000 to 10,000 years ago, marked a period of Earth's history characterized by the retreat of massive ice sheets that had covered large parts of the planet. During this phase, a drastic transition occurred from the cold Last Glacial Maximum to the warmer and more stable climate of the Holocene. A main challenge for simulating the last deglaciation is the timing and amplitude of the ice sheet decay and the amount of meltwater that enters into the oceans. Using two different reconstructions of ice sheets, we employ an efficient climate model to explore changes at the end of the last ice age. Our comparison shows notable differences in the timing and amplitude of abrupt climate events in the simulations using two different ice‐sheet reconstructions. Furthermore, we investigate the effects of factors such as greenhouse gases and Earth's orbital changes on the large‐scale ocean currents with respect to underlying ice sheets. Ultimately, our study sheds light on how different elements of the Earth's system shape the termination of the last ice age, enriching our understanding of Earth's climate history and guiding further deglaciation scenarios. Key Points: Transient simulations of the last deglaciation using GLAC1D and the new PaleoMist ice sheet reconstruction are compared for the first timeAMOC stability is impacted by ice sheet reconstruction used and the combination of forcings, indicating its proximity to a bifurcation pointPaleoMist simulation captures the BA/YD sequence signature in the northern North Atlantic [ABSTRACT FROM AUTHOR]

Global warming during the Last Glacial Termination was interrupted by millennial-scale cool intervals such as the Younger Dryas and the Antarctic Cold Reversal (ACR). Although these events are well characterized at high latitudes, their impacts at low latitudes are less well known. We present high-resolution temperature and hydroclimate records from the tropical Andes spanning the past ~16,800 y using organic geochemical proxies applied to a sediment core from Laguna Llaviucu, Ecuador. Our hydroclimate record aligns with records from the western Amazon and eastern and central Andes and indicates a dominant long-term influence of changing austral summer insolation on the intensity of the South American Summer Monsoon. Our temperature record indicates a ~4 °C warming during the glacial termination, stable temperatures in the early to mid-Holocene, and slight, gradual warming since ~6,000 y ago. Importantly, we observe a ~1.5 °C cold reversal coincident with the ACR. These data document a temperature change pattern during the deglaciation in the tropical Andes that resembles temperatures at high southern latitudes, which are thought to be controlled by radiative forcing from atmospheric greenhouse gases and changes in ocean heat transport by the Atlantic meridional overturning circulation. [ABSTRACT FROM AUTHOR]

The persistence and size of the Greenland Ice Sheet (GrIS) through the Pleistocene is uncertain. This is important because reconstructing changes in the GrIS determines its contribution to sea level rise during prior warm climate periods and informs future projections. To understand better the history of Greenland's ice, we analyzed glacial till collected in 1993 from below 3 km of ice at Summit, Greenland. The till contains plant fragments, wood, insect parts, fungi, and cosmogenic nuclides showing that the bed of the GrIS at Summit is a long-lived, stable land surface preserving a record of deposition, exposure, and interglacial ecosystems. Knowing that central Greenland was tundra-covered during the Pleistocene informs the understanding of Arctic biosphere response to deglaciation. [ABSTRACT FROM AUTHOR]

Aim: How the ability of plants to move towards newly favourable habitats (dispersal limitation) impacts the change of biome distribution and transition under fast climate warming is still debated. Analysing vegetation change in the past may help to clarify the relative importance of underlying ecological processes such as climate, biotic interactions, and dispersal. In this study, we investigated how dispersal limitation affected the distribution of European forests in the last 18,000 years. Location: Southern and Central Europe. Taxon: Spermatophyta. Methods: Using the LPJ‐GM 2.0 model (an extension of LPJ‐GUESS), we simulated European vegetation from the end of the Last Glacial Maximum (18.5 ka) to the current time (0 ka). Using biome reconstructions from pollen data as reference, we compared the performance of two dispersal modes: with no migration constraints or seed limitation (free dispersal mode), and with plant establishment depending on seed dynamics and dispersal (dispersal limitation mode). Results: The model run, including migration processes, was better at capturing the post‐glacial expansion of European temperate forests (and the longer persistence of boreal forests) than the setting assuming free dispersal, especially during periods of rapid warming. This suggests that a number of (temperate) tree taxa experienced delayed occupancy of climatically suitable habitats due to a limited dispersal capacity, i.e., post‐glacial migration lags. Main Conclusions: Our results show that including migration processes in model simulations allows for more realistic reconstructions of forest patterns under rapid climate change, with consequences for future projections of carbon sequestration and climate reconstructions with vegetation feedback, assisted migration and forest conservation. [ABSTRACT FROM AUTHOR]

Increased dust emissions from dryland areas and their effects on human health, ecosystem viability, and environmental change are a global concern in the face of the growing climate crisis. Dust plume emissions from the West African landmass, Sahara, and Sahel areas comprise a major fraction of the global aerosol budget. Dust plume intensity is closely related to regional winds (e.g., Harmattan, Sahara Air Layer), the Intertropical Convergence Zone, monsoonal seasonality, marine currents, and physiography. To study terrigenous material emitted from the continent over the last ~260 kyr (late Quaternary), we used X-ray fluorescence spectroscopy (XRF) to analyze a ~755 cm long marine sediment core from the eastern equatorial Atlantic Ocean, resulting in nearly 1400 discrete measurements. Spectral analysis results suggest that concentrations of elements (Rb, Sr, Si, Al) preserved in the sediments are correlated to different types of orbital climate forcing. Chemical weathering intensity indicated by the Rb/Sr ratio was sensitive to seasonal insolation variations controlled by precession cycles (23–18 kyr), which presumably reflects the relationship between monsoonal rainfall and sensible heating of the continent. Spectral analysis of silicate mineral grain size (Si/Al) showed significant 40 kyr cycles that were paced by obliquity. Based on these data, we infer that winter tradewind activity accelerated in response to the intertropical insolation gradient induced by high obliquity. High Rb/Sr ratios during the last glacial maximum and penultimate glacial maximum may have been due to a predominance of mechanical weathering over chemical weathering under dry/cool climates or the dissolution of Sr-bearing carbonates by corrosive glacial bottom waters. [ABSTRACT FROM AUTHOR]

The results of studying bottom sediments taken from the high-mountain lake Sagan-Nur located on the Oka plateau (East Sayan Mountains), which is insufficiently studied, are presented. The lake is freshwater and has a glacial origin. Comprehensive investigations of the mineral composition of the lake sediments accumulated over the past ~8600 cal. years have been carried out for the first time. The research methods include X-ray diffraction (XRD), infrared spectroscopy, laser granulometry, SiO2 bio determination, AMS, and 210Pb dating. The mineral composition of the bottom sediments is dominated by layered silicates, quartz, and plagioclase; furthermore, the X-ray amorphous component consisting of biogenic silica and organic matter is present. The method of mathematical modeling of their complex XRD patterns is used for correct identification of the layered silicates. It is established that the layered silicate assemblage is stable and is represented by muscovite, chlorite, illite, mixed-layer illite–smectite and chlorite–smectite, and kaolinite. At the same time, the structural characteristics and quantitative ratios of these minerals in the deposits changed significantly in response to changes in the natural environment of the region, which reveals the potential of a number of phyllosilicates (illite, mixed-layer minerals) as indicators of the paleoclimate in the bottom sediments of freshwater basins. The results of studying the sediment composition and, especially, the precision mineralogical–crystallochemical analysis of layered silicates have made it possible to reconstruct the paleolandscapes and climatic conditions of sediment accumulation and to assign them to the respective Holocene sub-stages. [ABSTRACT FROM AUTHOR]

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Stable isotope abundances (δ18O and δ2H) in regional aquifers can provide important paleoclimate information. However, identifying paleoclimate signals can be complicated by cross-formational mixing and, potentially, by isotopic diffusion between aquifers and confining units. We examine controls on δ18O and δ2H distributions in the Wilcox aquifer of the northern Gulf Coastal Plain (USA). We sampled groundwater for δ18O, δ2H, Cl−, and 36Cl along a ~300 km downgradient transect. We developed a simplified, 1D numerical model of groundwater flow and 18O transport to assess the possible importance of isotopic diffusion between the aquifer and its confining units. Along the inferred flowpath, δ18O and δ2H values were depleted by as much as 1.3 and 8.2‰, respectively, as the Wilcox aquifer transitioned from unconfined to confined. However, they then gradually rose farther downgradient by up to 1.1 and 8.6‰. Chlorine-36 analyses and 14C analyses (from other studies) indicate that groundwater ages range from ~103 yr to ~8 × 105 yr. Modeling results indicate that the effect of diffusion on isotopic abundances is limited, whereas Cl− data indicate that cross-formational flow is limited. Therefore, we posit that confined groundwater in our study reflects a Pleistocene paleorecharge signal. [ABSTRACT FROM AUTHOR]

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Copyright of Acta Sedimentologica Sinica is the property of Acta Sedimentologica Sinica Editorial Office and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

The regional impact of abrupt glacial climate variability remains poorly constrained for arid southwestern Asia, particularly winter dynamics during Marine Isotope Stage 3, due to limited paleoarchives in the Middle East. Here, we present continuous speleothem records of δ18O and δ13C with robust chronologies for southwestern and central Iran, spanning ∼50–30 ka. Stable‐isotope signals in the two stalagmites are generally uncorrelated and do not exhibit a consistent response to Greenland stadials or interstadials; however, both show a positive δ18O excursion that coincides with Heinrich event 4. We explore the potential mechanisms for intermittent coupling of speleothem δ18O across Iran through isotope‐enabled atmospheric modeling outputs, from which we utilize the spatial δ18O gradient as a proxy for wintertime westerly versus southerly jet strength. Our results suggest that during Heinrich event 4 and several Greenland stadials, stronger westerly winds enhanced Mediterranean moisture contributions to both sites and reduced aridity in southern Iran. Plain Language Summary: Stalagmites are useful archives to reconstruct the climate of the past. In order to shed light on the past climate of western Asia and the response of this region to the rapid climate changes, here we present two stalagmites from central and southwestern Iran that span 50,000 to 30,000 yrs ago. Our findings suggest that during extreme cold events, the moisture originates mostly from the west, whereas out of these extraordinarily cold periods moisture comes mostly from the south. Key Points: Continuous high‐resolution speleothem record of climatic change in southwestern and central Iran between 50 and 30 kaDecoupled responses of stable‐isotope gradients in central and southern Iran to glacial climate variability, except during Heinrich event 4Decreased impact of southerly moisture sources and reinforced westerlies during extreme cold events [ABSTRACT FROM AUTHOR]

Over recent decades, the southeastern United States (Southeast) has become increasingly well represented by the terrestrial climate proxy record. However, while the paleo proxy records capture the region's hydroclimatic history over the last several centuries, the understanding of near surface air temperature variability is confined to the comparatively shorter observational period (1895‐present). Here, we detail the application of blue intensity (BI) methods on a network of tree‐ring collections and examine their utility for producing robust paleotemperature estimates. Results indicate that maximum latewood BI (LWBI) chronologies exhibit positive and temporally stable correlations (r = 0.28–0.54, p < 0.01) with summer maximum temperatures. As such, we use a network of LWBI chronologies to reconstruct August‐September average maximum temperatures for the Southeast spanning the period 1760–2010 CE. Our work demonstrates the utility of applying novel dendrochronological techniques to improve the understanding of the multi‐centennial temperature history of the Southeast. Plain Language Summary: Tree‐ring data are important sources of paleoclimate information, which allow for the longer‐term evaluation of modern climate values and trends. Compared to much of North America, the Southeastern United States (Southeast) contains substantially fewer paleoclimate records from tree rings, and no estimates of past temperature variability which extend before the observational period. Employing a recently developed technique, which uses light reflectance properties of wood to obtain a representative metric of tree‐ring density, we develop a network of temperature‐sensitive tree‐ring records across the Southeast. These records enable us to reconstruct late summer maximum temperatures across the region spanning the period 1760–2023 CE. As few ground‐based, pre‐instrumental temperature records previously existed for this region, our reconstruction allows for an improved understanding of the region's multi‐centennial climatic history. Key Points: Maximum latewood blue intensity from tree rings can effectively be used to develop paleotemperature estimates for the southeastern USThe fidelity of tree‐ring density parameters for paleoclimate reconstruction are influenced by disturbance regimes and microsite conditionsCompared to the last 260 years, regional 20th‐century maximum late summer temperatures are not characterized by unprecedented positive trend [ABSTRACT FROM AUTHOR]

The impact of latitudinal variations in the Intertropical Convergence Zone (ITCZ) on northern Andean hydroclimate during the Medieval Climate Anomaly (MCA; 950–1,150 CE) and Little Ice Age (LIA; 1,300–1,850 CE) is uncertain. Synthesis of two new lacustrine paleoclimate records from the Eastern Colombian Andes with existing circum‐Andean records shows that effective moisture anomalies were synchronous and in phase across the tropical Andes during the last millennium. During the MCA, when the ITCZ was shifted northward, topographically controlled responses in the northern Andes to vigorous atmospheric convection resulted in low precipitation and high evaporation, while precipitation was also reduced in the southern tropical Andes. During the LIA, precipitation decreased in the northern Andes as the ITCZ migrated southward but was offset by cooling that lowered evaporation, establishing high effective moisture. In the southern tropical Andes, the southward ITCZ position simultaneously strengthened precipitation, increasing effective moisture. MCA‐like responses to continued warming trends could similarly reduce northern Andean precipitation while increasing evaporation, thereby lowering effective moisture and possibly reducing water resource availability. Plain Language Summary: The position of the tropical rain belt has been proposed as a leading control on Andean hydroclimate during the Medieval Climate Anomaly (MCA; 950–1,150 CE) and Little Ice Age (LIA; 1,300–1,850 CE), producing opposite hydroclimate conditions in the northern and southern tropical Andes. Using two new paleoclimate records from the eastern Colombian Andes and existing records from the northern and southern tropical Andes, we show that tropical Andean hydroclimate responses were similar, with generally warmer and drier conditions during the MCA and cooler and wetter conditions during the LIA. Whereas southern tropical Andean responses were in line with variations in the tropical rain belt, northern tropical Andean responses were not. For the northern Andes, we propose that slow‐moving, low‐energy convective precipitation during the MCA was blocked by the eastern Andes, resulting in reduced precipitation at elevation and in the interior Andes while warming increased evaporation. Wet conditions in the northern Andes during the LIA were the result of cool atmospheric temperatures that reduced evaporation and increased effective moisture despite low precipitation. This suggests topography and temperature played important roles in the northern Andean hydroclimate and that further warming could reduce effective moisture through topographic precipitation blocking and increased evaporation. Key Points: Tropical Andean hydroclimate variability was synchronous and in‐phase between the northern and southern hemispheres during the last millenniumOrographic influences on atmospheric convection‐controlled precipitation in the northern tropical Andes during the last millenniumMean annual temperatures controlled effective moisture in the northern tropical Andes vis‐à‐vis evaporation [ABSTRACT FROM AUTHOR]

The present work describes the taxonomic and paleobiogeographic study of two fossil woods related to extant Aspidosperma. The silicified specimens come from the fossil localities of Santa Ana (30°54′S, 57°55′W) and Concordia (31°19′S, 57°59′W), Entre Ríos Province, Argentina, belonging to the El Palmar Formation (Late Pleistocene). This unit represents the sedimentary body of the upper fluvial terrace generated by the Uruguay River in its middle basin in eastern Argentina. The anatomical features that distinguish the woods are growth rings delimited by axial parenchyma and fibers, semi-ring to-diffuse-porous woods; mainly solitary vessels; simple perforation plates; alternate, bordered, and vestured intervessel pits; scarce paratracheal and diffuse apotracheal axial parenchyma; homocellular, and uniseriate to-triseriate rays; non-septate fibers. Climate reconstruction modelled at the regional scale (Ecological Niche Modeling) revealed variations in macroecological diversity patterns of the nearest living relatives (Aspidosperma australe and A. polyneuron) over the last ca. 130,000 years. Optically stimulated luminescence dating of sediments from the upper part of the El Palmar Formation in the type area reveals that the unit spans from the Last Interglacial period (warm substage, MIS marine isotope stage 5a), to the penultimate interglacial (MIS 7). This period was characterized by warmer and wetter conditions than those observed today. The eco-anatomical characteristics of the fossil record reflect this type of environment. The modern analogues of the fossils studied here are now part of the forests that integrate the Atlantic forest and Araucaria forest biogeographic provinces in South America. [ABSTRACT FROM AUTHOR]

The present study investigates the response of west Pacific subtropical high (WPSH) to northern hemispheric warming due to natural and anthropogenic forcings. We carried out the analysis using a suite of climate model simulations for the mid-Holocene conditions based on the Paleoclimate Modeling Inter-comparison Project-3 (PMIP3) and quadrupled CO2 simulations based on the Climate Model Intercomparison Project-5 (CMIP5), representatives of natural and anthropogenic forcings. Both sets of simulations depict northern hemispheric warming and westward shift of WPSH during boreal summer. We found that the northern hemispheric warming increases the seasonal precipitation over Africa, central India and central-eastern Himalayas in the mid-Holocene and quadrupled CO2 climate, by causing northward shift of the ITCZ and enhanced moisture flux convergence. Enhanced condensational heating associated with precipitation increase over central India and eastern Himalaya, in both the climates, not only reinforces the South Asian High (SAH) in the upper-troposphere but also strengthens the WPSH and promotes its westward extension. Additionally, mid-tropospheric condensational heating over parts of northern Africa modulates the near-equatorial east–west circulation, induces anti-cyclonic circulation over equatorial Indian Ocean and Maritime continent and fosters westward extension of WPSH during boreal summer in both the climate. In short, precipitation changes induced by northern hemispheric warming modulates equatorial and subtropical east–west circulations and play a vital role in the longitudinal variations of WPSH under northern hemispheric warming climate. In a climate with strong northern hemispheric surface warming, we also noted a minimal role of warm pool SST in the westward extension of WPSH. [ABSTRACT FROM AUTHOR]

Fossil epifoliar fungi are valuable indicators of paleoenvironment and paleoecology. The Meliolaceae, members of which typically inhabit the surface of living plants as biotrophs or pathogens, is one of the largest groups of epifoliar fungi. In this study, we report a novel fossil species of Meliolinites Selkirk (fossil Meliolaceae), Meliolinites tengchongensis, on the lower epidermis of compressed fossil Rhodoleia (Hamamelidaceae) leaves from the Upper Pliocene Mangbang Formation of Tengchong, Yunnan, southwestern China. Meliolinites tengchongensis is characterized by web-like, superficial, brown to dark brown, septate, and branching mycelia bearing 2-celled appressoria and unicellular phialides. The fungal colonies also include ellipsoidal, 5-celled, 4-septate ascospores and dark brown perithecia with suborbicular outline and verrucose surface. The well-preserved vegetative and reproductive organs help us to explore the potential disease process of the new fossil species. Besides, the presence of fungal remains indicates that the fungal taxon might have maintained its host preference since at least the Late Pliocene. Furthermore, the occurrence of both fossil fungi and their host plants in Tengchong indicate a subtropical–tropical, warm, and humid climate during the Late Pliocene, whereas the distribution pattern of the fungi on the host leaves suggests that Rhodoleia may have been a part of the middle–upper canopies in the Tengchong Late Pliocene multilayered forest. [ABSTRACT FROM AUTHOR]

The stable carbon isotope composition of total organic matter (δ13Corg) has been utilized in aeolian sediments, serving as an indicator for reconstructing terrestrial paleoenvironments. The Qinghai Lake (QHL) Basin is a climate-sensitive region of significant importance in paleoclimatic reconstruction. However, the reconstructed climatic variations based on δ13Corg in aeolian sediments in the QHL Basin in the northeastern Qinghai-Tibet Plateau (QTP) are lacking, and their paleoclimatic significance remains poorly understood. By conducting δ13Corg measurements on the Niaodao (ND) aeolian profile near QHL, we reconstructed the paleoclimate changes of 11 ka–present. The variation range of the δ13Corg values in the ND profile indicated the terrestrial ecosystems were not the sole contributor to lacustrine organic matter. The δ13Corg values are an indicator of historical temperature changes in the study area, exhibiting similar trends with the reconstruction of Chinese summer temperatures, East Asian air temperature, global temperature, and Northern Hemisphere summer insolation at 37° N. The temperature increased with high frequency and amplitude oscillations, with strong aeolian activity and low total organic carbon accumulation during the Early Holocene. The temperature was maintained at a high and stable level, with the weakest aeolian activity and intensified pedogenesis during the Middle Holocene. The temperature decreased at a high rate, with renewed aeolian activity and weak pedogenesis during the Late Holocene. [ABSTRACT FROM AUTHOR]

A significant proportion of marine calcium carbonate sediments are comprised of metastable minerals that are susceptible to diagenetic alterations during burial. These reactions can reset the geochemical signature of sediments and pore fluids and influence elemental cycling in the ocean. However, the timing and mechanisms by which these reactions take place are poorly constrained. This study uses cores drilled on the slope of the Great Bahama Bank to provide quantitative constraints on important diagenetic reactions; namely respiration-driven dissolution, authigenic carbonate mineral formation, and conversion of aragonite to low Mg calcite (LMC). We perform detailed mineralogical characterization using newly acquired, high resolution X-ray diffraction (XRD) data and over 1000 reanalyzed XRD scans, characterize sediments texturally and elementally using electron microprobe data, calculate pore fluid saturation state with respect to aragonite using a Pitzer ion interaction approach, and use pore fluid chemistry and experimental distribution coefficients to predict authigenic carbonate compositions. These data suggest that aerobic organic matter oxidation, enabled by the advection of oxygenated seawater throughout the upper ∼ 30 m interval of sediment, causes undersaturation and thus dissolution of biogenic high Mg calcite (HMC) and aragonite. Deeper, anaerobic organic matter oxidation takes over and causes supersaturation, promoting authigenic precipitation in the form of HMC, which in turn decreases pore fluid Mg/Ca and promotes aragonite conversion to LMC. One novel aspect of this study is the identification of three types of calcites using the newly acquired XRD and electron microprobe data. Based on their unique crystallographic characteristics and chemical compositions, these types of calcites are interpreted to represent pelagic biogenic LMC, bank-derived biogenic HMC, and authigenic HMC precipitated from pore fluids. Notably, the composition of the authigenic calcite matches that predicted to precipitate from pore fluids using an empirical Mg partition coefficient in calcite. Calcites that form authigenically and from aragonite via replacement are suggested to recrystallize with burial as evidenced by the decrease in Mg content and micro-strain. This process-based geochemical framework assigns diagenetic processes to a specific depth window within the sediment column and paves the way for a mechanistic understanding of carbonate diagenesis, one that is rooted in thermodynamic and kinetic bases. [ABSTRACT FROM AUTHOR]

Wildfires significantly affect climate and environmental changes, closely tied to extreme weather responses. Vegetation combustion emits greenhouse gases (CO2, CH4, CO), warming the climate. Climate shifts, in turn, impact vegetation growth, altering combustible material types and quantities, thus affecting wildfire intensity, duration, and frequency. Wildfires profoundly affect ecosystems, influenced by factors like atmospheric oxygen and climate. Their combustion gases impact climate and vegetation growth. Recent advancements in studying ancient wildfires include analyzing nanoparticles as key indicators. This study discovered six types of nanoparticles in ancient wildfire remains, with sizes ranging from 50 nm to 500 nm and diverse compositions including elements such as C, O, Mg, Al, Ti, Fe, S, Ca, and P. These findings indicate that wildfires generate a variety of nanoparticles, offering new insights into ancient fire events. Elemental analysis revealed low magnesium but high calcium and aluminum levels, suggesting a warm, humid paleoclimate during these fires. The presence of high Ti-O ratios and carbon-rich nanoparticles points to ground fires with incomplete combustion. This research underscores the significance of nanoparticles in understanding the history and characteristics of ancient wildfires. [ABSTRACT FROM AUTHOR]