Paleoenvironmental Variations Research Articles

Morphological Diversity of Desmiophyllum Lesquereux Fossil Leaves and Related Palaeoenvironmental Implications from the Early Cretaceous of Northeastern Spain

A variety of leaves of different morphological sizes and venation types corresponding to the gymnosperm genus Desmiophyllum have been found in five fossil sites originating from the Barremian to the Cenomanian periods in northeastern Spain over an interval comprising 25 million years that encompasses the Early Cretaceous–Late Cretaceous boundary. These leaves are preserved in various lithologies corresponding to different depositional environments such as lagoonal systems, coastal swamps, deltaic plains, lacustrine environments and fluvial-related deposits. These new data shed light on the morphological and paleoenvironmental variability of Desmiophyllum recorded in the Cretaceous deposits from southwestern Eurasia.

Pleistocene to early Holocene paleoenvironmental evolution of the Abrolhos depression (Brazil) based on benthic foraminifera.

The paleoenvironmental evolution of the Abrolhos Depression (AD) on the southern Abrolhos Shelf during the global post-Last Glacial Maximum (LGM) transgression is investigated through benthic foraminifera analysis. Downcore sediment samples (core DA03A-5B) collected at a depth of 63m provide insights into the formation and paleoenvironmental variations of AD over the past 18 kyr BP. The core is divided into four biofacies based on foraminifera assemblages. At the base, the presence of carbonate concretions indicates a karstic surface, marking the initiation of the paleolagoon formation at approximately 13 kyr BP with low density of foraminifera, where species such as Elphidium sp. and Hanzawaia boueana (EH Biofacies) were more abundant. During the Younger Dryas (YD) (12.8-12.5 kyr BP), the AD exhibits two distinct phases: an initially confined lagoon environment with reduced circulation characterized by the dominance of the species Ammonia tepida (At Biofacies), followed by increased circulation characterized by higher density, richness, and diversity of benthic foraminifera. The end of the YD is identified by a significant biofacies change, indicative of a shallow marine environment, where the dominant species were A. tepida and Elphidium excavatum (AE Biofacies), supported by sedimentological and geochemical proxies. This paleoenvironmental shift is associated with Meltwater Pulse (MWP) -1B, suggesting a connection to a shallow marine environment. As sea levels continue to rise, the AD transitions into an open marine setting. However, around 8 kyr BP, a change occurs with the absence of A. tepida and the occurrence of planktonic and other benthic foraminifera typical of the outer shelf, indicating depths greater than 50m (HQ Biofacies). The findings highlight the complex interplay between climate fluctuations, sea-level changes, and the formation of coastal environments during the LGM transgression. This study contributes to our understanding of paleoenvironmental dynamics, adding valuable insights to the evolutionary history of AD. The results emphasize the importance of integrating benthic foraminifera analysis, radiocarbon dating, and geochemical proxies to reconstruct paleoenvironments accurately. Overall, this research enhances our knowledge of global continental shelf evolution during the post-LGM transgression and provides valuable information for future paleoenvironmental studies.

Climate variability in northern Africa during the late Holocene: A multiproxy perspective from El-Beida Lake (Wadi El-Natrun, Egypt)

North Africa is a key region hosting ca. 230 million people that are dependent on climate to maintain their subsistence through agriculture. Because of the current global changes, understanding the mechanisms behind the climate variations that occurred in this region is extremely important. To contribute to a more accurate modelling projection, we reconstructed the paleoclimatic and paleoenvironmental variations from the Meghalayan (∼1,500 ka) to recent using palynological and geochemical data from a sediment core from El-Beida Lake (Wadi El-Natrun area, north Western Desert of Egypt). North Africa underwent significant shifts in climatic conditions forced by different drivers since the Roman Warm Period (RWP) until recent. Our sediment core record indicates that this region experienced a persistent dry and warm climate during the RWP until the first half of the Medieval Climate Anomaly (MCA). The positive North Atlantic Oscillation was the main driver for controlling the precipitation pattern and pushing the precipitation towards central and north Europe and favoring the dry climate in North Africa during the RWP. The dry and slightly cold conditions in the study area during the Dark Age Cold Period (DACP) can be ascribed to the coupling between the more southward position of the Azores Front and the weak Atlantic Meridional Overturning Circulation. Northern Africa showed variable climatic conditions during the Medieval Climate Anomaly (MCA) due to the complicated thermohaline circulation of the Mediterranean Sea. During this time, the Eastern Mediterranean experienced a cold or partially cold MCA that may be extended to the present study area. An abrupt change to humid and cold climatic conditions occurred in northern Africa during the Little Ice Age (LIA) due to large-scale processes like the ENSO and NAO. The SST warming of the North Tropical Atlantic (NTA), significantly influenced by ENSO, causes the position of the Atlantic ITCZ to be shifted northward affecting precipitation in Africa.

Middle and Late Holocene paleolimnological changes in central Lake Tanganyika: Integrated evidence from the Kavala Island Ridge (Tanzania)

Middle and Late Holocene sediments have not been extensively sampled in Lake Tanganyika, and much remains unknown about the response of the Rift Valley’s largest lake to major environmental shifts during the Holocene, including the termination of the African Humid Period (AHP). Here, we present an integrated study (sedimentology, mineralogy, and geochemistry) of a radiocarbon-dated sediment core from the Kavala Island Ridge (KIR) that reveals paleoenvironmental variability in Lake Tanganyika since the Middle Holocene with decadal to centennial resolution. Massive blue-gray sandy silts represent sediments deposited during the terminal AHP (~5880–4640 cal yr BP), with detrital particle size, carbon concentrations, light stable isotopes, and mineralogy suggesting an influx of river-borne soil organic matter and weathered clay minerals to the lake at that time. Enhanced by the AHP’s warm and wet conditions, chemical weathering and erosion of Lake Tanganyika’s watershed appears to have promoted considerable nutrient recharge to the lake system. Following a relatively gradual termination of the AHP over the period from ~4640 cal yr BP to ~3680 cal yr BP, laminated and organic carbon-rich sediments began accumulating on the KIR. δ15Nbulk, C/N, and hydrogen index data suggest high relative primary production from a mix of algae and cyanobacteria, most likely in response to nutrient availability in the water column under a cooler and seasonally dry climate from ~3680 to 1100 cal yr BP. Sediments deposited during the Common Era show considerable variability in magnetic susceptibility, total organic carbon content, carbon isotopes, and C/N, consistent with dynamic hydroclimate conditions that affected the depositional patterns, including substantial changes around the Medieval Climate Anomaly and Little Ice Age. Data from this study highlight the importance of sedimentary records to constrain boundary conditions in hydroclimate and nutrient flux that can inform long-term ecosystem response in Lake Tanganyika.

Hydroclimate and Paleoenvironmental Variability from the Tonle Sap Lake Basin during the Angkor Period

Hydroclimate and Paleoenvironmental Variability from the Tonle Sap Lake Basin during the Angkor Period

Nitrogen isotopes of marine oils in the Tarim Basin, China: Implications for the origin of organic matters and the paleoenvironment

Nitrogen isotope compositions (δ15N) of sedimentary rocks are usually used to reconstruct the paleoenvironment and nitrogen (N) biogeochemical cycle. The δ15N values of crude oils inherit the characteristics of relevant source rocks and can well reflect the information of hydrocarbon-forming organisms and environment in ancient water column. However, studies on the δ15N of crude oils are limited due to the low N content. In this study, a new efficient method is applied to the marine oils from the Bashituo (BST) and Halahatang (HLHT) areas of the Tarim Basin to obtain the nitrogenous components (i.e., nonhydrocarbons and asphaltenes) for the achievement of N concentration. The carbon and nitrogen isotopes of these components and the biomarkers of oils were measured. The δ15N values in asphaltenes (δ15NAsp) are significantly heavier than those in nonhydrocarbons (δ15NNSOs) in these oils, which are attributed to the potential directional N transfer and kinetic isotope fractionation during the thermal evolution of organic matters (OM). The δ15NAsp values have significant correlations with OM origin associated parameters and weak correlations with environmental parameters, suggesting that the difference in δ15NAsp values is mainly resulted from biological source rather than redox conditions. The δ15NNSOs values have a closer relationship with the redox condition than biological characteristics, indicating that they have a good response to paleoenvironmental variation in the water column, which is not completely overprinted by the difference of OM origin. Different redox conditions give rise to distinct nitrogen cycles, resulting in various δ15N values. Anammox occurs in the water column of the Early Cambrian dominated by physically stratified conditions with significant isotope fractionation, resulting in relatively heavier δ15N of OM in the BST area. In the Middle–Late Ordovician period, the limited suboxic zone leads to an insignificant positive bias of δ15N caused by partial denitrification in the HLHT oils. The evaluation of δ15N in nitrogenous fractions enables a more comprehensive reconstruction of N cycle for ancient oceans.

Sedimentary provenance and paleoenvironmental evolution since the Last Glacial Maximum off the Xisha Platform, northern South China Sea

The complexity of retrieving paleoenvironmental variability from hemipelagic sedimentary archives in the marginal seas has been exacerbated by intricate interactions between sedimentary sources and climatic fluctuations, modulated by sea-level shifts and oceanic currents. These challenges are particularly pronounced in the northern South China Sea (SCS). This study introduces new data, incorporating SrNd isotopic, clay minerals, grain-size, and calcareous nannofossil proxies, to assess the sedimentary provenance and paleoenvironmental changes in the northwestern SCS since the Last Glacial Maximum. The sedimentary provenance highlights the primary source from the northern SCS, particularly the Red River drainage system, with potential contributions from the Indochina drainage systems. The combined analysis of multiple proxies suggests that sedimentary processes and biotic activity in the examined core were mainly influenced by sea-level fluctuations, concerning global ice dynamics. Variations of grain sizes and kaolinite / (illite + chlorite) (K/(I + C)) ratio largely correspond to the terrestrial flux variation from northern SCS associated with sea-level changes during glacial-interglacial cycles. Furthermore, the smectite / (illite + chlorite) (S/(I + C)) ratio in this study appears to have been primarily influenced by the activity of the Kuroshio current in the northern SCS. The possible interference of intensified northeastward warm currents during relatively warm intervals caused the depletion of the S/(I +C) ratio and was responsible for the depletion of soluble calcareous nannofossils. Additionally, this study deduces that sedimentary processes and biotic activity in the northern SCS, in response to mainly sea-level changes and surface currents, were largely controlled by global ice dynamics and solar radiation. This study also underscores the need for further interdisciplinary research, combining various proxies, to enhance our understanding of paleoenvironmental assessments in hemipelagic sediments in marginal seas.

The Incomplete Record of Autogenic Processes Sets Limits on Signal Detectability

AbstractSpectral analysis is a central tool regularly used by the scientific community to identify the presence of periodic processes within a time series of information, as spectral peaks at an imposed periodicity can be differentiated from internal (autogenic) variance. In scientific disciplines, such as seismology, the time series of information is of high temporal resolution. Hence, although temporal gaps are present, they do not impact the overall noise structure, meaning that the full spectrum of autogenic variance can be reconstructed. However, power spectra generated from stratigraphic information are affected by temporal incompleteness due to varying episodes of erosion and geomorphic stasis, which generate gaps over a range of scales. This removes information related to the natural and autogenic variability present within sediment‐transport systems, which makes it challenging to accurately reconstruct the structure and strength of paleo‐surface processes, which defines the detectability of past environmental signals. We explore how incompleteness impacts the temporal structure of autogenic noise within power spectra, and how this influences the detectability of spectral spikes related to environmental signals. We utilize a sediment flux time series from a physical rice pile and progressively degrade these data to mimic varying degrees of stratigraphic incompleteness. We find that incompleteness strongly influences the timescales and spectral structure of autogenic noise evident, and can render signals over all periodicities undetectable within a highly incomplete time series. This offers the ability to confidently justify the interpretation of subtle environmental signals from field measurements and understand the records that may best preserve paleoenvironmental variability.

Paleoenvironmental variations during the Late Cambrian: Implications from Zn isotopes, I/(Ca+Mg) ratios, and other elemental proxies

The Upper Cambrian at the Martin Point section (∼110 m-thick) in western Newfoundland is a part of the Cow Head Group and partially spans the coeval Tuckers Cove and the Martin Point members of the Shallow Bay and Green Point formations, respectively. These units comprise alternating shale, minor conglomerate beds, and limestone rhythmites of a toe-of-slope apron. Earlier studies of the C-isotope profile, based on the lime mudstone interbeds, documented global negative δ13Ccarb shifts (from old to young: NL1, NL2, HERB) correlated with the lowermost Proconodontus posterocostatus, Proconodontus muelleri and base of Eoconodontus notchpeakensis conodont zones, respectively (post-Steptoean Positive Carbon Isotope Excursion NL1 and NL2 and Hellnmaria-Red Tops Boundary-HERB). Samples were extracted from the most preserved spots of micritic to near-micritic grain size (≤4 μm−10 μm). Fabric retention confirms petrographic preservation and insignificant correlations (R2 ≤ 0.1) of diagenetic proxies (e.g., Sr) with their environmental counterparts support the preservation of at least near-primary geochemical signatures. The paleoenvironmental proxies (TOC, Zn, P, Cu, Al/Ti, Mn, Fe, V, Mo) support dominant dysoxic conditions. The δ66Zn values (0.09–0.73 ‰ JMC Lyon) and (I/(Ca + Mg)) ratios (0.02–0.48 μmol/mol) vary consistently throughout the studied events. The minor decreases in δ66Zn values seem to denote inhibition of bioproductivity in a dysoxic water column, consistent with warm and humid climate during general transgressive settings and shoaling of organic-rich water into the shallow environment. The low I/(Ca + Mg) ratios (<0.5 μmol/mol) reinforce this interpretation, suggesting general dysoxic settings throughout the entire section.

Paleoenvironmental variations indicated by microfossils in the upper paleozoic Konservat-Lagerstätte of the Paraná Basin, Santa Catarina, Brazil

The Lontras Shale is a Brazilian Paleozoic Konservat-Lagerstätte that preserves a remarkable diversity of fossils in an exceptional way. In this study, we aimed to refine the paleoenvironment of the Lontras Shale, in the city of Mafra at Santa Catarina State, using microfossils and phytoclasts as proxies. Sampling was conducted in twelve layers of the shale (1A, 1B, 1C, 1D, 2A, 2B, 3A, 3B, 3C, 3D, 4A, 4B) in a 1.2m outcrop. The samples were collected every 10 cm and weighed 1 kg each. The collected material underwent chemical treatment with 15% hydrogen peroxide for 24 h. Samples were then washed and dried, and all the total fractions were observed under a stereomicroscope. A total of 316 bioclasts (entire fossils or fragments) were identified. Thirty-three of the specimens were analyzed in a scanning electron microscope. As a result, we identified Foraminifera classified as Saccammina sp., Psammosphaera irregularis and Ammobaculitessp. The preservation level of the phytoclasts suggests that these fragments were deposited under a proximal environment. The analysis of the microfossils suggests that the Lontras Shale Konservat-Lagerstätte in the city of Mafra experienced significant changes in its paleoenvironment settings during deposition. The high concentration on the layer 3D suggests an increase in the nutrient supply or temperature variation during the Lontras Shale deposition. Finally, the data provided through microfossil analyses combined with preterit information could support that the Lontras Shale Konservat-Lagerstätte was deposited under a proximal environment such as an estuary or a fjord.

The build-up of the present-day tropical diversity of tetrapods

The extraordinary number of species in the tropics when compared to the extra-tropics is probably the most prominent and consistent pattern in biogeography, suggesting that overarching processes regulate this diversity gradient. A major challenge to characterizing which processes are at play relies on quantifying how the frequency and determinants of tropical and extra-tropical speciation, extinction, and dispersal events shaped evolutionary radiations. We address this question by developing and applying spatiotemporal phylogenetic and paleontological models of diversification for tetrapod species incorporating paleoenvironmental variation. Our phylogenetic model results show that area, energy, or species richness did not uniformly affect speciation rates across tetrapods and dispute expectations of a latitudinal gradient in speciation rates. Instead, both neontological and fossil evidence coincide in underscoring the role of extra-tropical extinctions and the outflow of tropical species in shaping biodiversity. These diversification dynamics accurately predict present-day levels of species richness across latitudes and uncover temporal idiosyncrasies but spatial generality across the major tetrapod radiations.

Late Barremian–Aptian paleoenvironmental variations and OAE1a environmental effect in the eastern Crimea

The early Aptian Oceanic Anoxic Event 1a (OAE1a, or Selli Event) is widely known from many oceanic and inland sections as an interval of enhanced accumulation of sediments rich in total organic carbon (TOC), associated with the turnover in the global carbon budget and dramatic biotic variations. Our multidisciplinary study of the upper Barremian to lower upper Aptian deposits from the eastern part of Crimean Peninsula allowed us to confirm the presence of a layer that correlates to OAE1a and revealed significant reorganization in the planktonic and benthic foraminifera, nannofossils, ostracod and terrestrial plant communities at this level. The low-calcareous OAE1a deposits from the eastern Crimea lack in TOC that is not typical sedimentological response to this critical event. The OAE1a onset was associated with a nannoconid crisis, occurrence of low-abundance Hedbergella planktonic foraminifera, increased abundance of benthic foraminifera and ostracods and the bloom of Classopolis on the adjacent land. The calcareous microplankton biota was highly oppressed during OAE1a up to total elimination in the core of the event. Benthic assemblages indicate the occurrence of dysoxic conditions at the sea-floor. The absence of organic matter in the deposits of the OAE1a interval points to the low basinal biotic productivity and low input of terrestrial organic matter. We suggest that oligotrophication of the basin was related to the transgressive pulse, which led to small-scale landward moving of the coastal line barriered by coastal highland. The hot arid climatic conditions indicated by terrestrial plants, prevented the supply of nutrients and terrestrial organic matter into the basin that caused low algal and bacterial productivity and prevented accumulation of TOC-rich sediments. The termination of OAE1a coincides with the occurrence of warm humid climate and erosion of ephemeral coastal highland, more likely, built up by soft clayey sediments. The transit restoration of the normal marine biota in the early late Aptian was interrupted in the middle late Aptian by new long-lived regression led to enhanced terrestrial runoff and, possibly, fresh water input killed marine biota and caused the accumulation of low-calcareous clay.

Modeling the decomposition signal and correcting bulk organic data from a peat deposit, a case study at low latitudes (Cameroon)

Organic compounds are widely used for paleoclimatic and paleoenvironmental reconstructions. Bulk organic proxies, however, are more complicated to interpret due to the multiple causes of variation in climatic and environmental conditions and the degree of diagenetic alteration. As labile compounds, rich in easily degradable function and generally richer in heteroatoms such as oxygen and nitrogen, decompose, the remaining organic matter becomes progressively richer in refractory carbon and its carbon content increases. Thus, in a peat deposit composed almost entirely of organic matter, total organic carbon (TOC) is expected to increase with time and depth, which could mask the paleoclimatic signal. We propose a simple model for peat sediments to remove the decomposition signal based on a logarithmic function fitted with a partial dataset where decomposition is the main parameter. The subtraction of the obtained logarithmic function to the raw data (i.e., measured data) leads to “residual” data. We discuss the influence of different parameters (water table depth, vegetation, microbial community) on the “residual” data and their possible link to paleoclimatic and paleoenvironmental variations. This method is tested on bulk elemental and isotopic data obtained from a new peat core from the Adamawa Plateau (North-East Cameroon) covering nearly 10 ka cal BP. Comparison with Rock-Eval® parameters highlights similar variations between the Hydrogen Index and residual TOC variations, supporting the interpretation based on residual TOC. Our approach allows to extract paleoenvironmental information from decomposition-prone bulk organic proxies and can be generalized to peat deposits where decomposition plays a major role in controlling bulk data.

A NEW RECORD OF PALEOENVIRONMENTAL CONDITIONS FROM THE NORTHEASTERN SAN MARTÍN LAKE BASIN (PATAGONIA, ARGENTINA): VEGETATION RECONSTRUCTION FROM POLLEN AND CARBON ISOTOPES SINCE 10,200 CAL. YEARS BP

In this research, we reconstruct the paleoenvironmental conditions from a sedimentary record of a wetland (mallín) located in the Patagonian steppe near to the Subantarctic forest on the northeastern shore of the San Martín Lake basin (SW Santa Cruz, Patagonia, Argentina). The Mallín Ñire (49° 00’ 23.5” S; 72° 13’ 34.5” W) presents a basal age of 10,200 cal. years BP and its pollen content, carbon isotopes, and stratigraphy were analyzed. The relationship with modern pollen assemblages from surface sediment samples allows us to interpret changes in the fossil record. Between 10,200 and 9,000 cal. years BP, we can infer a grass-shrub steppe with dwarf-shrubs under arid conditions and between 9,000 and 6,500 cal. years BP, a grass steppe dominated under an increase of moisture availability. Conditions became drier until 4,000 cal. years BP; later, a grass-shrub steppe developed, which suggests an environmental transition like the modern ones. The last 1,400 cal. years BP present high paleoenvironmental variability. The integration with other sequences allowed us to interpret the regional changes during the Holocene related to moisture availability by precipitation changes related to the westerly variations.

Mechanism of organic matter accumulation in black shale of the Datangpo Formation: Insights from paleo-environmental variation during the Cryogenian non-glaciation

Mechanism of organic matter (OM) accumulation in the Cryogenian Datangpo Formation of the Nanhua Basin is poorly understood, restricting shale-gas exploration in these non-glacial deposits. To understand mechanism of OM accumulation, we carried out high-resolution analyses of geological and geochemical data from shales of the lower three members (I.II.III) of the Datangpo Formation across the basin. The results show that OM distribution in the basin is heterogeneous: (1) stratigraphically, total organic carbon (TOC) concentrations vary from moderate values in Member I, peaks in Member II, to lowest values in Member III; and (2) spatially, TOC concentrations in Member I increase with increasing depositional water depths, whereas they are high and low throughout Member II and Member III across the basin, respectively. The heterogeneity of OM accumulation in shales is interpreted to be controlled by complex paleo-environmental variations in water-mass exchange, paleoclimate, seawater redox state, and hydrothermal activities. Specifically, (1) ferruginous-euxinic conditions, intensive hydrothermal activities, and pronounced water-mass exchange between the basin and the open ocean favored OM accumulation in Member I; (2) expanded euxinic conditions, dramatic chemical weathering, and reduced water-mass exchange resulted in OM enrichment in Member II; and (3) less extensive anoxic conditions, reduced chemical weathering, and stagnant water-mass exchange led to OM depletion in Member III. This integrated conceptual model for OM accumulation in shales of the Datangpo Formation shows the influences of both primary productivity and redox conditions in the Nanhua Basin.

Environmental forcing by submarine canyons: Evidence between two closely situated cold-water coral mounds (Porcupine Bank Canyon and Western Porcupine Bank, NE Atlantic)

Within the Porcupine Bank Canyon (NE Atlantic), cold-water coral (CWC) mounds are mostly found clustered along the canyon lip, with individual disconnected mounds occurring nearby on the western Porcupine Bank. Remotely operated vehicle-mounted vibrocoring was utilized to acquire cores from both of these sites. This study is the first to employ this novel method when aiming to precisely sample two closely situated areas. Radiometric ages constrain the records from the early to mid-Holocene (9.1 to 5.6 ka BP). The cores were then subjected to 3D segmented computer tomography to capture mound formation stages. The cores were then further examined using stable isotopes and benthic foraminiferal assemblages, to constrain the paleoenvironmental variation that influenced CWC mound formation of each site. In total, mound aggradation rate in the Porcupine Bank Canyon and western Porcupine Bank was comparable to other Holocene CWC mounds situated off western Ireland. Results derived from multiproxy analysis, show that regional climatic shifts define the environmental conditions that allow positive coral mound formation. In addition, the aggradation rate of coral mounds is higher adjacent to the Porcupine Bank Canyon than on the western Porcupine Bank. Benthic foraminifera assemblages and planktic foraminiferal δ13C reveal that higher quality organic matter is more readily available closer to the canyon lip. As such, we hypothesize that coral mound formation in the region is likely controlled by an interplay between enhanced shelf currents and the existence of the Eastern North Atlantic Water-Mediterranean Outflow Water-Transition Zone. The geomorphology of the canyon promotes upwelling of these water masses that are enriched in particles, including food and sediment supply. The higher availability of these particles support the development and succession of ecological hotspots along the canyon lip and adjacent areas of the seafloor. These observations provide a glimpse into the role that submarine canyons play in influencing macro and micro benthic fauna distributions and highlights the importance of their conservation.

Interpretation of abnormally negative carbon isotope excursions in Eifelian–Givetian (Middle Devonian) sediments of South China and implications for paleo-environmental variation

Many negative carbon isotope excursions (NCIEs) have been employed to interpret global biogeochemical events in Earth history, but they are also influenced by local depositional settings and diagenetic alteration, thus making it difficult to link them to global events. Like the NCIEs in Middle Devonian sediments of North America, similar NCIEs were also observed in the age-equivalent sediments of South China, and therefore it is necessary to further address the logical significance of these intercontinentally comparable NCIEs. Here, we present major and trace elements as well as δ15N, δ13Ccarb, and δ13Corg records across the Middle Devonian Eifelian–Givetian transition in the intra-platform basin of South China. The changes in stable isotopes (δ13Ccarb, δ13Corg, δ18Ocarb, and δ15N) and their relationships may jointly indicate limited influence of diagenetic processes. Our abnormally negative δ13Ccarb values (−7 to −5‰), even lighter than the mantle input end-member value (∼ −5‰), cannot be easily explained by dramatic changes in the δ13C values of global dissolved inorganic carbon (DIC) reservoir. In a restricted platform basin, enhanced nutrient input may stimulate high paleo-productivity, resulting in the depletion of DIC concentrations in surface waters. CO2 is then replenished via invasion from the atmosphere, and intense evaporative conditions may promote the large isotopic fractionation of CO2 invasion owing to hydration reactions of aqueous CO2. Our NCIEs are most likely related to the local 13C-depleted values of platform DIC owing to CO2 invasion associated with large isotopic fractionation due to enhanced evaporation and primary productivity. The “productivity-anoxia feedback” mechanism can explain the coupled changes in our terrestrial clastics input, productivity, and redox proxies. By combining redox proxies and C and N isotopic records, we further propose a model for local carbon and nitrogen cycling in a restricted and evaporative intra-platform basin. Our study highlights local depositional controls on NCIEs, and these local factors should be considered before NCIEs are applied to understand the global carbon cycle perturbations during the Middle Devonian.

How Can Phenotypic Evolution be Characterized Over Time and Through Environmental Changes?

Rapid phenotypic evolution is observed in response to rapid environmental changes. These phenotypic variations can occur at different scales, from the population to the community. We intended to characterize these multiscale phenotypic responses in rodents from the archaeological site El Harhoura 2 (Rabat, Morocco), dated from the Late Pleistocene to the Holocene, and relate them to paleoenvironmental variations. Upper and lower first molars were used as proxies for phenotype. Their shape was quantified using a landmark-free method. To account for both intra- and interspecific variations, we used morpho-groups as phenotypic units. Those morpho-groups were identified using unsupervised clustering. Three shape indicators were computed: number of morpho-groups, morpho-group disparity and changes in morpho-group mean shape over time. To evaluate this little-used approach on small mammals, we compared it to three widely used biodiversity indices: number of taxa, Shannon index, and Simpson index. Phenotypic evolution between and within species was highlighted. Morpho-groups seemed to be phenotypic response units representing ecological groups that transversed species. Variations in the morpho-group mean shapes were partly related to paleoenvironmental changes; however, variations in disparity were not. Thus, environmental changes deduced from fossil microvertebrate communities did not seem to be the main determinants of the characterized phenotypic variations.

Variations by degrees: Western European paleoenvironmental fluctuations across MIS 13–11

Marine Isotope Stages (MIS) 13–11 saw a major transformation in the hominin occupation of Europe, with an expansion in the scale and geographical distribution of sites and artifact assemblages. That expansion is explored here in the context of paleoenvironmental variability, focusing on geographical and chronological trends in climatic and habitat conditions at and between key Lower Paleolithic sites in Western Europe. Climatic conditions at British sites are compared across MIS 13–11, and used to test predicted values from the Oscillayers data set. Conditions at hominin and nonhominin sites are compared to explore possible limitations in hominin tolerances during MIS 13–11. Trends in conditions are explored with reference to long-term global patterns, short-term substage events, and seasonal variations. The apparent increase in the scale of hominin activity in north-western Europe during MIS 13 is surprising in light of the relatively harsh conditions of late MIS 13, and is likely to reflect significant physiological and/or behavioral adaptations, a mild south-north temperature gradient in western Europe during MIS 13, and the relatively mild, sustained conditions spanning MIS 15–13. The expanded occupation of north-western Europe during MIS 11 probably reflects the extended mild conditions of MIS 11c, since marked seasonal temperature differences and substantial behavioral changes between hominin sites in MIS 13 and 11 are not clearly evident. Site-specific conditions in south-western Europe during MIS 11 suggest milder winters, warmer summers, and reduced seasonal variability compared to north-western Europe. Some or all of these conditions may have supported larger, core populations, as may the relatively mild conditions associated with south-western European sites during MIS 12. Finally, comparisons between north-western and north-central European sites indicate relatively small differences in seasonal temperatures, suggesting that climate may only be a partial factor behind the smaller-scale occupations of north-central Europe during MIS 13–11.

Environmental reconstruction potentials of Loess-Paleosol-Sequences in Kashmir through high-resolution proxy data

Loess Paleosol Sequences (LPS) are valuable archives of climatic and environmental change in terrestrial systems and contribute to local and global dust systems. Due to their widespread occurrence across continents, LPS are well suited to study the interface of climate subsystems, on different time scales. Yet, high-resolution investigations of LPS have been mainly performed in Europe, East Asia and North America. In contrast, other loess-covered areas are less intensively studied, and low sampling resolution often limits the assessment of the full potential of these paleo-environmental archives. This is particularly true for LPS in the Kashmir region, where competing monsoonal- and continental climate subsystems in Southern Asia interact. In this study, we test the potential of the Wanihama LPS in the northern fringe of the Kashmir Valley to reflect climatic- and paleo-environmental variability between- and within stratigraphic units. For this, we present the stratigraphic log of the section and contribute a high-resolution (2 cm interval) dataset comprising rock-magnetic parameters, grain size- and colorimetric data for the Wanihama LPS in Kashmir. Overall, our multi-proxy-study supports the stratigraphy to different degrees. Classic climate-driven magnetic enhancement in paleosols is evident, despite possible waterlogging effects through monsoonal influences. Our results highlight the potential of LPS in Kashmir and illustrate the need for reliably dated logs with proxy data in a high resolution, to i) validate the LPS in the context of paleo-environmental and climatic studies, and to ii) establish a correlative framework for LPS across Kashmir and beyond. Once high-resolution proxy data are available for long and continuous LPS in Kashmir, we will be able to gain a better understanding of interactions between climate sub-systems in the context of oscillating supra-regional climate systems in Southern Asia.