Multi-proxy Study Research Articles

Carbon Isotopic Signature and Organic Matter Composition of Cenomanian High-Latitude Paleosols of Southern Patagonia

The Cenomanian Mata Amarilla Formation (MAF) in southern Patagonia (~55° S paleolatitude, Austral-Magallanes Basin, Argentina) is composed mainly of stacked fluvial deposits with intercalated paleosols, which document Cenomanian environments at high-paleolatitudes in the Southern Hemisphere. We performed a multiproxy study of the paleosols and sediments of the MAF in order to (1) understand the composition of the soil- and sediment-derived organic matter (OM), (2) apply carbon isotope stratigraphy as a tool to correlate patterns obtained from the MAF with existing marine and non-marine δ13Corg records worldwide, and (3) investigate the relationship between variations in spore-pollen assemblages of the MAF and the climatic conditions prevailing in the Cenomanian Southern Hemisphere. An integrated dataset was generated, including total organic carbon content, Rock-Eval pyrolysis data, stable isotope (δ13Corg) composition, and palynological data, combined with published paleosol-derived mean annual temperatures and mean annual precipitations. The results indicated that the OM preserved in the MAF paleosols allowed its use as a chemostratigraphic tool. The MAF δ13Corg curve showed the rather stable pattern characteristic for the Early to Late Cenomanian interval. The absence of the major positive carbon isotope excursion associated with oceanic anoxic event 2 provided an upper limit for the stratigraphic range of the MAF. The palynological data suggested the development of fern prairies during warmer and moister periods at the expense of the background gymnosperm-dominated forests. Overall, the multiproxy record provided new insights into the long-term environmental conditions during the Cenomanian in the high latitudes of the Southern Hemisphere.

Late Holocene Hyrcanian forest and environmental dynamics in the mid-elevated highland of the Alborz Mountains, northern Iran

We present a high-resolution multi-proxy study including pollen, spores, non-pollen palynomorphs, charcoal, loss on ignition, and geochemical analysis from the radiocarbon dated sediment core of Annal Lake. The lake is located at 700 m elevation in the Hyrcanian forest of the Gilan province, northern Iran. Between ca. 1690 and 1450 cal yr BP, a mixed forest with Alnus, Carpinus, Quercus, and Fagus were present, as well as patches of grassland areas around the lake. At ca. 1450 cal yr BP, the forest expanded and reduced the open grassland areas until 65 cal yr BP. Different proxies indicate that humans were present in the studied area since the beginning of the recorded period. However, since 65 cal yr BP, human impact increased markedly by deforestation and cattle grazing, and settlers probably changed from pastoralism to more farmers. Ratios of geochemical elements such as V/Cr, K/Al, Rb/Al, Si/Fe, and Ca/K suggested the warmest period with the higher amount of rainfall and detrital inputs forming a shallow lake between ca. 1690 and 580 cal yr BP. In contrast, a colder and drier period occurred between ca. 580 and 250 cal yr BP, mostly corresponding to the Little Ice Age period. Based on the geochemical element ratios, the highest detrital inputs (Ti), the highest lake level (V/Cr, Rb/Al, K/Al), and the wettest climatic conditions (Ca/Ti) with high rainfall and a relatively stable climatic conditions occurred for the last ca. 250 cal yr BP since the recorded period.

APPLICATION OF 14C METHOD TO CHRONOLOGY OF THE CROATIAN DINARIC KARST—A CASE OF THE PLITVICE LAKES

ABSTRACTKarst environments preserve some of the best archives of past climate, vegetation, hydrology, anthropogenic impact, and landscape evolution providing that a reliable chronology can be established. Here we present an example of the system of the Plitvice Lakes (Dinaric karst, Croatia), which is characterized by intensive tufa and lake sediment formations. The radiocarbon dating method, combined with some other dating methods and various geochemical and isotope analyses, showed that the Plitvice Lakes system in the present form has existed for about 8000 years. Older tufa deposits were dated to warm interglacial periods. A long-term comprehensive multi-proxy study showed that all environmental compartments (atmosphere, various water bodies, soil, bedrock, DIC, terrestrial and aquatic biota, and of course various secondary carbonates) must be included in order to obtain trustworthy results.

Quantitative evaluation of human and climate forcing on erosion in the alpine Critical Zone over the last 2000 years

Soil erosion is one of the main environmental threats affecting the Critical Zone (CZ) and thus ecosystem services and human societies. Through time, physical erosion is linked to both climate variations and the landscape evolution under long-term human pressures. In mountainous areas where erosion is highest a combination of large spatial and temporal approaches allows to assess the effect of these forcing factors on erosion rates. Here, we apply a retrospective approach based on lake sediments to reconstruct the long-term evolution of erosion in alpine landscapes. Lake Iseo in the Italian Alps acts as a natural sink for all the erosion products from a large catchment (1777 km2). This catchment is representative of the southern Italian Alps, where Holocene human activity and climate fluctuations are well known. The approach combines a source-to-sink method, using isotopic geochemistry (εNd, 87Sr/86Sr) associated to a multiproxy study of a lacustrine sediment section covering the last 2000 years. The applied method allows us to disentangle the role of climate and land use as erosion forcing factors through their differential impact on the various rock types present in the catchment. Indeed, the high-altitude part of the Iseo catchment, where glacier advances and retreats drive the erosion, presents isotopic signature different from those of the sedimentary rocks located in the lower part of the catchment, where both human activities and precipitations impacted erosion through time. A chronicle of glacial erosion over the last 2000 years was produced. Once the climatic trend was highlighted, the signal of erosion of sedimentary rocks was investigated to understand the influence of humans. From the Roman Period to the Industrial Age several periods of deforestation and increased human pressure were documented. The past sediment yield inferred for sedimentary rocks exhibits the highest values (>80 t km−2. yr−1) at periods of intense human practices. Hence, since the late Roman Period, human activities seem to be the dominant forcing factor of the physical erosion in mountainous environment of northern Italy. This study presents the first reconstruction through time of sediment yield derived from lake sediments associated with sediment sources identification and quantitative evaluation of the CZ erosion drivers.

Multi-Proxy Study of a Holocene Soil Profile from Romania and Its Relevance for Speleothem Based Paleoenvironmental Reconstructions

In this study, we describe a sedimentary deposit situated above Ascunsă Cave (SW Romania) that should be in depositional connection with coeval stalagmites from the cave. We excavated a 2.5 m deep soil profile and took contiguous bulk samples every 5 cm. Soil samples were analyzed for clay mineralogy, grain size, chemical composition, magnetic susceptibility, and stable carbon isotopes. Radiocarbon dating revealed that the soil is of Holocene age, and presents a depositional hiatus between 5.4 and 2.3 thousand years before the present. Due to the open system behavior of soils and mobility of organic matter, a few hundred years of uncertainty should be considered for the duration of this hiatus. The fine fraction is dominated by silt, while the clay mineralogical association is made of illite, chlorite, kaolinite, vermiculite, and illite–vermiculite and illite–chlorite mixed layered minerals. The sediment source of this soil is represented by a nearby mélange complex, as well as by an underlying terra rossa-type soil. As this latter type of soil is widespread in our study area, we performed luminescence dating on two samples from a representative location close to our site and it appears that this type of Mediterranean soil was formed during the Last Interglacial period. δ13C variability in soil organic matter and a stalagmite from the cave are comparing well, and could help future studies identify modifications in isotopic fractionation processes within the cave.

First modern human settlement recorded in the Iberian hinterland occurred during Heinrich Stadial 2 within harsh environmental conditions

As the south-westernmost region of Europe, the Iberian Peninsula stands as a key area for understanding the process of modern human dispersal into Eurasia. However, the precise timing, ecological setting and cultural context of this process remains controversial concerning its spatiotemporal distribution within the different regions of the peninsula. While traditional models assumed that the whole Iberian hinterland was avoided by modern humans due to ecological factors until the retreat of the Last Glacial Maximum, recent research has demonstrated that hunter-gatherers entered the Iberian interior at least during Solutrean times. We provide a multi-proxy geoarchaeological, chronometric and paleoecological study on human–environment interactions based on the key site of Peña Capón (Guadalajara, Spain). Results show (1) that this site hosts the oldest modern human presence recorded to date in central Iberia, associated to pre-Solutrean cultural traditions around 26,000 years ago, and (2) that this presence occurred during Heinrich Stadial 2 within harsh environmental conditions. These findings demonstrate that this area of the Iberian hinterland was recurrently occupied regardless of climate and environmental variability, thus challenging the widely accepted hypothesis that ecological risk hampered the human settlement of the Iberian interior highlands since the first arrival of modern humans to Southwest Europe.

Terrestrial records of the early Albian Ocean Anoxic Event: Evidence from the Fuxin lacustrine basin, NE China

The early Albian Oceanic Anoxic Event 1b (OAE 1b) is well documented in the Tethys, Pacific and North Atlantic, but few studies have evaluated whether or not terrestrial records of OAE 1b exist. In order to identify terrestrial records of the early Albian OAE 1b and to infer possible driving mechanisms, an integrated multi-proxy study from the late Aptian to Albian in the Fuxin lacustrine basin was conducted, including thick, organic-rich black mudstones, total organic carbon (TOC), organic carbon isotopes (δ13Corg), mercury concentration (Hg) and results from pyrolysis analyses (S2, Tmax and HI). Results show three distinct short-term negative δ13Corg excursions corresponding with relatively high TOC values, which could be counterparts of the Kilian, Paquier and Leenhardt sub-events of the early Albian OAE 1b. Atmospheric CO2 concentration (pCO2) recovered from C3 plant δ13Corg compositions indicates an increasing trend in Unit C during the early Albian, and there are three short-term increases of pCO2 corresponding to the three sub-events of OAE 1b at this time interval. We infer that a trend of increasing pCO2 during the Kilian sub-event in the study area is closely related to volcanism. Continental weathering calculated using chemical weathering indices (CIA, WIP and MIA(O)) show an increasing trend during the OAE 1b interval, likely resulting from warmer and more humid conditions. Mixed sources of terrestrial plants and lacustrine plankton demonstrated by pyrolysis analyses (HI vs. Tmax and S2 vs. TOC), indicate a terrestrial contribution to the organic-rich sediments of the Kilian, Paquier and Leenhardt sub-events of OAE 1b. We suggest that a CO2-forced greenhouse effect during the early Albian might have triggered the relatively warm and humid palaeoclimatic conditions, and intensified chemical weathering that combined to create high nutrient and organic matter levels that were flushed into lakes contributing to eutrophication and anoxia in lacustrine and in contemporaneous oceanic systems.

Development and degradation of a submontane forest in the Beskid Wyspowy Mountains (Polish Western Carpathians) during the Holocene

Mountain regions harbour high biodiversity; however, in numerous areas, they are strongly degraded by human activity. Our study reconstructs the development of the submontane forest belt (400 and 650 m a.s.l.) in the Beskid Wyspowy Mountains (Western Carpathians, Central Europe) affected by climate, humans, fire, and parasitic fungi during the Holocene. This forest belt is considered the most transformed by the human in the Carpathian region. Our multi-proxy study included analyses of pollen, non-pollen palynomorphs (NPPs), plant macrofossils, micro- and macrocharcoal (size fraction >100 µm, analysed in contiguous sampling), geochemical, and sedimentological markers. The results revealed that Picea abies dominated on the fen subjected to study at ca. 8510–5010 cal. BP. Tilia cordata was a substantial component of the submontane forest between ca. 8510 and 2970 cal. BP and it survived a probable Kretzschmaria deusta outbreak, as well as a period of increased fire activity (ca. 6000 cal. BP). The final retreat of forests with a substantial contribution of Tilia was induced by the expansion of Abies alba, Fagus sylvatica, and partly Carpinus betulus and was preceded by the period of increased fire activity and erosion. From ca. 900 cal. BP human-induced deforestations and agricultural and pastoral activity increased. The modern presence of woodlands with Pinus sylvestris and Larix decidua, in the submontane zone in the Beskid Wyspowy Mountains, is a result of sub-recent anthropogenic afforestation on overgrazed areas. The example of the Zbludza site reveals that changes related to fire and pathogen infections, if they have low magnitudes and new competitive taxa are absent, may be reversible in a forest composed of fire-intolerant tree taxa as Tilia. Nonetheless, the widespread submontane ecosystem degradation and the introduction of alien species hamper the regeneration of forest vegetation typical of the submontane zone.

Sea-ice, primary productivity and ocean temperatures at the Antarctic marginal zone during late Pleistocene

While Pleistocene glacial-interglacial cycles are commonly associated with strong waxing and waning of Northern Hemisphere ice sheets, the response of the Antarctic ice sheet and regional changes in oceanographic and environmental conditions to Pleistocene climate dynamics remain poorly constrained. We present a reconstruction of sea-ice cover, sea surface temperature and primary productivity off the Ross Sea margin (Adare Basin at the slope of the Drygalski Basin) during the marine isotope stages (MIS) 9 to 5 (350–70 thousands years ago, encompassing Terminations IV to II). Our multiproxy study relies on micropaleontology (diatoms, dinoflagellate cysts, benthic foraminifers), organic and inorganic geochemistry proxies (carbon and nitrogen isotopes, lipid biomarkers, XRF-data), and sedimentology (IRD) obtained from deep-sea core AS05-10. For each glacial-interglacial transition a clear succession of events can be observed: (near-)permanent sea ice cover during glacial stages is followed by ice-shelf break-up with episodic ice-free areas and surface water stratification. Notably, ice-shelf break-up precedes the increase in air temperature as measured in the Vostok ice core for each glacial-interglacial transition. Generally, air temperature over Vostok starts rising once sea-ice cover at site AS05-10 has significantly decreased, becoming seasonal, as indicated by the diatom species composition. This is also reflected by the high diatom productivity and increased water mixing at site AS05-10, which is indicative of its proximity to the Marginal Ice Zone. At the onset of Termination II (MIS6 to 5), high export productivity and dysoxic bottom water conditions occurred, while water temperature increased about 5 °C. During each interglacial spring/summer sea-ice cover is most reduced, and highest productivity occurs. Following each interglacial, the warm and cold fluctuations match the sawtooth character of the temperatures over Vostok. This record illustrates that at the Ross Sea margin, sea surface conditions and (export) productivity were strongly influenced by the natural climate variability of the Pleistocene. In light of this, current global warming may lead to increased ice-shelf break-up, water column stratification and shifts in the position/size of the Marginal Ice Zone with implications for algal species composition and diversity, and for primary productivity.

Control of depositional and diagenetic processes on the reservoir properties of the Mishrif Formation in the AD oilfield, Central Mesopotamian Basin, Iraq

The results of a multiproxy study on Mishrif carbonates from the margins of the Central Mesopotamian Basin of Iraq display a wide range of rock fabrics and diagenetic features, all affecting reservoir quality and flow properties in a complex manner. Based on petrographic and facies analyses of the Mishrif Formation in the AD oilfield, the model of a homoclinal ramp geometry with twelve characteristic microfacies types is proposed. A relevant observation is that the ramp, judging from the core data of the AD oilfield studied here, reflects low-energy conditions as documented by an abundancy of fine-grained carbonates in nearly all microfacies types. This notion is perhaps best understood in the context of an intrashelf basin with significant wave-seafloor interaction leading to wave degradation and a shallow effective wave base. In contrast to the rudist bioherms that typify the more basin-marginal settings, we find mainly evidence for small, low-relief buildups characterized by green algae. The Mishrif reservoir properties are shaped by two main diagenetic features: (i) early diagenetic, aquifer-related marine-meteoric mixing zone dissolution inducing abundant fabric selective porosity and (ii) the preferential cementation of Thalassinoides burrows leading to low-porosity concretionary carbonate nodules with reservoir properties that differ significantly from those of the host carbonate. Given the somewhat more distal position of the AD oilfield, the effects of prolonged stages of subaerial exposure related to sea-level fall, as reported from more basin marginal settings, are not recognized. The bending and splaying of seams around nodules and the well-preserved skeletal material within these concretionary carbonates demonstrate that the onset of nodule cementation was early diagenetic/pre-compactional in nature. Based on integrated microfacies and reservoir properties, seven rock types (i.e., Rock Type I-VII) with distinctive reservoir qualities are recognized. Nodular concretions are mainly developed in the Rock Type I lithology and result in distinctive cm-to dm-scale heterogeneity. The contrast between small, poorly-connected pore systems in nodules and medium-sized, well-connected pore systems in the host rock are best described as an inconspicuous, dual permeability system. Data shown here and evidence from other studies dealing with the Mishrif in the Central Mesopotamian Basin are important to understand and predict reservoir properties in other carbonate fields with similar properties.

Characterization of sedimentary organic matter and depositional processes in the Mandovi estuary, western India: An integrated lipid biomarker, sedimentological and stable isotope approach

A multiproxy study involving bulk (TOC, δ13Corg, grain size) and molecular (n-alkane biomarkers) analyses is used to investigate surface sediments from the Mandovi estuary in Goa, west coast of India to determine the origin, distribution and composition of organic matter (OM). The δ13Corg and n-alkane based indices (terrigenous/aquatic ratio (TAR) and Paq) indicate higher terrigenous OM accumulation in the river dominated upper reaches of the estuary. The presence of unresolved complex mixture (UCM), n-alkane indices (carbon preference index (CPI), average chain length (ACL), natural n-alkanes ratio (NAR)) and diagnostic isoprenoid ratios (pristane/phytane (Pr/Ph), Pr/n-C17, Ph/n-C18) helped to characterise intense human activity in the lower estuary. This conclusion is further supported by relatively high concentration of hopanes indicating petroleum contamination in the lower estuary. Furthermore, the study also highlights the important role of grain size on the distribution of OM along coastal margins, and provides detailed understanding of the variations in OM distribution/accumulation forced by natural processes and anthropogenic activities. The results of this study have significant implications for identifying natural and anthropogenic OM sources in estuarine systems especially in the context of increasing anthropogenic activities.

Middle Bronze Age land use practices in the northwestern Alpine foreland – a multi-proxy study of colluvial deposits, archaeological features and peat bogs

Abstract. This paper aims to reconstruct Middle Bronze Age (MBA; 1600–1250 BCE) land use practices in the northwestern Alpine foreland (SW Germany, Hegau). We used a multi-proxy approach including the analysis of biogeochemical proxies from colluvial deposits and buried topsoils in the surroundings of the well-documented settlement site of Anselfingen and off-site pollen data from two peat bogs. This approach allowed for in-depth insights into the MBA subsistence economy and shows that the MBA in the northwestern Alpine foreland was a period of establishing settlements with sophisticated land management and land use practices. The reconstruction of phases of colluvial deposition was based on ages from optically stimulated luminescence (OSL) and radiocarbon (AMS14C) dating from multi-layered colluvial deposits and supports the local archaeological record with the first phase of major colluvial deposition occurring during the MBA followed by phases of colluvial deposition during the Iron Age, the Medieval period and modern times. The on-site deposition of charred archaeobotanical remains and animal bones from archaeological features, as well as polycyclic aromatic hydrocarbons (PAHs), charcoal spectra, phytoliths, soil microstructure, urease enzymatic activity, microbial biomass carbon (Cmic) and heavy metal contents from colluvial deposits, were used as proxies for on-site and near-site land use practices. The charcoal spectra indicate MBA forest management which favored the dominance of Quercus in the woodland vegetation in the surrounding area north of the settlement site. Increased levels of 5β stanols (up to 40 %) and the occurrence of pig bones (up to 14 %) support the presence of a forest pasture mainly used for pig farming. In the surrounding area south of the settlement, an arable field with a buried MBA plow horizon (2Apb) could be verified by soil micromorphological investigations and high concentrations of grass phytoliths from leaves and stems. Agricultural practices (e.g., plowing) focussed on five staple crops (Hordeum distichon/vulgare, Triticum dicoccum, Triticum monococcum, Triticum spelta, Triticum aestivum/turgidum), while the presence of stilted pantries as storage facilities and of heat stones indicate post-harvest processing of cereal crops and other agrarian products within the settlement. In the area surrounding the settlement, increased levels of urease activity, compared to microbial biomass carbon (up to 2.1 µg N µg Cmic-1), and input of herbivorous and omnivorous animal faeces indicate livestock husbandry on fallow land. The PAH suites and their spatial distribution support the use of fire for various purposes, e.g., for opening and maintaining the landscape, for domestic burning and for technical applications. The off-site palynological data support the observed change in on-site and near-site vegetation as well as the occurrence of related land use practices. During the Early and Middle Bronze Age, fire played a major role in shaping the landscape (peak of micro-charcoal during the MBA), and anthropogenic activities promoted Quercus-dominated forest ecosystems at the expense of natural beech forests. This indicates a broader regional human influence in the northwestern Alpine foreland at low- and mid-altitude inland sites during the Middle Bronze Age.

Climate reconstructions based on GDGT and pollen surface datasets from Mongolia and Baikal area: calibrations and applicability to extremely cold–dry environments over the Late Holocene

Abstract. Our understanding of climate and vegetation changes throughout the Holocene is hampered by representativeness in sedimentary archives. Potential biases such as production and preservation of the markers are identified by comparing these proxies with modern environments. It is important to conduct multi-proxy studies and robust calibrations on each terrestrial biome. These calibrations use large databases dominated by forest samples. Therefore, including data from steppe and desert–steppe sites becomes necessary to better calibrate arid environments. The Mongolian Plateau, ranging from the Baikal area to the Gobi desert, is especially characterized by low annual precipitation and continental annual air temperature. The characterization of the climate system of this area is crucial for the understanding of Holocene monsoon oscillations. This study focuses on the calibration of proxy–climate relationships for pollen and glycerol dialkyl glycerol tetraethers (GDGTs) by comparing large Eurasian calibrations with a set of 49 new surface samples (moss polster, soil and mud from temporary dry ponds). These calibrations are then cross-validated by an independent dataset of top-core samples and applied to four Late Holocene paleosequences (two brGDGT and two pollen records) surrounding the Mongolian Plateau: in the Altai mountains, the Baikal area and the Qaidam basin, to test the accuracy of local and global calibrations. We show that (1) preserved pollen assemblages are clearly imprinted on the extremities of the ecosystem range but mitigated and unclear on the ecotones; (2) for both proxies, inferred relationships depend on the geographical range covered by the calibration database as well as on the nature of samples; (3) even if local calibrations suffer from reduced amplitude of climatic parameters due to local homogeneity, they better reflect actual climate than the global ones by reducing the limits for saturation impact; (4) a bias in climatic reconstructions is induced by the over-parameterization of the models by the addition of artificial correlation; and (5) paleoclimate values reconstructed here are consistent with Mongolia–China Late Holocene climate trends and validate the application of local calibrations for both pollen and GDGTs (closest fit to actual values and realistic paleoclimate amplitude). We encourage the application of this surface calibration method to reconstruct paleoclimate and especially consolidate our understanding of the Holocene climate and environment variations in arid central Asia.

Evaluating Holocene natural hazards in the French Massif Central from a regional lake sediment approach

Geophysical surveys in the Lakes Tazenat, Aydat, Chambon and Lacassou combined with a multiproxy study of sediment cores highlight Late Holocene abrupt environmental changes in the northern part of the French Massif Central (FMC). Dating landslide-induced dust layers and subaqueous slope failures impacting lake basin sedimentary fills suggest regional triggering by palaeo-earthquakes (cluster of events) either in the Puy-de-Sancy volcano area, or along the regional Limagne fault. In the present study, a cluster of palaeo-earthquakes occurring in the Sancy area between AD 1243 and 1270 are documented in the Lakes Montcineyre, Chauvet, Pavin and Guéry, as well as by the formation of Lake Lacassou following the last emplacement of the Dent du Marais landslide in the Chaudefour glacial valley around AD 1250 ± 30. Former cluster of earthquakes occurring near the Limagne fault between AD 580 and 650 are evidenced in Lake Tazenat and in maar Lake Pavin. Lake Pavin present lake-level was similarly favoured by the cluster of earthquakes between AD 1243 and 1270 and the occurrence of a slump and an outburst flood event resulting in the bypassing of a palaeo-outlet. Holocene earthquakes near the Limagne fault are suggested in maar Lake Tazenat by coeval mass wasting deposits (MWDs) around 2250 ± 50 cal. BP and around 2730 ± 30 cal. BP. A landslide-induced dust layer dated between 2760 and 2520 cal. BP at the transition from paludal to lacustrine deposits in the Chaudefour glacial valley is suggesting that the formation of Lake Chambon resulted from a first emplacement of the Dent du Marais landslide. Radionuclides and radiocarbon dating in Lake Tazenat suggest variable sedimentation rates over the last millennia due to: (i) floods during the Little Ice Age, (ii) coeval MWDs at the basin edges and an erosive turbidite in the central basin between AD 575 and 625, and (iii) lake eutrophication since AD 1945. More gravity cores are needed to directly sample and date the youngest generation of coeval MWDs detected on seismic profiles in order to test the impact in this lake of the cluster of major historical earthquakes in the FMC between AD 1450 and 1490 near the Limagne fault.

Late Pleistocene chronology and environment of woolly rhinoceros (Coelodonta antiquitatis (Blumenbach, 1799)) in Beringia

Uncertain chronology and data scarcity have impeded realistic reconstructions of megafauna extinctions in the Late Pleistocene in several key regions of the Northern Hemisphere such as Beringia. This region was a refuge for several plants, animals during the extremely cold period of the Late Pleistocene in high Arctic latitudes. The woolly rhinoceros was one of the most widespread members of the megafauna in the Asiatic part of the region (West Beringia) between ∼60 and 14 cal ka BP. This study is based on statistical analyses of 20 newly obtained and 110 previously published radiocarbon dates. We found three large “waves” in the woolly rhinoceros range changes separated between themselves by the cold climatic Heinrich events (H2 and H4). The chronology of the woolly rhinoceros was overlaid on data of environmental changes obtained basing on 504 generalized early published pollen spectra throughout the species range and, separately, outside the range – in the east of the West Beringia realm and in East Beringia. In general, milder environmental conditions of MIS3 (57–29 ka BP) were more favourable for the woolly rhinoceros than the harsh conditions of the Last Glacial Maximum (∼29–15 cal ka BP) in MIS2. We have concluded that the feed base was unlikely the main limiting factor in the distribution of woolly rhinoceros in Western Beringia, and other ecological factors (temperature/precipitation) determined the species range and its oscillation over the MIS3–MIS2 stages. Based on summarizing available data and this research, we have proposed that there were sets of different reasons that prevented the woolly rhinoceros migration to the east of Beringia in different periods of the Late Pleistocene. Abrupt woolly rhinoceros extinction in Beringia between 15 and 14 cal ka BP coincided with the Bölling warming and the Older Dryas cooling. The ecological situation just before the extinction, associated with climate warming, moisture increasing and shrub tundra expansion in West Beringia, was qualitatively different from previous cases of the species range degradations in the second half of the Late Pleistocene. This multi-proxy study of woolly rhinoceros chronology provide a new basis for further understanding of its population history, demography, and biology in Beringia before its extinction.

Quantification of Lithological Heterogeneity Within Opalinus Clay: Toward a Uniform Subfacies Classification Scheme Using a Novel Automated Core Image Recognition Tool

The Opalinus Clay is notable in Switzerland as being the selected host rock for deep geological disposal of radioactive waste. Since the early 1990’s, this argillaceous mudstone formation of Jurassic age has been intensively studied within the framework of national and international projects to characterize its geological, hydrological, mechanical, thermal, chemical, and biological properties. While there is no formal stratigraphic subdivision, the Opalinus Clay lithology is classically divided into several, dam- to m-scale sub-units (or facies), depending on location. Recent multi-proxy studies (combining petrographic, petrophysical, geochemical, and mineralogical analyses) have however demonstrated that high, intra-facies, lithological heterogeneity occurs at the dm- to cm-scale. To constrain this small-scale heterogeneity into distinct lithological units (subfacies), the present study aims at defining and presenting a convenient subfacies classification scheme covering the overall Opalinus Clay lithology across northern Switzerland. Petrographic (macro- and microfacies), mineralogical (X-ray diffraction) and textural (image analysis, machine learning and 3D X-ray computed tomography) analyses are performed on diverse drill cores from the Mont Terri rock laboratory (northwestern Switzerland), and results are extended further to the east (Riniken, Weiach, and Benken). Most of the investigated Opalinus Clay can be described by the use of five distinctive subfacies types (SF1 to SF5), which are visually and quantitatively distinguishable by texture (grain size, bedding, fabric, and color) and composition (nature and mineralogy of components). The five subfacies types can be further refined by additional attributes and sedimentary characteristics (biogenic, diagenetic, and structural). Eventually, the widespread and consistent use of standardized Opalinus Clay subfacies types provides the means to harmonize petrographic descriptions within multidisciplinary research projects, enhance reproducibility of in situ experiments, and further evidence the tight relations between lithology and various rock properties.

Provenance and compositional variations of intra-caldera lake sediments at La Primavera, Jalisco, Western Mexico

The multi-proxy provenance analyses carried out in the Upper Pleistocene sediments of the La Primavera intra-caldera paleolake in western Mexico document the evolution of source areas. This lake formed a few thousand years after the caldera collapse (~95 ka) and lasted until the intra-caldera resurgence process that ended 75 ka ago. Between 93.8 and 71 ka the sedimentary succession that filled the lake was affected by the extrusion of domes at its central part and the constant influx of volcaniclastic debris. Ring-fault domes and extra-caldera activity sourced at San Miguel volcano provided additional volcanic debris into the lake. Based on our multi-proxy studies and recent age determinations of the post-caldera activity is likely that the paleolake was coggled at 78 ka in the central sector of the caldera, synchronously with the caldera resurgence. The resulting deposits (volcaniclastic debris) are tuffaceous sands characterized by lithoarenites rich in neo-volcanic grains, mainly vitrophyric and felsitic volcanic fragments with similar characteristics to the rocks of the Ixtahuantonte, El Nejahuete composite dome, Cerro Alto, Las Pilas, and Dos Coyotes domes. Geochemically, the sediments of the La Primavera caldera exhibit concentrations and elemental relationships of major and trace elements similar to the average of the upper continental crust. However, the high concentrations of some elements, such as La, Th, Ti, and Zr are related to the hyperalkaline nature of the magmatism that originated this volcanic caldera. The concentrations of SiO2/Al2O3, Na2O/K2O, Th, Sc, and Zr/10 indicate a passive margin tectonic setting deposition under low weathering conditions.

Palaeoclimatic and sea-level fluctuations from the last deglaciation to late Holocene from western India: Evidence from multiproxy studies

• At least 4 episodes of marginal marine sedimentation environments are reported between last deglaciation to the late Holocene in Western India.. • The first phase of deposition under marine influence is at ~20 ka BP, the second phase between ~11,210 and 9759 cal yr BP and third phase of sea level rise at around ~6118 cal yr BP. The final phase of marine to marginal marine conditions are noted to be of post ~2650 ± 180 cal yr BP until ~1530 ± 350 cal yr BP. • There were coeval dry climatic conditions of the Older Dryas and Younger Dryas periods besides the warm and humid conditions of the Bolling-Allerod period. • During the last deglaciation to late Holocene times, at several times the Gulf of Kachchh extended inland and the rivers debouched into these extended gulfs rather than in the Little Rann as seen at present. A sediment core from a palaeochannel distributary of the Saraswati River basin in western India was investigated through a multi-proxy study using palynology, phytoliths, sedimentology, geochemistry, magnetic mineralogy and chronology. The site is located at the eastern margin of the Little Rann of Kachchh in the northwestern part of the Gujarat Alluvial Plains. The goal was to reconstruct the paleoclimatic and sea level flucutations spanning from the last deglaciation to the late Holocene in the area. The core records suggest at least four episodes of marginal marine environment between the last deglaciation and the late Holocene. The first phase of sediment deposition under marine influence was observed post LGM. The signatures of coeval dry climatic conditions of Older Dryas and Younger Dryas periods besides warm and humid conditions of Bølling-Ållerød period are reflected in the core records. The second phase of rise in sea level occurred between ~11,210 and ~9795 cal yr BP, which falls within the period of high gradient of sea-level rise of western India. The third phase of global sea level rise in the area is at around ~5747 cal yr BP which coincides with a high sea level phase along the west coast of India. The final recurrence of sediments with predominant marine signatures post ~2650 ± 180 cal yr BP until ~1530 ± 350 cal yr BP suggests marine to marginal marine conditions in the area.

Multi-Proxy Records of Late Holocene Flood Events From the Lower Reaches of the Narmada River, Western India

Analyses of a fluvial sedimentary sequence from the lower reaches of the Narmada River establish a record of rhythmic cycles of sediment facies that represent floods during the late Holocene. The south-west Indian monsoon strongly influences the study area, and heavy rainfall or cyclones which originate from either the Bay of Bengal or the Arabian Sea, also affect the region. Optically stimulated luminescence dating places the 8 m thick sediment sequence in the climate transition phase which ranges from the Medieval Warm Period to the Little Ice Age. Multi-proxy analyses including high-resolution granulometry, magnetic susceptibility, ferromagnetic mineral concentration, facies major oxide geochemistry, and micro-fossil records (from two sedimentary units) are used to study these late Holocene flood events. The latter are characterised by multiple sediment facies, depositional events, changes in channel morphology, and distinctive flood signatures. Integration of these records enables to identify two distinct aggradations viz. phase I and phase II, as well as a relative change in channel morphology. The study describes 11 flooding events and their imprints over multi-proxy records. Historic documents and instrumental records from the town of Bharuch referring to floods, movement of channel sand, channel shallowing, and the dysfunction of the ancient port of Bharuch further validate the inferences drawn from the sedimentary sequence. The study exemplifies the need to use high resolution and multi-proxy studies to interpret paleoflood records and climate signatures in order to build archives of monsoonal rivers.

Unveiling the relevance of carbohydrate-rich underground plant foods in the archaeological record

Rich in carbohydrates, underground storage organs played a key role in human history. This project aims to establish a systematic methodology for their multi-proxy study, creating an online reference collection, using different microscopy techniques for identification and establishing a reference guide to use-wear patterns on experimental archaeology tools used for the processing of underground storage organs.