Multi-proxy Analysis Research Articles

Forest and lake dynamics in response to temperature, North American monsoon and ENSO variability during the Holocene in Colorado (USA)

Learning how terrestrial environments responded to past temperature and precipitation variations can help anticipate how these environments will respond to natural climate variability upon which human induced climate change is superimposed. Here we present a detailed multi-proxy analysis of a sediment core from Emerald Lake, located at the montane-subalpine forest transition in west-central Colorado. The record tracks changes in the lake environment, vegetation and fire activity mostly related to climate change for the latest Pleistocene and Holocene, and complements the previously published lake-level reconstruction from the same site. Vegetation and lake level show similar patterns with insolation changes and other regional paleoclimate records for temperature, with coldest conditions during the Younger Dryas (YD), warming in the early Holocene - thermal maximum reached around 6800 cal yr BP – and cooling in the middle and late Holocene. This record also shows how subalpine environments reacted to Holocene moisture dynamics for both summer, related to the North American Monsoon (NAM), and winter precipitation that could be associated with El Niño Southern Oscillation (ENSO), indicating that Emerald Lake was sensitive to long-term and millennial-scale regional and global climate changes. Climatic perturbations, generally cold and/or arid events and low lake levels at ca. 8200, 4200, 1200-1000 cal yr BP influenced the vegetation around Emerald Lake in association with well-known worldwide climatic events.

Multi-proxy analysis of organic matter accumulation in the Upper Ordovician–Lower Silurian black shale on the Upper Yangtze Platform, south China

Abstract There is no doubt that organic matter plays an important role in shale gas accumulation and storage. Thus, successful evaluation and production strategies of organic-rich shale deposits require an understanding of the range of factors that contribute to the accumulation and preservation of organic matter in these deposits. This paper reports results of a multi-faceted study of two Ordovician–Silurian transition sections of the Upper Yangtze Platform of South China. Organic and inorganic geochemical data are used to reconstruct paleoenvironmental changes across this critical interval of Earth history and to identify those factors that were most important to organic matter accumulation. Deposition of organic-rich shale of the Katian lower Wufeng Formation was favored by rising sea level and diminished clastic sediment content. Black shale of the upper Wufeng preceded Hirnantian glaciation whereas the overlying lower Longmaxi Formation accumulated in association with a post-glacial rise of sea level as well as the peak of Caledonian tectonism. The carbonaceous deposits appear to reflect the combined effects of elevated primary productivity as suggested by Si/Al and Ti/Al ratios, especially in the upper Wufeng, and consequent depletion of water column oxygen (preservation). Consideration of the relationships of redox-sensitive trace element concentrations and total organic carbon content suggest that bottom water conditions fluctuated between anoxic and euxinic during this period, perhaps related to rapid oscillations of sea level. Moreover, the basin appears to have remained connected with the global ocean in spite of Caledonian uplift of bordering areas. Thus, black shale sedimentation on the Upper Yangtze Platform at the Ordovician-Silurian boundary reflects the interplay of climate change and tectonism and their influences on sea level, clastic sediment content, and paleo-productivity.

Late-Glacial Paleoecology of the Middle Susitna Valley, Alaska: Environmental Context for Human Dispersal

We present here the results of multi-proxy analyses (sediment geochemistry, diatoms, and pollen) from sediment cores collected at four lakes in the middle Susitna Valley, Alaska. These lakes form a transect from the tundra to the boreal forest. The retrieved cores span from ~12,000 cal yr BP to the present, with age control provided by radiometric dates and tephra deposits, some of which are newly identified. Results indicate that deglaciation occurred before 12,000 cal yr BP and that by that time, the lakes were deep, productive, and surrounded by shrub tundra. The lake with the highest sampling resolution indicates a brief climatic reversal ~11,500 cal yr BP with decreased diatom-inferred lake level and lowered lake productivity, and reduced shrub presence. During the early to middle Holocene, all of the sedimentary records provide evidence of climatic amelioration with tree expansion and productive lakes. A middle to late Holocene climatic deterioration with reduced trees and a shallower, less productive lake is also indicated. In addition, the prominent Watana tephra at ~4,000 cal yr BP likely reduced lake productivity and affected the vegetation. Even though the region was relatively productive soon after deglaciation, people did not occupy the region until ~11,000 cal yr BP, about 1000 years later, and then only sparsely. By the middle and late Holocene, the region was more densely populated and this shift in human occupancy presumably reflects changes in resource abundance, especially caribou. Whether the Watana ashfall influenced caribou abundance and thus people, is still under investigation, but given the tephra’s effect on vegetation and lake productivity, it seems likely.

Climate and vegetation changes in coastal ecosystems during the Middle Pleniglacial and the early Holocene: Two multi-proxy, high-resolution records from Ría de Vigo (NW Iberia)

Abstract New multi-proxy analyses were performed on two sedimentary sections from shallow marine ecosystems of Ria de Vigo (NW Iberia) to study the effects of the MIS-3 and early Holocene environmental variability. High-resolution data (microfossils, sedimentary facies, and geochemistry) allowed performing a comprehensive reconstruction of the main environmental changes (climate, vegetation, hydrology and sea level) that occurred during part of the MIS-3 period (57.0–38.8 cal ka BP) and the early Holocene (11.2–7.0 cal ka BP). The chronology is supported by isotopic dating and the correlation of pollen data with other regional palaeo-climatic records. Several phases characterised by increasing pollen representation of deciduous Quercus alternate with others marked by increasing representation of heliophytes that may reflect the succession of Interstadials (GI) and Stadials (GS) described in Greenland ice cores. In addition, dinoflagellate cysts and diatoms reflect conditions in the marine environment (SST and productivity). New palynological data confirms that coastal ecosystems of Atlantic Iberia were sensitive to the main climatic oscillations affecting the North Atlantic. It also suggests that pinewoods, juniper communities and mesophilous deciduous forests with Carpinus betulus L. (which shows exceptionally high pollen abundances for the MIS-3) persisted in the surroundings of Ria de Vigo until ~7500 a BP. For the first time in this region, we describe the effects of an abrupt episode of cooling that may correspond to Bond cycle 7 (10.5 ka event).

The changes of hydrological environment recorded in the section of Tianluoshan Site in Zhejiang Province

The Tianluoshan Site of Yuyao City in Zhejiang Province is a typical Neolithic site with a complete preservation of the Hemudu culture (ca. 7–5 ka). This culture is well-known for its important role in studies on early rice domestication. Studying samples from the Tianluoshan Site provides a good opportunity to understand regional paleoenvironmental changes and their impact on Neolithic settlement. In this study, 263 cm samples were obtained from the T005W profile in the Tianluoshan Site Museum. The profile samples were subjected to lithologic stratigraphic description, accelerated mass spectrometry (AMS)14C dating, high-resolution X-ray fluorescence (XRF) spectrometry, elemental scanning (2 mm/sample), diatom (20 cm/sample) and particle size analysis (2 cm/sample). The paleoenvironmental changes reflected by this profile could be divided into three stages based on multi-proxy analysis. (1) In the first stage (263–211 cm, about 7.0–6.5 cal ka BP), or the first and second cultural periods of Hemudu, the cultural layer was stacked and mixed with high contents of sand, gravel, and pottery pieces, thereby showing obvious disturbance from human activities. The diatom assemblage was dominated by aerophilous species, such as Hantzschia amphioxys , which live in shallow swamp. These findings indicated that this period was dominated mainly by a freshwater swamp environment. The geomorphic condition provided Neolithic people with a suitable environment to colonize and develop rice cultivation. (2) In the second stage (211–28 cm, around 4.2–4.0 cal ka BP), the layer had a thickness of approximately 180 cm. However, five AMS 14C dates from this stage were between ca. 4.2 and 4.0 cal ka BP, and the lithology of these overlying strata were inconsistent with the cultural layer underneath. As such, a hiatus existed between the two stages. The lithological feature of this stage mainly consisted of a parallel layer with a couplet of interbedded clay silt and white-gray sand layer, which represented deposition under hydrostatic conditions after flooding. This part also contained multiple yellow oxide layers, possibly indicating transient exposure. The intensity of Ca between 211 and 166 cm was low, but this value increased rapidly above 166 cm and stabilized at a higher level than that of the first period. The dominant diatom assemblage changed from a freshwater group ( H. amphioxys ) at the bottom of this part to a marine and brackish group (e.g., Cyclotella striata var. striata and Actionptychus undulates ). In this period, the rapid deposition of flooding events likely occurred as initiated by heavy precipitation (211–166 cm), which was indicated by low Ca and freshwater aerophilous diatom assemblage. Afterward, multiple storm surges resulted in sedimentation (166–50 cm) with marine-brackish characteristics. (3) In the third stage (28–0 cm, no date), the layer was characterized by a mixture of brown clay, silt, sand, and gravel with low contents of water, iron, and manganese oxide spots. Ca was weak, and clay content was high. This period was mainly dominated by freshwater epiphytic diatom species, such as Pinnularia vividis and Navicula cuspidate , and affected by modern farming. This study revealed the background of the hydrological environment during the first and second cultural periods of the Tianluoshan Site and the flooding events around 4.2–4.0 cal ka BP, which were essential for the understanding of the environmental background of Neolithic people and the extreme regional events in the Tianluoshan Site. The stratigraphic deposits of different sections in the site varied because of the influence of microtopography. Therefore, studies on the paleoenvironment of the Tianluoshan Site should involve a systematic analysis of multiple sections and cores around this site.

Biogeochemical cycling and ecological thresholds in a High Arctic lake (Svalbard)

Lakes are a dominant feature of the Arctic landscape and a focal point of regional and global biogeochemical cycling. We collected a sediment core from a High Arctic Lake in southwestern Svalbard for multiproxy paleolimnological analysis. The aim was to find linkages between the terrestrial and aquatic environments in the context of climate change to understand centennial-long Arctic biogeochemical cycling and environmental dynamics. Two significant thresholds in elemental cycling were found based on sediment physical and biogeochemical proxies that were associated with the end of the cold Little Ice Age and the recent warming. We found major shifts in diatom, chironomid and cladoceran communities and their functionality that coincided with increased summer temperatures since the 1950s. We also discovered paleoecological evidence that point toward expanded bird (Little Auk) colonies in the catchment alongside climate warming. Apparently, climate-driven increase in glacier melt water delivery as well as a prolonged snow- and ice-free period have increased the transport of mineral matter from the catchment, causing significant water turbidity and disappearance of several planktonic diatoms and clear-water chironomids. We also found sedimentary accumulation of microplastic particles following the increase in Little Auk populations suggesting that seabirds potentially act as biovectors for plastic contamination. Our study demonstrates the diverse nature of climate-driven changes in the Arctic lacustrine environment with increased inorganic input from the more exposed catchment, larger nutrient delivery from the increased bird colonies at the surrounding mountain summits and subsequent alterations in aquatic communities.

First palaeoecological evidence of buffalo husbandry and rice cultivation in the Kerinci Seblat National Park in Sumatra, Indonesia

Rice is one of the most important subsidence crops, however evidence of the origin and domestication of rice cultivation is still scarce in Indonesia. This study aims to trace the beginning of rice cultivation and buffalo husbandry in Sumatra, Indonesia. We carried out palaeoecological multi-proxy analyses of pollen and spores, non-pollen palynomorphs (NPPs) and macro-charcoal analysis on a sediment core from the swamp forest of Danau Bento (DB) in the Kerinci Seblat National Park (KSNP). Our results provide first evidence of buffalo husbandry in the Kerinci at least 4,300 years ago, in line with the migration of the Austronesians to Sumatra. NPPs and pollen results indicate the existence of grassland until about 3,200 cal bp around the site, which was used for buffalo grazing and not for rice cultivation. The rise of Poaceae about 2,500 cal bp suggests the beginning of rice cultivation in the swamp contemporary with a decline in grazing as shown by the NPPs. However, this phase lasted only few centuries until ca 2,100 cal bp. Following the decline of rice cultivation, the swamp remained in use as a grassland for grazing.

Age and pattern of the southern high-latitude continental end-Permian extinction constrained by multiproxy analysis

Past studies of the end-Permian extinction (EPE), the largest biotic crisis of the Phanerozoic, have not resolved the timing of events in southern high-latitudes. Here we use palynology coupled with high-precision CA-ID-TIMS dating of euhedral zircons from continental sequences of the Sydney Basin, Australia, to show that the collapse of the austral Permian Glossopteris flora occurred prior to 252.3 Ma (~370 kyrs before the main marine extinction). Weathering proxies indicate that floristic changes occurred during a brief climate perturbation in a regional alluvial landscape that otherwise experienced insubstantial change in fluvial style, insignificant reorganization of the depositional surface, and no abrupt aridification. Palaeoclimate modelling suggests a moderate shift to warmer summer temperatures and amplified seasonality in temperature across the EPE, and warmer and wetter conditions for all seasons into the Early Triassic. The terrestrial EPE and a succeeding peak in Ni concentration in the Sydney Basin correlate, respectively, to the onset of the primary extrusive and intrusive phases of the Siberian Traps Large Igneous Province.

Holocene hydroclimate and environmental change inferred from a high-resolution multi-proxy record from Lago Ditkebi, Chirripó National Park, Costa Rica

Multi-proxy analysis of a sediment core recovered from Lago Ditkebi in Chirripó National Park, Costa Rica, was undertaken to develop a multi-decadal to sub-centennial-scale reconstruction of Holocene hydroclimate and environmental change for the region. Analyses of sub-fossil chironomid assemblages, macroscopic charcoal, and bulk sediment geochemistry suggest that the glacial highlands in Chirripó National Park experienced notable hydroclimate variability, periodical burning by wildfires and climate-related vegetation change during the last ~8100 years. A single chironomid taxon, Procladius, most commonly associated with cold glacial lakes in Costa Rica, dominates the Holocene sub-fossil chironomid assemblage in Lago Ditkebi. Inferred from the proxy records, the interval between ~8100 and 5270 cal yr BP at the glacial highlands was relatively cold and dry with low effective moisture and limited fire activity. Cool and dry conditions were also observed between ~2820 cal yr BP and present but co-occurred with more frequent, low-severity fires. The highest fire frequency occurred between ~3300 and 1600 cal yr BP. The shifts in the chironomid assemblage and the low δ13C values detected between ~5270 and 2820 cal yr BP suggest a warm and wet climate and a decrease in abundance of Muhlenbergia, a C4 grass during that time. Concurrent maxima in C/N, charcoal accumulation and the abundance of thermophilous chironomid taxon, Polypedilum N type, at ~5200 cal yr BP are indicative of an abrupt climate change event that was characterized by rapid warming, quickly increased effective moisture and intense wildfires in the glacial highlands of Costa Rica.

A Lower Pleistocene to Holocene terrestrial record from the Eskişehir Graben (Central Anatolia): Paleoclimatic and morphotectonic implications

As one of the rare terrestrial archive with continuous sedimentation back to almost 1 Ma in Anatolia, the Eskişehir Graben was investigated in outcrops and cores by multi-proxy analysis regarding chronology and paleoclimatology. The present study comprises significant implications for both the impact of climate changes on fluvial systems in the timescales of the Milankovitch band and the controversial age and rate of the crustal extension in western Anatolia. Our findings indicate that LOI950 and δ18Ocarb, which are indicators for the amount of soil carbonate and paleo-temperature respectively are collectively capable of distinguishing between glacial and interglacial periods in the predominantly floodplain deposits of the graben infill. Secondarily, LOI550 and δ13Ccarb values further help this discrimination via primary production and composition of vegetation cover respectively. Pollen data, albeit highly discontinuous due to poor preservation under subaerial conditions, point out a steppe-like vegetation cover where the forest components expand particularly in the wet interglacial periods. In the other hand, the chronological frame provided by astronomical calibration of certain proxy-records strongly suggest that the Eskişehir Fault Zone initiated as a boundary fault of a half-graben some 900 ka. The rate of vertical movement on its southern branch since the last 70 ka is unexpectedly high (2.3 mm/a), a phenomenon that requires urgent risk assessment analysis in the vicinity of the Eskişehir city.

Mid and Late Holocene evolution of Brateș Lake region (Danube floodplain) based on the multiproxy analysis

This study proposes a local paleo–landscape reconstruction of the Danube floodplain based on a stratigraphic sequence retrieved from Brateș Lake which, by its emplacement near the confluence of Danube – Prut rivers, was fully receptive to changes associated to hydrological, geomorphological or anthropogenic driven events. Due to its intermediate position within the Lower Danube valley Brateș Lake is a proxy for the evolution of Cotul Dunării area (the region of Danube valley turning from S–N to W–E direction) and provide valuable information about the timing of Danube river advancement to the Black Sea after its reconnection to World Ocean. The sediments were analysed to get the history of their deposition by means of accelerator mass spectrometry (AMS) 14C dating, grain–size parameters, organic matter and carbonate content, magnetic susceptibility together with paleo–fauna and pollen content which altogether led to the identification of main stages: i) delta front advance into Danube estuary (before 8000 BP), ii) shoreline foreshore deposits which describe shoreline position (8000–7900 yrs BP), iii) river floodplain development (7900–5300/5000 yrs BP), iv) lake formation (5300/5000 yrs BP – present).

A 4700-year record of hydroclimate variability over the Asian monsoon intersection zone inferred from multi-proxy analysis of lake sediments

Abstract The sedimentology, geochemistry, and plant microfossils of volcanic lake sediments from Cambodia were analysed to reconstruct a 4700 year record of change in moisture availability. This site sits at the heart of the intersection zone of the East Asian and Indian summer monsoons – a climatic system that is socio-ecologically important but poorly understood. Proxies for lake deepening and shallowing indicate a stepwise weakening of the summer monsoon from c. 4700 to 1700 cal. years BP, after which it appears to gradually strengthen. This trend is punctuated by seven dry events between 4300 and 1540 cal. years BP. The results present one of the longest, continuous records of palaeo-hydrological change in the Asian monsoon intersection zone. In doing so, they suggest that the climate of the region was broadly comparable to the East Asian summer monsoon (EASM) province to approximately 2240 cal. years BP, and the Indian summer monsoon (ISM) province between 2240 and 1700 cal. years BP. The subsequent, late Holocene hydroclimate appears to reflect a combination of both subsystems. These findings highlight dynamism in EASM and ISM dominance over mainland southeast Asia over the past five thousand years, but overall demonstrate regional vs. local scale influence on the hydroclimate of the region. The multi-decadal periods of strong drying that punctuate longer-term monsoon patterns demonstrate the natural variability of the mid- to late- Holocene climate of the intersection zone. This is of consequence given that apparently less severe drought events of the last millennium have had dramatic socio-economic consequences. Resultantly, planning for the resilience of socio-ecological systems within the region needs to account for the real potential of similar scale events occurring in the future, particularly given the increased extremes predicted for Asian summer monsoon region over the 21st century.

Agrarian landscapes in the Iberian Iron Age: Mountain communities and land use in southeastern Iberia

AbstractAgrarian landscapes are among the least understood features of first millennium B.C. societies in the western Mediterranean. Studies of such landscapes in the context of the Iberian Iron Age have been based essentially on the archeological record in places used for purposes other than farming, particularly settlements and areas reserved for burials and rituals, or on the identification of the possible use of fertilizers. Here we present a multiproxy analysis of an agrarian landscape based on geoarchaeological and paleoenvironmental studies in a mountainous region in southeastern Iberia. The findings confirmed the existence of farmland cultivated as early as the first millennium B.C. in the high Jutia Valley in the Spanish province of Albacete. These results suggest that coordinated analyses can be highly useful for identifying enduring agricultural practices, while contributing to a fuller understanding of western Mediterranean agrarian landscapes and their millenarian resilience, attributable to the coevolution of human communities and the environment.

A multi-proxy shallow marine record for Mid-to-Late Holocene climate variability, Thera eruptions and cultural change in the Eastern Mediterranean

The River Nile catchment is considered the major source of nutrient-rich freshwater and sediment draining into the eastern Mediterranean Sea. Thus, exceptional high-resolution record from the Nile Littoral Cell likely traces changes in the Nile outflows related to climatic changes driven by the monsoonal system. This study used multi-proxy analyses combining sedimentological, geochemical and organic stable isotope data along with foraminiferal data in a southeastern Levantine inner shelf sedimentary sequence to understand Mid - to Late Holocene northeast African climate variability. The palynological record is used to reconstruct local scale changes in the regional vegetation related to the Mediterranean climate system. The analyzed records reveal multi-decadal to centennial pacing of paleoceanographic and paleoclimatic changes, with most prominent events recorded at 4.28, ∼3.6 and at 2.9 kyr BP.These transitional periods characterized by simultaneous high δ15N values and low total organic carbon (TOC) suggest drier climatic conditions, decrease in Nile discharge, leading to lower nutrient supply. A stable and arid climate during Mid-Late Holocene (∼4.5–3.6 cal kyr BP) associated with a weaker monsoon system as well as with a weaker Mediterranean climate system is indicated based on high and constant sedimentation rates (∼400 cm kyr−1), along with relatively stable values and only occasional weak fluctuations documented in all of the proxies. This climatic pattern is punctuated by a peak in maximum aridity at 4.28 kyr BP evidenced by low TOC value and low arboreal pollen (AP) and Artemisia/Chenopodiaceae (A/C) pollen ratios and the sharp decline in the abundance of benthic foraminifera Cribroelphidium poeyanum and Valvulineria bradyana. This change corresponds with the well-studied 4.2 kyr BP drought event in the Middle East, Mesopotamia and south Asia.During the late Holocene (∼3.6–2.8 cal. Kyr BP) the climate became unstable characterized by shifts between relatively wetter and drier conditions as evident in considerable fluctuations in all proxies. Maximum positive excursions of TOC values, C/N ratio along with high dominance of opportunistic foraminiferal species (e.g., Ammonia tepida) indicate northeast African wetter conditions and increased Nile discharge at 3.5, 3.3, 3.2 and 3.0 kyr BP. The distinct and abrupt transition from a stable to an unstable climate regime around 3.6 kyr BP may have been influenced by the Thera volcanic eruption. Thus, the sedimentary record investigated in this study may provide evidence for the impacts of this well-known volcanic eruption not just on the climate regime in the Levant but also on the ancient Near East and Egypt.

A new multi-proxy record of environmental change over the last 1000 years on Chiloé Island: Lake Pastahué, south-central Chile (42°S)

Knowledge of past environmental and climatic conditions of lake ecosystems on Chiloé Island on a millennial scale is limited. Hence, this study fills a gap in our understanding of this part of southern Chile. The aim of this study was to reconstruct the environmental and climatic history of the last 1000 years of Lake Pastahué through a multi-proxy sediment core analysis. The 1-m-long core was subsampled every centimeter for the organic matter, magnetic susceptibility, grain-size distribution, and biological indicator (pollen, chironomids) analyses. The age model was constructed from 210Pb, 137Cs, and 14C activity. Pollen results revealed a North Patagonian forest composition represented by Nothofagus, Weinmannia, Drimys, Tepualia, Myrtaceae, Poaceae, and Pteridophyta. The abundance of Rumex and Pinus in the most recent part of the pollen assemblage reflects a clear anthropogenic impact. The sedimentological parameters and chironomid assemblage show similar variations, which highlight changes in the trophic state of the lake. The changes observed in all proxies suggest the influence of climate events such as the ‘Medieval Climate Anomaly’ (MCA) and ‘Little Ice Age’ (LIA). The variations observed since the beginning of the 20th century could be the result of the combined effect of anthropogenic activities and the increase in temperature recorded in south-central Chile and Patagonia.

A multi-proxy quantitative record of Holocene hydrological regime on the Heixiazi Island (NE China): indications for the evolution of East Asian summer monsoon

The Holocene hydrological regime on the Heixiazi Island is critical for understanding the evolution of the East Asian summer monsoon (EASM) for the island’s climate-sensitive location on the northern fringe of the EASM domain. In this paper, a marsh depression on the central island was selected to reconstruct the locally hydrological variation and to discuss its indications for the Holocene EASM evolution. This work is based on multi-proxy (magnetic susceptibility, grain size, loss-on-ignition, and carbonate content) analyses of 22 modern sedimentary samples with a water-level gradient of 0–66 cm and 100 cored sedimentary samples covering last ~ 9.0 ka BP. The proxies’ hydrological significance was previously interpreted by the 22 modern samples using linear regression equations to construct their relationships to water-level changes. Among these proxies, the magnetic susceptibility, carbonate content, as well as the Md and sand fraction of grain size exhibit high-level relationships against the water-level changes with R2 > 0.6. Thus, these four proxies’ linear-regression equations were selected and used on the 100 cored samples, and the Holocene water-level changes in the studied depression were quantitatively reconstructed. It shows that two relatively high water-level stages with strengthened EASM occurred during 8.0–4.5 ka BP and 3.0–1.4 ka BP, which were alternated by three low water-level stages with declined EASM during ~ 9.0–8.0 ka BP, 4.5–3.0 ka BP, and 1.4–0 ka BP, respectively. Among these fluctuations, the highest water-level stage with most strengthened EASM which is defined as the Holocene Monsoon Maximum occurred during 6.4–4.5 ka BP. Such a new evolution pattern of the EASM can be further supported by a large variety of records from monsoon-margin regions. We suggest the Holocene EASM evolution was generally associated with the thermal conditions in both the inner Eurasia landmass and the West Pacific Ocean, with an exception of the weak EASM before 8.0 ka BP due to the enhanced Siberia High with the dominance of the Eurasia ice sheet in the early Holocene.

Evidence for the diet and habitat of two late Pleistocene mastodons from the Midwest, USA

AbstractWe analyzed intestinal contents of two late-glacial mastodons preserved in lake sediments in Ohio (Burning Tree mastodon) and Michigan (Heisler mastodon). A multi-proxy suite of macrofossils and microfossils provided unique insights into what these individuals had eaten just before they died and added significantly to knowledge of mastodon diets. We reconstructed the mastodons’ habitats with similar multi-proxy analyses of the embedding lake sediments. Non-pollen palynomorphs, especially spores of coprophilous fungi differentiated intestinal and environmental samples. The Burning Tree mastodon gut sample originates from the small intestine. The Heisler mastodon sample is part of the large intestine to which humans had added clastic material to anchor parts of the carcass under water to cache the meat. Both carcasses had been dismembered, suggesting that the mastodons had been hunted or scavenged, in line with other contemporaneous mastodon finds and the timing of early human incursion into the Midwest. Both mastodons lived in mixed coniferous-deciduous late-glacial forests. They browsed tree leaves and twigs, especiallyPicea. They also ate sedge-swamp plants and drank the lake water. Our multi-proxy estimates for a spring/summer season of death contrast with autumn estimates derived from prior tusk analyses. We document the recovered fossil remains with photographs.

Legacy of early anthropogenic effects on recent lake eutrophication (Lake Bénit, northern French Alps)

Abstract Mountain lakes are integrated sentinels of changes in the terrestrial environment, where these changes threaten the quality of the ecosystem services these lakes provide, including high biodiversity, economic and leisure activities. Few evidentiary records exist of the long-term relationships between human pressure and observed impacts. Multiproxy analyses of the Lake Benit sediment sequence, including dating, grain-size, geochemistry, pollen, non-pollen palynomorphs and chironomid assemblage reconstructions, allowed reconstruction of past environmental evolution and lake trophic changes. Combined with soil analyses of the catchment, these data provide a record of the relationships between human activities and the lake-catchment ecosystem, and show the effect of inundation of the shore previously used as pasture. From 2100 to 1100 yrs cal. BP, the catchment was forested. During the Middle Ages, grazing deforested the catchment, triggering an increase in erosion and a change in sediment sources. The lake remained oligotrophic over most of the last millennia. The trophic state changed abruptly in the 20th century with intensification and multiplication of tourist activities in the catchment, i.e., fishing, hiking, while pastoral activities decreased. The sudden eutrophication coincides with an artificial increase of the lake water level in AD 1964 to improve fishing activities. A release of phosphorus (P) from the flooded soils was observed, which may be responsible for the current eutrophication. One thousand years of grazing practices would have led to the observed P concentrations in the soils of the lake shore, transferred by the cattle to this area. Our study highlights the combined effects of past and recent activities on the current eutrophication process, and the legacy of both soils and early anthropogenic activities.

Deciphering Neolithic activities from a Cardial burial site (Cova Bonica) on the western Mediterranean coast

Cova Bonica has yielded one of the few assemblages of Cardial Neolithic records of directly dated human remains (c. 5470 and 5220 years cal. BC – unmodelled) in the Iberian Peninsula and has provided the first complete genome of an Iberian farmer. A minimum of seven individuals and six age clusters have been ascribed on the basis of the disarticulated human bones. A large number of archaeological artifacts have likewise been identified in the same layer, preserved in a small number of remnants in different areas of the cave. This study presents the results of a multi-proxy archaeological analysis of the spatial distribution, human remains, small and large mammals, palaeobotanical remains, lithics, ceramics and radiocarbon dating, with the aim of reconstructing the cave's history and the context of the layer containing the human remains. The results suggest the cave was used for at least two distinct purposes: one related to its use for funerary practices, as documented by a small group of artifacts (ornamental objects, ceramics, tools), charcoal and small mammals; the other related to its use as a sheep pen as indicated by reworked fumier, the results of a zooarchaeological study and an ovicaprine palaeodemographic profile. The paper concludes that the funerary and ritualistic practices of the Cardial Neolithic in SW Europe are difficult to reconstruct because human remains are often scattered in archaeological layers where other human activities may also have been conducted. For this reason, artifacts associated with human remains do not constitute a solid foundation on which to reconstruct funerary practices. Indeed, only a multi-proxy analysis of the archaeological material is capable of evaluating different geological and/or archaeological processes and their associated activities.

Correlating three centuries of historical and geological data for the marine deposit reconstruction of two depositional environments of the French Atlantic coast

This paper details a high-resolution record of French Atlantic coast extreme wave events using a multi-proxy analysis of dated sedimentary deposits. Two lagoons 1) the Petite Mer de Gâvres and 2) the Traicts du Croisic were chosen to identify damaging storm events from the last 300 years with Beeker sampling, 210Pb and 137Cs dating and sedimentary analysis. Using two new geochemical proxies in the French Atlantic coast, Sr/Fe and Ca/Ti, shows that several storminess events are reported in the nine cores drilled. By correlation with historical archives, seven major storms are confirmed: 1924 CE, 1940 CE, 1972 CE, 1977 CE, 1990 CE, 1999 CE, and an 1896 CE highly damaging event. Four other XIXth and XVIIIth century extreme wave event correlations are also proposed from this multi-proxy analysis: 1775 CE, 1811 CE, 1838 CE and 1876 CE. Societal and natural impacts caused by these coastal floods are revealed using our dense and varied historical archives.