Late Pleistocene and Holocene Afromontane vegetation and headwater wetland dynamics within the Eastern Mau Forest,Kenya

The Mau Forest Complex is Kenya's largest fragment of Afromontane forest, providing critical ecosystem services, and has been subject to intense land use changes since colonial times. It forms the upper catchment of rivers that drain into major drainage networks, thus supporting the livelihoods of millions of Kenyans and providing important wildlife areas. We present the results of a sedimentological and palynological analysis of a Late Pleistocene–Holocene sediment record of Afromontane forest change from Nyabuiyabui wetland in the Eastern Mau Forest, a highland region that has received limited geological characterization and palaeoecological study. Sedimentology, pollen, charcoal, X-ray fluorescence and radiocarbon data record environmental and ecosystem change over the last ~16 000 cal a bp. The pollen record suggests Afromontane forests characterized the end of the Late Pleistocene to the Holocene with dominant taxa changing from Apodytes, Celtis, Dracaena, Hagenia and Podocarpus to Cordia, Croton, Ficus, Juniperus and Olea. The Late Holocene is characterized by a more open Afromontane forest with increased grass and herbaceous cover. Continuous Poaceae, Cyperaceae and Juncaceae vegetation currently cover the wetland and the water level has been decreasing over the recent past. Intensive agroforestry since the 1920s has reduced Afromontane forest cover as introduced taxa have increased (Pinus, Cupressus and Eucalyptus).     

Multi-proxy reconstruction of the Holocene vegetation and land use dynamics in the Julian Alps,north-west Slovenia

Small mountain lakes are natural archives for understanding long-term natural and anthropogenic impact on the environment. This study focused on long-term (last ca. 13 000 years) vegetation changes and sedimentary processes in the catchment area of Lake Planina pri jezeru (1430 m a.s.l.) by using mineralogical, geochemical and palynological methods. Palynological results suggest that regional vegetation between 12 900 and 11 700 cal a bp was a herbaceous–forest tundra (Pinus, Artemisia, Poaceae ). Climate warming at the beginning of the Holocene (ca. 11 700 cal a bp ) caused the transition from a wetland (Cyperaceae) to an eutrophic lake with alternating anoxic (pyrite) and oxic conditions (gypsum). In addition, the surrounding area became forested (Picea, Larix, Ulmus). Fagus expanded at 10 200 cal a bp and Abies at 8200 cal a bp. Between 7500 and 4300 cal a bp , human impact on the environment was barely noticeable and mostly limited to grazing. During 4300–430 cal a bp human impact became more evident and gradually increased. The greatest influence was observed from 430 cal a bp onwards, when excessive exploitation of the surrounding area (logging and grazing) severely eutrophicated the lake.     

Lacustrine sedimentation in active volcanic settings: the Late Quaternary depositional evolution of Lake Chungará (northern Chile)

Lake Chungará (18°15′S, 69°09′W, 4520 m above sea‐level) is the largest (22·5 km²) and deepest (40 m) lacustrine ecosystem in the Chilean Altiplano and its location in an active volcanic setting, provides an opportunity to evaluate environmental (volcanic vs. climatic) controls on lacustrine sedimentation. The Late Quaternary depositional history of the lake is reconstructed by means of a multiproxy study of 15 Kullenberg cores and seismic data. The chronological framework is supported by 10 ¹⁴C AMS dates and one ²³⁰Th/²³⁴U dates. Lake Chungará was formed prior to 12·8 cal kyr bp as a result of the partial collapse of the Parinacota volcano that impounded the Lauca river. The sedimentary architecture of the lacustrine succession has been controlled by (i) the strong inherited palaeo‐relief and (ii) changes in the accommodation space, caused by lake‐level fluctuations and tectonic subsidence. The first factor determined the location of the depocentre in the NW of the central plain. The second factor caused the area of deposition to extend towards the eastern and southern basin margins with accumulation of high‐stand sediments on the elevated marginal platforms. Synsedimentary normal faulting also increased accommodation and increased the rate of sedimentation in the northern part of the basin. Six sedimentary units were identified and correlated in the basin mainly using tephra keybeds. Unit 1 (Late Pleistocene–Early Holocene) is made up of laminated diatomite with some carbonate‐rich (calcite and aragonite) laminae. Unit 2 (Mid‐Holocene–Recent) is composed of massive to bedded diatomite with abundant tephra (lapilli and ash) layers. Some carbonate‐rich layers (calcite and aragonite) occur. Unit 3 consists of macrophyte‐rich diatomite deposited in nearshore environments. Unit 4 is composed of littoral sediments dominated by alternating charophyte‐rich and other aquatic macrophyte‐rich facies. Littoral carbonate productivity peaked when suitable shallow platforms were available for charophyte colonization. Clastic deposits in the lake are restricted to lake margins (Units 5 and 6). Diatom productivity peaked during a lowstand period (Unit 1 and subunit 2a), and was probably favoured by photic conditions affecting larger areas of the lake bottom. Offshore carbonate precipitation reached its maximum during the Early to Mid‐Holocene (ca 7·8 and 6·4 cal kyr bp ). This may have been favoured by increases in lake solute concentrations resulting from evaporation and calcium input because of the compositional changes in pyroclastic supply. Diatom and pollen data from offshore cores suggest a number of lake‐level fluctuations: a Late Pleistocene deepening episode (ca 12·6 cal kyr BP), four shallowing episodes during the Early to Mid‐Holocene (ca 10·5, 9·8, 7·8 and 6·7 cal kyr BP) and higher lake levels since the Mid‐Holocene (ca 5·7 cal kyr BP) until the present. Explosive activity at Parinacota volcano was very limited between c. >12·8 and 7·8 cal kyr bp . Mafic‐rich explosive eruptions from the Ajata satellite cones increased after ca 5·7 cal kyr bp until the present.     

A first Holocene leaf wax isotope-based paleoclimate record from the semi-humid to semi-arid south-eastern Caucasian lowlands

The Holocene paleoclimate of the Caucasus region is rather complex and not yet well understood: while existing studies are mainly based on pollen records from high-altitude and humid lowland regions, no records are available from the semi-humid to semi-arid south-eastern Caucasian lowlands. Therefore, this study investigated compound-specific δ²H and δ¹³C isotopes of leaf wax biomarkers from Holocene floodplain soils in eastern Georgia. Our results show that the leaf wax δ²H signal from the paleosols mostly reflects changes in the moisture source and its isotopic composition. Depleted δ²H values before ~8 cal ka bp change towards enriched values after ~5 cal ka bp and become again depleted after ~1.6 cal ka bp. This trend could be caused by Holocene changes of the isotopic compositions of the Black and eastern Mediterranean Sea, and/or by varying contribution of both moisture sources linked with the North Atlantic Oscillation. The leaf wax δ¹³C signal from the paleosols directly indicates varying local water availability and drought stress. Depleted δ¹³C values before ~8 and after ~5 cal ka bp indicate wetter local conditions with higher water availability, whereas more enriched values during the middle Holocene (~8 until at least 5 cal ka bp ) indicate drier conditions with increased drought stress.     

Holocene survival of the wild horse in Europe: a matter of open landscape?

The wild horse Equus ferus was one of the most frequent species of the Late Pleistocene large ungulate fauna in Eurasia and played an important role in the subsistence of human groups, especially at the end the Late Glacial. It is frequently assumed that E. ferus became extinct in Europe at the beginning of the Holocene because of the development of woodlands and loss of open habitats. Because of its preference for open habitats and in spite of its adaptability, the appearance or disappearance of the wild horse could therefore be a suitable palaeoecological indicator for the opening of the Holocene primeval woodlands. We revised the dating and reliability of the subfossil record and dated several bones by atomic mass spectrometry ¹⁴C dating. From the beginning of the Holocene (9600 cal a BC) to the end of the Atlantic Period (3750 cal a BC) there are 207 archaeological sites with wild horse records available in Europe. E. ferus survived the Pleistocene Holocene transition in Europe, but the spatiotemporal dynamics of populations fluctuated remarkably in the early and middle Holocene. Small and sparse populations increasingly became extinct during the early Holocene, until between 7100 and 5500 cal a BC the wild horse was almost absent in central parts of the European Lowlands. Particular conditions in natural open patches in the canopy forests, chalklands and floodplains may have maintained the local survival of the horse in some regions of the Lowlands, however. In the Late Atlantic, between 5500 and 3750 cal a BC the range of the wild horse was again extended. It re‐immigrated into central and western Europe, probably as a consequence of increasing landscape opening by Neolithic peoples. The data presented here may be a valuable part of the debate on the degree of openness of the early and middle Holocene landscape. Copyright © 2011 John Wiley & Sons, Ltd.     

Holocene coastal change at Luce Bay,South West Scotland

Coastal change during the Mid- to Late Holocene at Luce Bay, South West Scotland, is examined using morphological, stratigraphic and biostratigraphical techniques supported by radiocarbon dating. Deglaciation left extensive sediments, providing a source for depositional coastal landforms. Glacio-isostatic uplift resulted in the registration of evidence for former relative sea levels (RSLs), which support the pattern of Holocene RSL change for the northern Irish Sea as determined by shoreline-based Gaussian trend surface models. The rate of RSL rise was rapid from before ca. 8600 to ca. 7800 cal a bp , but then slowed, changing by <3 m over the next 3000 years, a pattern reflected in the convergence of shorelines predicted in the models. By ca. 4400 cal a bp RSL was falling towards present levels. As these changes were taking place, coastal barriers developed and dunes formed across them. In the West of the Bay, a lagoon forming to landward of the barriers and dunes acted as a sediment sink for dune sand. Changes in the coastal landscape influenced the occupation of the area by early human societies. This study illustrates the value of combining an understanding of process geomorphology, RSL and archaeology in studies of coastal change.     

Late Quaternary glacier and sea-ice history of northern Wijdefjorden,Svalbard

The deglaciation history and Holocene environmental evolution of northern Wijdefjorden, Svalbard, are reconstructed using sediment cores and acoustic data (multibeam swath bathymetry and sub-bottom profiler data). Results reveal that the fjord mouth was deglaciated prior to 14.5±0.3 cal. ka BP and deglaciation occurred stepwise. Biomarker analyses show rapid variations in water temperature and sea ice cover during the deglaciation, and cold conditions during the Younger Dryas, followed by minimum sea ice cover throughout the Early Holocene, until c. 7 cal. ka BP. Most of the glaciers in Wijdefjorden had retreated onto land by c. 7.6±0.2 cal. ka BP. Subsequently, the sea-ice extent increased and remained high throughout the last part of the Holocene. We interpret a high Late Holocene sediment accumulation rate in the northernmost core to reflect increased sediment flux to the site from the outlet of the adjacent lake Femmilsjøen, related to glacier growth in the Femmilsjøen catchment area. Furthermore, increased sea ice cover, lower water temperatures and the re-occurrence of ice-rafted debris indicate increased local glacier activity and overall cooler conditions in Wijdefjorden after c. 0.5 cal. ka BP. We summarize our findings in a conceptual model for the depositional environment in northern Wijdefjorden from the Late Weichselian until present.     

A Holocene high-resolution record of aquatic productivity,seasonal anoxia and meromixis from varved sediments of Lake Łazduny,North-Eastern Poland: insight from a novel multi-proxy approach

Anthropogenic eutrophication and spreading anoxia in freshwater systems is a global concern. Little is known about anoxia in earlier historic times under weaker human impact, or under prehistoric natural conditions with different trophic, land cover and climatic regimes. We use a novel approach that combines high-resolution hyperspectral imaging with µ-XRF and HPLC-pigment data, which allows us to assess chloropigments (productivity) and bacteriopigments (anoxia) at seasonal subvarve-scale resolution. Our ~9700 cal a bp varved sediment record from NE Poland suggests that productivity increased stepwise from oligotrophic Early Holocene conditions (until ~9200 cal a bp ) to mesotrophic conditions in the Mid- and Late Holocene. Natural eutrophication was mainly a function of progressing landscape evolution with intense weathering under dense forest and warm-moist climatic conditions. Generally, anoxia increased with increasing productivity. Seasonal anoxia and some multi-decadal periods of meromixis were the common mixing patterns throughout the Holocene except for a period of persisting meromixis between ~5200 and 2000 cal a bp. Anthropogenic deforestation around 400 cal a bp resulted in substantially better lake oxygenation despite high productivity. In this small lake, aquatic productivity and lakeshore forest cover (wind shield) were more important factors controlling oxic/anoxic conditions than Holocene temperature variability.     

Late glacial and Holocene landscape change and rapid climate and coastal impacts in the Canal Beagle,southernmost Patagonia

Palaeoenvironmental data for the Late Glacial and Holocene periods are provided from Caleta Eugenia, in the eastern sector of Canal Beagle, southernmost Patagonia. The record commences at c. 16 200 cal a bp following glacier retreat in response to climatic warming. However, cooler conditions persisted during the Late Glacial period. The onset of more temperate conditions after c. 12 390 cal a bp is indicated by the arrival of southern beech forest and later establishment at c. 10 640 cal a bp , but the woodland growth was restricted by lower levels of effective moisture. The climate signal is then truncated by a rapid marine incursion at c. 8640 cal a bp which lasted until a more gradual emergence of the coast at c. 6600 cal a bp. During this period the pollen record appears to be dominated by the southern beech woodland. A punctuated hydroseral succession follows the isolation of the site from the sea leading to the re‐establishment of a peat bog. Between c. 5770 cal a bp and the present there were several periods of short rapid climatic change leading to drier conditions, probably as a result of late Holocene periods of climatic warming. Copyright © 2019 John Wiley & Sons, Ltd.     

Holocene vegetation history in Romanian Subcarpathians

Pollen analysis from a peat core 7.0 m in length, taken from a bog near Bisoca, in a mid-altitude area of the Buzăului Subcarpathian mountains, is used to reconstruct the postglacial vegetation history of the region. The vegetation record, which is supported by twelve ¹⁴C dates, starts at the end of the Late Glacial period. At the Late Glacial/Holocene transition, open vegetation was replaced by forest, suggesting a fast response to climatic warming. The Holocene began with the expansion of Betula, Pinus and Ulmus, followed, after 11,000 cal yr BP, by Fraxinus, Quercus, Tilia and Picea. The rapid expansion of these taxa may be due to their existence in the area during the Late Glacial period. At ca. 9200 cal yr BP, Corylus expanded, reaching a maximum after 7600 cal yr BP. The establishment of Carpinus occurred at ca. 7200 cal yr BP, with a maximum at ca. 5700 cal yr BP. Fagus pollen is regularly recorded after 7800 cal yr BP and became dominant at ca. 2000 cal yr BP. The first indications of human activities appear around 3800 cal yr BP.     

Late Glacial and Holocene vegetation history in the southern part of Transylvania (Romania): pollen analysis of two sequences from Avrig

We present here the results of pollen analysis of two sequences of about 8.06 m and 11.90 m length, originating from two adjacent peat bogs in the southern part of Transylvania province, Romania (155 and 122 pollen spectra). The vegetation record, which is supported by 17 ¹⁴C dates, begins in the Late Glacial interstadial when forest recolonisation began with the development of Pinus, without a pioneer Betula phase. Picea began to expand from regional refuges. After a well‐defined Younger Dryas, the Holocene opens with the expansion of Betula, Ulmus and Picea, followed, at about 10 400 cal. yr BP, by Fraxinus, Quercus and Tilia. The Corylus optimum is correlated with the Atlantic chronozone (after 8600 cal. yr BP). The local establishment of Carpinus occurred at about 6500 cal. yr BP, with a maximum at about 5700 cal. yr BP. Fagus pollen is regularly recorded after 8200 cal. yr BP. This taxon became dominant at about 3700 cal. yr BP. The first indications of human activities appear at around 7200 cal. yr BP. Copyright © 2005 John Wiley & Sons, Ltd.     

Reconstruction of the Late Holocene climate and environmental history from North Bolgoda Lake,Sri Lanka,using lipid biomarkers and pollen records

The catastrophic impact and unpredictability of the Indian Ocean Monsoon (IOM) over South Asia are evident from devastating floods, mudslides and droughts in one of the most densely populated regions of the globe. However, our understanding as to how the IOM has varied in the past, as well as its impact on local environments, remains limited. This is particularly the case for Sri Lanka, where erosional landscapes have limited the availability of well-stratified, high-resolution terrestrial archives. Here, we present novel data from an undisturbed sediment core retrieved from the coastal Bolgoda Lake. This includes the presentation of a revised Late Holocene age model as well as an innovative combination of pollen, source-specific biomarkers, and compound-specific stable carbon isotopes of n-alkanes to reconstruct the shifts in precipitation, salinity and vegetation cover. Our record documents variable climate between 3000 years and the present, with arid conditions c. 2334 and 2067 cal a bp. This extreme dry period was preceded and followed by more wet conditions. The high-resolution palaeoenvironmental reconstruction fills a major gap in our knowledge on the ramifications of IOM shifts across South Asia and provides insights during a time of major redistribution of dense human settlements across Sri Lanka.     

Effects of the middle Holocene high sea-level stand and climate on Amazonian mangroves

The high sea-level stand during the mid-Holocene is a benchmark in mangrove dynamics along the north-east/south-east coast of Brazil and provides a reference point for landward and seaward mangrove migrations corresponding to changes in relative sea level (RSL). However, evidence of the impacts associated with RSL fall on the northern Brazilian coast is scarce. Multi-proxy data from the highest tidal flats of the Bragança Peninsula in northern Brazil revealed modern herbaceous areas were occupied by mangroves Rhizophora and Avicennia from ~6250 to ~5850 cal a bp , and only Avicennia between ~5850 and ~5000 cal a bp . The same tidal flats were vegetation-free between ~5000 and ~4300 cal a bp . A combination of a high sea-level stand (0.6 ± 0.1 m) at ~5000 cal a bp and a dry early–middle Holocene in the Amazon probably caused an increase in porewater salinity of tidal flats, which resulted in a mangrove succession from Rhizophora to Avicennia dominance. RSL fall accentuated this process, contributing to mangrove degradation between ~5000 and ~4300 cal a bp . RSL fall, and a wetter period over the past ~4300 cal a bp caused a mangrove migration from highest to lowest flats, followed by expansion of herbaceous vegetation on the highest flats.     

Paleoecological and climatic changes of the Upper Lerma Basin, Central Mexico during the Holocene

The record of Almoloya Lake in the Upper Lerma basin starts with the deposition of the late Pleistocene Upper Toluca Pumice layer. The data from this interval indicate a period of climatic instability that lasted until 8500 cal yr B.P., when temperature conditions stabilized, although moisture fluctuations continued until 8000 cal yr B.P. Between 8500 and 5000 cal yr B.P. a temperate climate is indicated by dominance of Pinus. From 5000 to 3000 cal yr B.P. Quercus forest expanded, suggesting a warm temperate climate: a first indication of drier environmental conditions is an increase in grassland between 4200 and 3500 cal yr B.P. During the Late Holocene (3300 to 500 cal yr B.P.) the increase of Pinus and grassland indicates temperate dry conditions, with a considerable increase of Pinus between 1100 and 950 cal yr B.P. At the end of this period, humidity increased. The main tendency during the Holocene was a change from humid to dry conditions. During the Early Holocene, Almoloya Lake was larger and deeper; the changing humidity regime resulted in a fragmented marshland, with the presence of aquatic and subaquatic vegetation types.     

Reconstruction of the Late Quaternary Glaciation of the Macha Khola valley (Gorkha Himal, Nepal) using relative and absolute (C, Be, dendrochronology) dating techniques

Late Quaternary glacier fluctuations in the Macha Khola valley (Gorkha Himal, Nepal) were reconstructed using relative and absolute dating techniques. Our results indicate that younger moraine complexes were left by Late Holocene (<1.7 cal. ka BP), mid-Holocene (ca 3 cal. ka BP), and Lateglacial (ca 13 cal. ka BP) ice advances. Older Late Quaternary glacier advances occurred during Marine Oxygen Isotope Stages (MIS) 2 and 3–4. No relics of Middle or Early Pleistocene glaciations could be found. During MIS 3–4, glaciers advanced down to an altitude of at least 2150 m a.s.l., corresponding to an ELA depression of approximately 1300 m. At about 3500 m a.s.l., the MIS 2 Macha Khola glacier reached almost the thickness of the former MIS 3–4 glacier and retreated some time before 17.9 cal. ka BP. The Lateglacial glacier advanced again several times to altitudes between 2450 and 3400 m a.s.l. The mid-Holocene glaciers extended much farther down-valley than the Late Holocene ones. Dendrochronological data of Abies spectabilis suggested several periods of unfavourable growth conditions especially at the beginning of the 19th (1820) and 20th (1905) centuries.     

Late Quaternary vegetation and climate dynamics in central-eastern Brazil: insights from a ~35k cal a bp peat record in the Cerrado biome

The late Quaternary evolution of central-eastern Brazil has been under-researched. Questions remain as to the origin of the Cerrado, a highly endangered biome, and other types of vegetation, such as the Capões – small vegetation islands of semi-deciduous and mountain forests. We investigated the factors that influenced the expansion and contraction of the Cerrado and Capões during the late Quaternary (last ~35 ka), using a multi-proxy approach: stable isotopes (δ¹³C, δ¹⁵N), geochemistry, pollen and multivariate statistics derived from a peat core (Pinheiro mire, Serra do Espinhaço Meridional). Five major shifts in precipitation, temperature, vegetation and landscape stability occurred at different timescales. Our study revealed that changes in the South Atlantic Convergence Zone (SACZ) seem to have been coeval with these shifts: from the Late Glacial Maximum to mid-Holocene the SACZ remained near (~29.6 to ~16.5k cal a bp ) and over (~16.5 to ~6.1 k cal a bp ) the study area, providing humidity to the region. This challenges previous research which suggested that climate was drier for this time period. At present, the Capões are likely to be a remnant of a more humid climate; meanwhile, the Cerrado biome seems to have stablished in the late Holocene, after ~3.1 k cal a bp .     

Holocene environmental and climatic changes inferred from Wulungu Lake in northern Xinjiang, China

Sedimentological, geochemical and palynological data from Wulungu Lake in northern Xinjiang, China, are used to reconstruct environmental and climate changes since 9550 cal yr BP. High abundance of Sparganium and Poaceae, low Md (median diameter) and δ¹³C_organic values indicate aridity between 9550 and 6730 cal yr BP. High Md and δ¹³C_organic values, and the prevalence of desert-steppe and steppe vegetation between 4200 and 560 cal yr BP, indicate that effective moisture increased after 6730 cal yr BP, peaking at 4200 and 560 cal yr BP. Low Md values, a negative excursion of δ¹³C_org, and the transition from steppe to desert vegetation since 560 cal yr BP reflect a decrease in effective moisture during the latest Holocene. Late Holocene human activities were indicated by sharp increase in the abundance of Pediastrum then. Variations in carbonate contents indicate that temperature was generally high between 9550 and 7740 cal yr BP, low between 7740 and 6730 cal yr BP, intermediate between 6730 and 560 cal yr BP, and low during the last 560 yr. Regional comparison indicates that the Asian monsoon did not extend to Wulungu Lake and westerlies were the main factor in determining the moisture availability during the Holocene.     

The Falkland Islands’ palaeoecological response to millennial‐scale climate perturbations during the Pleistocene–Holocene transition: Implications for future vegetation stability in the southern ocean islands

Oceanic island flora is vulnerable to future climate warming, which is likely to promote changes in vegetation composition, and invasion of non‐native species. Sub‐Antarctic islands are predicted to experience rapid warming during the next century; therefore, establishing trajectories of change in vegetation communities is essential for developing conservation strategies to preserve biological diversity. We present a Late‐glacial‐early Holocene (16 500–6450 cal a bp ) palaeoecological record from Hooker's Point, Falkland Islands (Islas Malvinas), South Atlantic. This period spans the Pleistocene‐Holocene transition, providing insight into biological responses to abrupt climate change. Pollen and plant macrofossil records appear insensitive to climatic cooling during the Late‐glacial, but undergo rapid turnover in response to regional warming. The absence of trees throughout the Late‐glacial‐early Holocene enables the recognition of far‐travelled pollen from southern South America. The first occurrence of Nothofagus (southern beech) may reflect changes in the strength and/or position of the Southern Westerly Wind Belt during the Late‐glacial period. Peat inception and accumulation at Hooker's Point is likely to be promoted by the recalcitrant litter of wind‐adapted flora. This recalcitrant litter helps to explain widespread peatland development in a comparatively dry environment, and suggests that wind‐adapted peatlands can remain carbon sinks even under low precipitation regimes. © 2019 The Authors. Journal of Quaternary Science Published by John Wiley & Sons Ltd.     

Consistent long-term Holocene warming trend at different elevations in the Altai Mountains in arid central Asia

Recent results indicate contrasting Holocene moisture histories at different elevations in arid central Asia (ACA). However, relatively little is known about Holocene temperature changes at different elevations. Here we report an independently dated peat brGDGTs-based MBT'_5ME record from the Narenxia peatland (NRX) in the southern Altai Mountains. The record suggests a long-term warming trend since ~7.7 cal. kyr bp , with a warmer stage during ~7–5.5 cal. kyr bp , a cold stage during ~5.5–4 cal. kyr bp , and a warming trend over the last ~4 kyr. The long-term warming trend indicated by the NRX MBT'_5ME record is largely consistent with Holocene temperature records from nearby sites covering an altitudinal range of ~1700–4100 m above sea level. This consistent long-term warming trend at different elevations differs from the long-term Holocene drying/wetting trends at high/low elevations of the Altai Mountains. We propose that the warming trend and consequent permafrost thawing at high elevations could have resulted in increased meltwater runoff, which would have contributed to the long-term wetting trend at low elevations. Our findings potentially provide an improved understanding of regional climate change and associated water resource availability, with implications for their possible future status.     

Changes in ostracod assemblages and morphologies during lake‐level variations of Lago Cardiel (49°S), Patagonia,Argentina, over the last 15.6 ka

Changes in the ostracod assemblages from two sediment cores collected from Lago Cardiel in southeastern Patagonia (49°S) reflect the main regional abrupt climatic changes over the last 15.6 cal. ka BP. Shifts in species abundance and switches in dominances suggest that these were mainly driven by variable salinity. During the Late Pleistocene, Limnocythere rionegroensis was abundant and dominant, indicating waters with high salinity and prevalence of evaporative processes. Between 12.6 and 10.8 cal. ka BP, Lago Cardiel expanded markedly and reached an Early Holocene highstand of +55 m above present lake level. A major change in ostracod assemblage in which Limnocythere patagonica appears as the dominant species in parallel with the disappearance of L. rionegroensis and Eucypris aff. cecryphalium mirrored this transitional period between the cold and dry Late Pleistocene and the humid and warm Early Holocene. Over the last 4 cal. ka BP, L. rionegroensis returned to the species assemblage and Riocypris whatleyi increased its abundance pointing towards increasing salinities. The variations in size, shape and ornamentation of L. rionegroensis and R. whatleyi fossil valves were examined using geometric morphometric techniques and further compared to those of modern Patagonian sites. Limnocythere rionegroensis specimens displayed high morphological variability during the evolution of Lago Cardiel. More specifically, the switch in reproductive mode – from sexual to parthenogenetic– and the increase in valve ornamentation around 12.7 cal. ka BP suggest that these changes were promoted by the hydrological alteration that occurred in the Late Pleistocene. This exercise provides a robust range of morphological variation for these proxies, which will be useful in further taxonomic and palaeoenvironmental studies adding more information about different factors influencing the observed morphological trends.