The thermoluminescence (TL) and optically stimulated luminescence (OSL) sensitivities of quartz grains from deserts and loess–red clay sequences are used to trace eolian provenances in northern China. Our results indicate that the 110°C TL peak and OSL sensitivities of quartz grains show differences among Chinese deserts, which can be subdivided into four groups according to the spatial variations of luminescence sensitivities. Such differences are related mostly to the regional difference in rock types of mountains surrounding or adjacent to the deserts. We also examine the possible provenance changes between the Quaternary loess and the Tertiary eolian red clay, and the results indicate that the luminescence sensitivity of Tertiary red clay is higher than that of Quaternary loess (L1, L15, and L33), implying source materials of the eolian deposits changed relative to those of the Quaternary.

Two interstadial tree ring-width chronologies from Geikie Inlet, Glacier Bay Southeast, Alaska were built from 40 logs. One of these chronologies has been calendar dated to AD 224–999 (775 yr) crossdating with a living ring-width chronology from Prince William Sound, Alaska. Trees in this chronology were likely killed through inundation by sediments and meltwater from the advancing Geikie Glacier and its tributaries ca. AD 850. The earlier tree-ring chronology spans 545 yr and is a floating ring-width series tied to radiocarbon ages of about 3000 cal yr BP. This tree-ring work indicates two intervals of glacial expansion by the Geikie Glacier system toward the main trunk glacier in Glacier Bay between 3400 and 3000 cal yr BP and again about AD 850. The timing of both expansions is consistent with patterns of ice advance at tidewater glaciers in other parts of Alaska and British Columbia about the same time, and with a relative sea-level history from just outside Glacier Bay in Icy Strait. This emerging tree-ring dated history builds on previous radiocarbon-based glacial histories and is the first study to use tree-ring dating to assign calendar dates to glacial activity for Glacier Bay.

The analysis of macroscopic wood charcoal fragments extracted from soils is frequently used as a palaeoecological tool for reconstructing stand-scale forest composition and fire history. Here we explored the putative loss of palaeoecological information due to charcoal degradation through time and in different biogeographical settings. We compared the relationship between charcoal mass and abundance for soil samples from five biogeographical regions of boreal northeastern North America spanning most of the Holocene period. We verified whether charcoal (Ø ≥ 2 mm) conservation differed as a consequence of different taphonomical processes between organic and mineral soil types. We also assessed the mass/abundance relationship as a function of charcoal residence time in soil. Overall, the slope of the regression between charcoal particles mass (g) and abundance (number of particles) was 0.0042. The slope was not significantly different in samples from organic and mineral soil, and all biogeographical regions had similar slope values except one (higher charcoal fragmentation, probably due to high colluvial activity). Charcoal conservation also did not vary according to residence time in soil. This study shows that macroscopic soil charcoal particles resist fragmentation over millennia in different biogeographical settings and under the influence of various taphonomical processes.

Discovery of the Monte Verde archeological site in Chile overturned the previous consensus that the first Americans into the New World from Asia were the makers of Clovis projectile points, and rejuvenated the hypothesis that migration through the Americas occurred largely on portions of the Pacific continental shelf exposed by Pleistocene drawdown in eustatic sea level. The postulate of travel along a paleoshoreline now hidden underwater is an attractive means to posit pre-Clovis human movement southward from Beringia to Chile without leaving traces of migration onshore. Geologic analyses of the Pleistocene paleoenvironment at Monte Verde and of the morphology of the potential migration route along the continental shelf raise questions that have not been fully addressed. The periglacial setting of Monte Verde may call its antiquity into question and the narrowness of the Pacific continental shelf of the Americas makes it unlikely that people could travel the length of the Americas without impacting ground still onshore and no farther inland than Monte Verde itself. Geological perspectives on Monte Verde and coastal migration jointly suggest that the Clovis-first hypothesis for peopling the New World may have been abandoned prematurely.

In this study we compare the foraminifera of modern South San Francisco Bay with fossils from sediments of a previous estuary at 125 ka to provide a basis for interpreting the impact of natural and human change on the benthic ecosystem. All the species found in the Pleistocene sediments of this study are estuarine and/or shallow-water species occurring commonly in San Francisco Bay today, except for the introduced foraminifer Trochammina hadai, a native of Japan that was not found in samples taken in San Francisco Bay before 1983. The biodiversity and species composition of the fossil and modern assemblages before the introduction of T. hadai are nearly identical, suggesting that the environmental and physical changes in the 125,000-year-old and modern estuaries have not had a significant effect on the meiofauna of the Bay. In contrast, modern anthropogenic change in the form of species introductions has impacted the modern foraminiferal assemblage: T. hadai began to dominate the modern assemblage a decade after its introduction. Similar to the recorded impacts of introductions of marine metazoan invertebrate species, the dominance of T. hadai changed species proportions in the post-1980s foraminiferal assemblage, however no known extinctions in the native foraminiferal fauna occurred.

This study examines a sediment core (SR-63) from a mangrove ecosystem along the Sibun River in Belize, which is subject to both changes in sea-level and in the characteristics of the river's drainage basin. Radiocarbon dates from the core show a decreased sedimentation rate from ~ 6 ka to 1 cal ka BP and a marked change in lithology from primarily mangrove peat to fluvial-derived material at ~ 2.5 cal ka BP. Changes in the sedimentation rates observed in mangrove ecosystems offshore have previously been attributed to changes in relative sea-level and the rate of sea-level rise. Pollen analyses show a decreased abundance of Rhizophora (red mangrove) pollen and an increased abundance of Avicennia (black mangrove) pollen and non-mangrove pollen coeval with the decreased sedimentation rates. Elemental ratios ([N:C]a) and stable isotope analyses (δ15N and δ13C) show that changes in the composition of the organic material are also coeval with the change in lithology. The decrease in sedimentation rate at the site of core SR-63 and at offshore sites supports the idea that regional changes in hydrology occurred during the Holocene in Belize, influencing both mainland and offshore mangrove ecosystems.

Multiproxy analysis of three littoral cores from western New Caledonia supports the hypothesis that the main controlling factors of environmental changes are sea-level change, ENSO variability and extra-tropical phenomena, such as the Medieval Warm Period (MWP) marked by a tendency for La Niña-like conditions in the tropical Pacific. The record starts during the late Holocene sea-level rise when the terrestrial vegetation indicated wet and cool conditions. The site was a coastal bay definitely transformed into a freshwater swamp at around 3400 cal yr BP, after the rapid drawdown of sea level to its current level. Sediments and foraminiferal assemblages indicated subsequent episodes of freshwater infillings, emersion or very high-energy conditions, likely related to climatic changes and mostly controlled by ENSO variability. Between 2750 and 2000 cal yr BP, relatively dry and cool climate prevailed, while wetter conditions predominated between ca. 1800 and 900 cal yr BP. The Rhizophoraceae peak between ca. 1080 and 750 cal yr BP, coeval with the MWP, may indicate a global phenomenon. Microcharcoal particles present throughout the record increased after 1500 cal yr BP, suggesting an anthropogenic source. From ca. 750 cal yr BP the appearance of current type of vegetation marks the human impact.

Arid and Alpine ecosystems are known for extreme environmental changes during the Late Quaternary. We hypothesize that the world's largest Alpine arid ecosystem however, the Alpine Steppes of the Tibetan highlands, remained ecologically stable during the LGM and the mid-Holocene. This hypothesis is tested by distributional range of plant species, plant life forms and rate of endemism. The set of character species has a precipitation gradient between 50 and 350 mm/a, testifying for resilience to precipitation changes. 83% of the species have a wider vertical range than 1000 m used as a proxy for resilience to temperature changes. 30% of the species are endemic with 10 endemic genera, including plate-shaped cushions as a unique plant life form. These findings are in line with palaeo-ecological proxies (δ18O, pollen) allowing the assumption that Alpine Steppes persisted during the LGM with 3 to 4 K lower summer temperatures.

During the mid-Holocene, forests could have replaced Alpine Steppes in the upper catchments of the Huang He, Yangtze, Mekong, Salween and Yarlung Zhangbo, but not in the interior basins of the north-western highlands, because the basins were then flooded, suppressing forests and supporting the environmental stability of this arid Alpine grassland biome.

The Andean piedmont of Mendoza is a semiarid region covered by extensive and partially vegetated dune fields consisting of mostly inactive aeolian landforms of diverse size and morphology. This paper is focused on the San Rafael plain (SRP) environment, situated in the distal Andean piedmont of Mendoza (34° 30′S), and reports the sedimentology and OSL chronology of two representative exposures of late Quaternary deposits, including their paleoenvironmental and paleoclimatic significance. Eleven facies, including channel, floodplain, fluvio–aeolian interaction, and reworked pyroclastic and aeolian deposits, were described and grouped into two facies associations (FA1 and FA2). FA1 was formed by unconfined sheet flows, minor channelized streams and fluvial–aeolian interaction processes. FA2 was interpreted as aeolian dune and sand-sheet deposits. OSL chronology from the SRP sedimentary record indicates that between ca. 58–39 ka and ca. 36–24 ka (MIS 3), aggradation was governed by ephemeral fluvial processes (FA1) under generally semiarid conditions. During MIS 2, the last glacial maximum (ca. 24–12 ka), a major climatic shift to more arid conditions is documented by significant aeolian activity (FA2) that became the dominant sedimentation process north of the Diamante–Atuel fluvial system. The inferred paleoenvironmental conditions from the SRP sections are in broad agreement with regional evidence.

The type section silts of the late Pleistocene Wilson Creek Formation at Mono Lake contain outsized clasts, dominantly well-rounded pebbles and cobbles of Sierran lithologies. Lithic grains > 425 μm show a similar pattern of variability as the > 10 mm clasts visible in the type section, with decreasing absolute abundance in southern and eastern outcrops. The largest concentrations of ice-rafted debris (IRD) occur at 67–57 ka and 46–32 ka, with strong millennial-scale variability, while little IRD is found during the last glacial maximum and deglaciation.

Stratigraphic evidence for high lake level during high IRD intervals, and a lack of geomorphic evidence for coincidence of lake and glaciers, strongly suggests that rafting was by shore ice rather than icebergs. Correspondence of carbonate flux and IRD implies that both were mainly controlled by freshwater input, rather than disparate non-climatic controls. Conversely, the lack of IRD during the last glacial maximum and deglacial highstands may relate to secondary controls such as perennial ice cover or sediment supply. High IRD at Mono Lake corresponds to low glacial flour flux in Owens Lake, both correlative to high warm-season insolation. High-resolution, extra-basinal correlation of the millennial peaks awaits greatly improved age models for both records.

Understanding the timing of mountain glacier and paleolake expansion and retraction in the Great Basin region of the western United States has important implications for regional-scale climate change during the last Pleistocene glaciation. The relative timing of mountain glacier maxima and the well-studied Lake Bonneville highstand has been unclear, however, owing to poor chronological limits on glacial deposits. Here, this problem is addressed by applying terrestrial cosmogenic 10Be exposure dating to a classic set of terminal moraines in Little Cottonwood and American Fork Canyons in the western Wasatch Mountains. The exposure ages indicate that the main phase of deglaciation began at 15.7 ± 1.3 ka in both canyons. This update to the glacial chronology of the western Wasatch Mountains can be reconciled with previous stratigraphic observations of glacial and paleolake deposits in this area, and indicates that the start of deglaciation occurred during or at the end of the Lake Bonneville hydrologic maximum. The glacial chronology reported here is consistent with the growing body of data suggesting that mountain glaciers in the western U.S. began retreating as many as 4 ka after the start of northern hemisphere deglaciation (at ca. 19 ka).

Previous studies have suggested that Marine Isotope Stage (MIS) 13, recognized as atypical in many paleoclimate records, is marked by the development of anomalously strong summer monsoons in the northern tropical areas. To test this hypothesis, we performed a multi-proxy study on three marine records from the tropical Indian Ocean in order to reconstruct and analyse changes in the summer Indian monsoon winds and precipitations during MIS 13. Our data confirm the existence of a low-salinity event during MIS 13 in the equatorial Indian Ocean but we argue that this event should not be considered as “atypical”. Taking only into account a smaller precession does not make it possible to explain such precipitation episode. However, when considering also the larger obliquity in a more complete orbitally driven monsoon “model,” one can successfully explain this event. In addition, our data suggest that intense summer monsoon winds, although not atypical in strength, prevailed during MIS 13 in the western Arabian Sea. These strong monsoon winds, transporting important moisture, together with the effect of insolation and Eurasian ice sheet, are likely one of the factors responsible for the intense monsoon precipitation signal recorded in China loess, as suggested by model simulations.