The age distribution of detrital zircon has been used to trace sediment sources. Existing datasets show great similarity of zircon ages between the loess on the Chinese Loess Plateau (CLP) and the sediments from the North Tibetan Plateau (NTP), implying that eolian dust is delivered from the NTP to the CLP by westerly winds or via the Yellow River. However, NTP dust can also be transported by northwesterly winds from the Alxa arid lands (AALs), where materials are received from both the NTP and the Gobi Altay Mountains (GAMs). Here we report U–Pb zircon ages for AALs sands and NTP and CLP loess. The results show that the zircons in the AALs are mixed from NTP and GAMs zircons. NTP loess is mainly derived from local sources. Mixing of materials from the NTP and GAMs defines the zircon ages of the loess on the CLP better than the pure NTP source. No temporal and spatial heterogeneities of zircon ages have been observed for the loess on the CLP, which suggests that the well-mixed materials in the AALs likely have an eolian source.

Manganese (Mn) in lake sediments reacts strongly to changes of redox conditions. This study analyzed Mn concentrations in oxides, carbonates, and bulk phases of the calcareous lacustrine sediments of a 938.5-m-long core (SG-1) taken from the western Qaidam Basin, well dated from 2.77 Ma to 0.1 Ma. Comparisons of extractions from diluted hydrochloric acid, acetic acid and citrate"bicarbonate"dithionite demonstrate that variations of Mn concentrations from acetic acid leaching (MnHOAc) are mostly responsible for Mn (II) fluctuations in the carbonate phase. Taking into account the relevant processes during weathering, transportation, deposition and post-deposition of Mn-bearing rocks, we conclude that Mn input from catchment weathering and paleolake redox condition provide the primary controls on variations in the Mn records of carbonate and oxide phases. We propose MnHOAc as a new sensitive indicator of paleolake redox evolution and catchment-scale climate change. The MnHOAc variations show a long-term upward decreasing trend, indicating a long-term decrease of Mn input from catchment weathering associated with increasing oxygen content in the paleolake bottom water. The great similarities of the MnHOAc record with other regional and global records suggest that paleolake redox changes and climatic drying in the Qaidam Basin may be largely related to global cooling.

Areal mapping of the middle Wisconsin varved clay site along Sixmile Creek near Ithaca, New York, has revealed a much more widespread and varied array of sediments than previously thought. Lacustrine clays, some varved, are interbedded with sands and gravels interpreted as sub-aqueous fan deposits, and both are overlain by a deformation till. Nine radiocarbon dates indicate a 34–37 14C ka BP age for the lacustrine sediment, with the deformation till less than a few thousand years younger. Beneath this sequence is a deposit dated at ± 42 14C ka BP. Both strata represent a tundra climate with a mean July temperature of about 10°C. The Sixmile Creek deformation till must correlate with the 35 14C ka BP till along the Genesee River, 125 km to the NW, and defines a Cherrytree stade glacial advance into the Appalachian Plateau, much further south than what has generally been accepted. Such an advance would require drainage from a proglacial lake in the western Ontario basin to flow westward instead of northeastward. The Sixmile strata suggest a colder than accepted middle Wisconsin stage. Recent data indicate that this stage is one of progressive cooling, with large climatic fluctuations.

Fire is one of the most important natural disturbances in the coniferous forests of the US Rocky Mountains. The Rocky Mountains are separated by a climatic boundary between 40° and 45° N, which we refer to as the central Rocky Mountains (CRM). To determine whether the fire regime from the CRM was more similar to the northern Rocky Mountains (NRM) or southern Rocky Mountains (SRM) during the Holocene, a 12,539-yr-old sediment core from Long Lake, Wyoming, located in the CRM was analyzed for charcoal and pollen. These data were then compared to charcoal records from the CRM, NRM and SRM. During the Younger Dryas chronozone, the fire regime was characterized as frequent at Long Lake. The early and middle Holocene fire regime was characterized as infrequent. A brief interval from 4000 to 3000 cal yr BP, termed the Populus period, had a frequent fire regime and remained frequent through the late Holocene at Long Lake. In comparison to sites from the NRM and SRM, the fire regime at Long Lake was most similar to the SRM during the past 12,539 cal yr BP. These results suggest the disturbance regime in the CRM has a greater affinity with those of the SRM.

We generated a 5.5-yr snapshot of biweekly-to-monthly resolved time series of carbon and oxygen isotope composition (δ13C and δ18O) and Sr/Ca and Mg/Ca from annually banded aragonite skeleton of a ~ 197 ka pristine Porites coral collected at Niue Island (19°00′S, 169°50′W) in the southwestern subtropical Pacific Ocean. This report is the first of a high-resolution coral-based paleoclimate archive during the Marine Isotope Stage (MIS) 7 interglacial. Statistical results suggest that annual averages of sea-surface temperature (SST) and salinity (SSS) at ~ 197 ka were not significantly different from and ~ 1.2 higher than at present, respectively. Monthly mean variations showed increased SSS at ~ 197 ka that was higher (1.4–1.9 relative to today) in the austral summer than in the austral winter. Monthly SST and SSS anomalies at ~ 197 ka indicated smaller amplitudes by ~ 0.3°C (11%) and ~ 0.3 (24%) relative to the present, possibly suggesting less influence of interannual climate variability around Niue. Our results, taken together with other climate proxy records, imply seasonal and interannual modulation of thermal and hydrological conditions, different from today, in the southwestern subtropical Pacific Ocean associated with the Western Pacific Warm Pool and the South Pacific Convergence Zone variability during the MIS 7 interglacial.

This study establishes a detailed lake-level history for the Lake Superior basin by mapping strandlines from 10-m and 3-m digital elevation models. There are 24 levels above the mid-Holocene Nipissing level, and elevations increase along a direction of 23.1° due to post-glacial rebound. The highest level, the Epi-Duluth, is steeper than subsequent levels and may pre-date the Lake View ice advance into the western Lake Superior basin at the end of the Younger Dryas stade. The most prominent level is the Duluth, ca. 10,800 cal yr BP. Ice retreat exposed successively lower outlets, routing overflow to the Lake Michigan and Huron basins. By 10,600 cal yr BP, lake levels in the western Superior basin had dropped almost 200 m. This transformative period is complicated by multiple basin-wide events: the influx of glacial Lake Agassiz overflow, the creation of three sub-aqueous moraines, and a red to gray color transition in basin sediments. A later drawdown event has been hypothesized to have initiated the 9300 cal yr BP cooling event, but this flood was much smaller than estimated previously. If freshwater triggered the 9300 cal yr BP event, the source of the water must have been Lake Agassiz, not Lake Superior.

Lake Agassiz was ponded on the northward-sloping surface of the Hudson Bay and Arctic Ocean basins, as the Laurentide Ice Sheet retreated. The level of Lake Agassiz abruptly fell ~ 12.9 cal (11 14C) ka BP, exposing the lake floor over a large region for > 1000 yr. The routing of overflow during this (Moorhead low-water) period is uncertain, and there is evidence on the continent and in ocean basins for both an easterly route through the Great Lakes–St. Lawrence to the North Atlantic and for a northwesterly route through the Clearwater–Athabasca–Mackenzie system to the Arctic Ocean. The Moorhead low water phase coincides with the Younger Dryas cooling, and a cause–effect relationship has been proposed by attributing a change in ocean thermohaline circulation to the re-routing of Lake Agassiz freshwaters from the Gulf of Mexico to more northern oceans. Paleoclimatic interpretations from ecosystems in lake sediments in the region, and a simple calculation of the paleohydrological budget of Lake Agassiz, indicate that the climate remained wet and cool throughout the YD in this region, and was not warm nor dry enough to allow evaporative loss to offset the influx of meltwater and precipitation; thus, the Moorhead phase resulted from changes in the outlet that carried overflow.

The rodents from the late middle Pleistocene hominin-bearing locality of J'bel Irhoud include the following species: Meriones shawii, Gerbillus grandis, Dipodillus campestris, Paraethomys ras, Lemniscomys barbarus, Mus cf. spretus, and Eliomys sp. We consider M. shawii, a living species, as identical with the middle Pleistocene Meriones maghrebianus. The mouse differs from the domestic Mus musculus but does not clearly fit into Mus spretus, either. The rare G. grandis looks identical with the form from the middle Pleistocene of Thomas quarries, which may suggest a rather early age for Irhoud. This is in agreement with the occurrence of Paraethomys, a genus unknown in the upper Pleistocene of Morocco, but the absence of the arvicolid Ellobius suggests that the site is younger than other middle Pleistocene sites, Doukkala II, Sidi Abderrahmane D2, and Irhoud-Derbala-Virage. Paleoecological indicators, such as the taxonomic habitat spectrum, or the relative abundances of Gerbillinae and Murinae, suggest a less xeric environment than in many earlier and later sites. Diversity indices, comparable to those of other middle Pleistocene sites, point to similarly favorable conditions before the major climatic crisis close to the middle/upper Pleistocene boundary that drastically reduced rodent diversity in North Africa.

The age of the Great Sand Dunes has been debated for nearly 150 yr. Seven ages ranging from Miocene to late Holocene have been proposed for them. This paper presents new information–chiefly subsurface stratigraphic data, OSL dates, and geomorphic evidence–that indicates that the Great Sand Dunes began to form in the latter part of the middle Pleistocene. The dunes overlie a thick wedge of piedmont-slope deposits, which in turn overlies sediment of Lake Alamosa, a paleolake that began to drain about 440 ka. The wedge of piedmont-slope deposits extends westward for at least 23 km and is as much as 60 m thick at a distance of 10 km from the Sangre de Cristo Range. Ostracodes from one well indicate that the eastern shoreline of Lake Alamosa extended to within 4.3 km of where the Great Sand Dunes eventually formed. The time represented by the wedge of piedmont-slope deposits is not known exactly, but the wedge post-dates 440 ka and was in place prior to 130 ka because by then the dunes overlying it were sufficiently close and tall enough to obstruct streams draining from the Sangre de Cristo Range.

We constrain the history of the Greenland Ice Sheet margin during the Holocene at Upernavik Isstrøm, a major ice stream in northwestern Greenland. Radiocarbon-dated sediment sequences from proglacial-threshold lakes adjacent to the present ice margin constrain deglaciation of the sites to older than 9.6 ± 0.1 ka. This age of deglaciation is confirmed with 10Be ages of 9.9 ± 0.1 ka from an island adjacent to the historical ice position. The lake sediment sequences also constrain the ice margin to have been less extensive than it is today for the remainder of the Holocene until ~ 1100 to ~ 700 yr ago, when it advanced into two lake catchments. The ice margin retreated back out of these lake catchments in the last decade. The early Holocene deglaciation in Melville Bugt, one of few locations around Greenland where a vast stretch of the current ice margin is marine-based, preceded deglaciation in most other parts of Greenland. Earlier deglaciation in this ice-sheet sector may have been caused by additional ablation mechanisms that apply to marine-based ice margins. Furthermore, despite ice-sheet models depicting this sector of Greenland as relatively stable throughout the Holocene, our data indicate a > 20 km advance-retreat cycle within the last millennium.

The Tibetan Plateau is regarded as an amplifier and driver of environmental change in adjacent regions because of its extent and high altitude. However, reliable age control for paleoenvironmental information on the plateau is limited. OSL appears to be a valid method to constrain the age of deposits of glacial and fluvial origin, soils and periglacial structures in the Menyuan basin on the northeastern Tibetan Plateau. Dating results show glaciers advanced extensively to the foot of the Qilian mountains at ~ 21 ka, in agreement with the timing of the global Last Glacial Maximum (LGM) recorded in Northern Hemisphere ice cores. Comparison with results from the eastern Tibetan Plateau suggests that the factor controlling glacial advance in both regions was decreased temperature, not monsoon-related precipitation increase. The areas of the Menyuan basin occupied by glacio-fluvial deposits experienced continuous permafrost during the LGM, indicated by large cryoturbation features, interpreted to indicate that the mean annual temperature was ≥ 7 °C lower than at present. Glacio-fluvial systems in the Menyuan basin aggraded and terraces formed during cold periods (penultimate glaciation, LGM, and possibly the Younger Dryas) as a response to increased glacial sediment production and meltwater runoff then.

In the tropical Mérida Andes (northwestern Venezuela), glacial landforms were found at altitudes between 2600 and 5000 m, corresponding to 600 km2 of ice cover during the maximum glacial extension. However, the lack of sufficient absolute age data prevents detailed reconstruction of the timing of the last deglaciation. On the northwestern flank of the Mucuñuque Massif, successive moraines and striated eroded basement surfaces were sampled for cosmogenic 10Be investigation. Their compilation with published data allows the establishment of a detailed chronology of the post-LGM glacier history. The oldest moraines (18.1 and 16.8 ka) correspond to the Oldest Dryas. Successive moraine ridges indicate stops in the overall retreat between the LGM and the Younger Dryas. The cold and short Older Dryas stadial has been identified. Results indicate that most of the ice withdrew during the Pleistocene. The dataset supports an intensification of the vertical retreat rate from ~ 25 m/ka during the late Pleistocene to ~ 310 m/ka during the Pleistocene/Holocene. Afterwards, the glacier was confined and located in the higher altitude zones. The altitude difference of the Younger Dryas moraines in the Mucubají, La Victoria and Los Zerpa valleys indicates a strong effect of valley orientation on the altitude of moraine development.

We report the first evidence of Hg content in marine sediments changing in connection with the climate-driven changes in ocean stratification during the Quaternary Period based on core samples from ODP Hole 1006A off Great Bahama Bank in the Caribbean Sea. The Hg content ranged from 5.9 to 60.7 ng/g with an average value of 33.1 ng/g during 350 and 1330 ka and changed inversely with δ18Oplanktonic values. The change in Hg content was positively correlated with total organic carbon (TOC) content, indicating connections between the δ15Norg and δ13Corg values of organic matter and the absolute abundance of a deep-dwelling calcareous nannoplankton (Florisphaera profunda). The marine Hg is thought to have been incorporated into the organic matter produced by deep-dwelling phytoplankton. Based on these results, we propose a mechanism by which marine Hg can collect in a thermocline formed in the stratified lower photic zone. Mercury content and nannoplankton assemblage in marine sediment provide information about the extent of stratification of the oceanic photic zone and the role of surface- and deep-dwelling phytoplankton in producing marine organic matter and changing its δ15Norg and δ13Corg values.

Terrestrial meteorite ages indicate that some ice at the Allan Hills blue ice area (AH BIA) may be as old as 2.2 Ma. As such, ice from the AH BIA could potentially be used to extend the ice core record of paleoclimate beyond 800 ka. We collected samples from 5 to 10 cm depth along a 5 km transect through the main icefield and drilled a 225 m ice core (S27) at the midpoint of the transect to develop the climate archive of the AH BIA. Stable water isotope measurements (δD) of the surface chips and of ice core S27 yield comparable signals, indicating that the climate record has not been significantly altered in the surface ice. Measurements of 40Aratm and δ18Oatm taken from ice core S27 and eight additional shallow ice cores constrain the age of the ice to approximately 90–250 ka. Our findings provide a framework around which future investigations of potentially older ice in the AH BIA could be based.

The “espada” speleothems of Cueva de las Espadas (Naica Mine, Chihuahua, Mexico) comprise a high-purity selenite core overlain by successive deposits of calcite, gypsum and aragonite. Gypsum precipitated under water from a hydrothermal solution (~ 58°C) when the water table was above the cave level ca. 57 ka, during the last glaciation, and some intervals during deglaciation and the Holocene. Aragonite was deposited at lower temperatures (~ 26°C) in a perched lake occupying the cave bottom, when the water table dropped below the cave level during brief dry intervals during deglaciation and the early Holocene. The isotopic composition of gypsum water of crystallization shows that the deglaciation–Holocene aquifer water was enriched in deuterium by 12.8–8.7‰ relative to water from the last glaciation. This is attributed to an increased relative moisture contribution from the Gulf of Mexico during deglaciation and the Holocene compared to the last glaciation. This indicates that drier conditions occurred in the Naica area during the Holocene than around 57 ka. Furthermore, trace element analyses of gypsum served to deduce the circulation regime of the Naica aquifer during the past 60,000 yr, and also suggest that higher aquifer recharge occurred during the last glaciation.

This multiproxy study on SE Black Sea sediments provides the first detailed reconstruction of vegetation and environmental history of Northern Anatolia between 134 and 119 ka. Here, the glacial–interglacial transition is characterized by several short-lived alternating cold and warm events preceding a meltwater pulse (~ 130.4–131.7 ka). The latter is reconstructed as a cold arid period correlated to Heinrich event 11. The initial warming is evidenced at ~ 130.4 ka by increased primary productivity in the Black Sea, disappearance of ice-rafted detritus, and spreading of oaks in Anatolia. A Younger Dryas-type event is not identifiable. The Eemian vegetation succession corresponds to the main climatic phases in Europe: i) the Quercus–Juniperus phase (128.7–126.4 ka) indicates a dry continental climate; ii) the Ostrya–Corylus–Quercus–Carpinus phase (126.4–122.9 ka) suggests warm summers, mild winters, and high year-round precipitation; iii) the Fagus–Carpinus phase (122.9–119.5 ka) indicates cooling and high precipitation; and iv) increasing Pinus at ~ 121 ka marks the onset of cooler/drier conditions. Generally, pollen reconstructions suggest altitudinal/latitudinal migrations of vegetation belts in Northern Anatolia during the Eemian caused by increased transport of moisture. The evidence for the wide distribution of Fagus around the Black Sea contrasts with the European records and is likely related to climatic and genetic factors.

A landslide debris field covering ~ 31 km2, the presence of large sediment blocks up to hundreds of meters long, and the exposure of deposits of a single landslide along the incised course of the Quyon River are evidence of a massive failure of sensitive Champlain Sea glaciomarine sediments along the lower Quyon Valley, southwestern Quebec, Canada. Seventeen radiocarbon ages indicate that the failure occurred between 980 and 1060 cal yr BP. Twenty-four additional radiocarbon ages reveal that nine landslides within a 65-km belt in the Quyon"Ottawa area also occurred at approximately this time. In combination, the contemporaneous occurrence of ten landslides between 980 and 1060 cal yr BP, the setting or morphology of five of the other failures, and the close proximity of two of the failures to the Quyon Valley landslide provide circumstantial evidence of a paleoearthquake-triggering mechanism. The paleoearthquake is estimated to be Mw ~ 6.1 or larger, with the epicenter within the West Quebec Seismic Zone. A common earthquake-triggering mechanism for the three largest landslides in eastern Canada suggests a close link between massive failures of sensitive glaciomarine sediments and the regional seismicity.

In order to obtain a better knowledge of past oceanographic variability offshore southern Chile, this study reappraises the changes in the sources of nutrients over the last 25 ka based on a detailed comparison of previously published nitrogen isotope and microfossil records (dinoflagellate cysts, coccoliths and diatoms) from ODP Site 1233 (41°S). Our findings support the main conclusions of Martinez et al. (2006) in the sense that both the Subantarctic Surface Water and the Gunther Undercurrent are potential sources for the recorded late Quaternary sedimentary δ15N signatures at Site 1233, with variable contributions of both sources during different time periods. This study indicates that Subantarctic Surface Water forms the main source for nutrients during the last glacial maximum (25–18.6 cal ka BP), the first part of the deglaciation (18.6–15.7 cal ka BP) and the Holocene (9.8 cal ka BP until present). An increased contribution of Equatorial Subsurface Water as a source of nutrients to the photic zone offshore southern Chile is observed between 14.4 and 9.8 cal ka BP, which is indicative for upwelling conditions at least after 13.2 cal ka BP as indicated by the microfossil data.

Forest fires convert a proportion of the burning vegetation into charcoal that is stored in forest soils and lake sediments. In this paper we use a geostatistical approach to present a detailed analysis of the size of the charcoal pool and its spatial variation in a boreal forest watershed including its lake sediment. The amount of soil charcoal averaged 179 g/m2 and ranged from 0 to 3600 g/m2 in the watershed. There was an extreme variation in the size of the charcoal pool over fine (cm) spatial scales. For example, the amount of charcoal in the soil could range from 34 to 1646 g/m2 within a distance of 10 cm. Individually dated soil charcoal particles had radiocarbon ages that varied from 630 to 2930 cal yr BP. The lake sediment began accumulating at 10,600 cal yr BP and charcoal accumulation has been practically continuous ever since then, with the largest peak occurring at 6900 cal yr BP. The lake sediment contained more charcoal, 360 g/m2, than the average for forest soil. We interpret this as an indication of a relatively rapid degradation of charcoal in boreal forest soils.

Geologic archives show that the Earth was dustier during the last glacial period. One model suggests that increased gustiness (stronger, more frequent winds) enhanced dustiness. We tested this at Loveland, Iowa, one of the thickest deposits of last-glacial-age (Peoria) loess in the world. Based on K/Rb and Ba/Rb, loess was derived not only from glaciogenic sources of the Missouri River, but also distal loess from non-glacial sources in Nebraska. Optically stimulated luminescence (OSL) ages provide the first detailed chronology of Peoria Loess at Loveland. Deposition began after ~ 27 ka and continued until ~ 17 ka. OSL ages also indicate that mass accumulation rates (MARs) of loess were not constant. MARs were highest and grain size was coarsest during the time of middle Peoria Loess accretion, ~ 23 ka, when ~ 10 m of loess accumulated in no more than ~ 2000 yr and possibly much less. The timing of coarsest grain size and highest MAR, indicating strongest winds, coincides with a summer-insolation minimum at high latitudes in North America and the maximum southward extent of the Laurentide ice sheet. These observations suggest that increased dustiness during the last glacial period was driven largely by enhanced gustiness, forced by a steepened meridional temperature gradient.