Latest Quaternary papers

Wednesday, 23 April 2014
Journal of Quaternary Science

Evaluating diatom-derived Holocene pH reconstructions for Arctic lakes using an expanded 171-lake training set

Inference models from diatoms preserved in lake sediments can be used to reconstruct long-term pH changes to better understand the process of lake ontogeny. An expanded diatom training set was developed using taxonomically harmonized modern assemblages in surface sediments of 171 lakes spanning a variety of geological and climatic settings across the Canadian Arctic. Lake-water pH emerged as a significant variable and the most influential in structuring diatom assemblages. The resulting two-component weighted-averaging partial least squares pH inference model performs strongly, even after identifying effects of spatial autocorrelation at distances <20 km. The model was then applied to three dated Holocene diatom stratigraphies from Arctic regions of contrasting bedrock geology and buffering capacity, and the significance of the pH reconstructions was assessed. At Lake CF3 in a poorly buffered catchment, a gradual but significant pH decline begins 5000 years after lake inception, coincident with regional Late Holocene cooling. Reconstructions for two well-buffered, more alkaline sites were not significant, probably due to poor analogues and other factors driving changes in diatom assemblages. Due to sparse soil and vegetation in these and other Arctic basins, bedrock composition is the most important regulator of Holocene pH, and only in poorly buffered lakes does pH primarily represent a climate signal.

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Wednesday, 23 April 2014
Journal of Quaternary Science

Modelling glacier advances and related climate conditions during the last glaciation cycle in the Kuzigun Valley, Tashkurgan catchment, on the north-west Tibetan Plateau

Understanding regional climate during the last glaciation cycle (LGC) is far from complete for the north-western Tibetan Plateau. Recent improvements in understanding glacial extents and chronologies in the Tashkurgan catchment, north-west Tibetan Plateau, present an opportunity to estimate the glacial climatic conditions of the LGC. Here we use a coupled mass-balance and ice-flow model to reconstruct glacier advances in the Kuzigun Valley during the LGC and quantify the related climate conditions in the Tashkurgan, Hangdi, and Kuzigun glacial stages for the region. The model results show that the Kuzigun Valley contained ice volumes of 5.713 ± 0.005, 4.874 ± 0.005 and 3.631 ± 0.004 km3 with equilibrium line altitude-lowering values of ∼500, ∼560 and ∼610 m in the three successive glacial stages, respectively. By referencing the climatic δ18O proxy records, we conclude that temperature decreased by 5–8, ∼4 and <4 °C with precipitation levels of 30–70, ∼100 and >140% modern values in the Kuzigun, Hangdi and Tashkurgan glacial stages, respectively. Our climatic estimates for the Kuzigun stage are generally consistent with previous studies that showed the Last Glacial Maximum climate was 4–9 °C colder than today on the Tibetan Plateau. More accurate climate proxies are needed for evaluating our modelled Tashkurgan climatic conditions.

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Wednesday, 23 April 2014
Journal of Quaternary Science

Hydrology and climatology at Laguna La Gaiba, lowland Bolivia: complex responses to climatic forcings over the last 25 000 years

Diatom, geochemical and isotopic data provide a record of environmental change in Laguna La Gaiba, lowland Bolivia (17°45′S, 57°35′W), over the last ca. 25 000 years. High-resolution diatom analysis around the Last Glacial–Interglacial Transition provides new insights into this period of change. The full and late glacial lake was generally quite shallow, but with evidence of periodic flooding. At about 13 100 cal a BP, just before the start of the Younger Dryas chronozone, the diatoms indicate shallower water conditions, but there is a marked change at about 12 200 cal a BP indicating the onset of a period of high variability, with rising water levels punctuated by periodic drying. From ca. 11 800 to 10 000 cal a BP, stable, deeper water conditions persisted. There is evidence for drying in the early to middle Holocene, but not as pronounced as that reported from elsewhere in the southern hemisphere tropics of South America. This was followed by the onset of wetter conditions in the late Holocene consistent with insolation forcing. Conditions very similar to present were established about 2100 cal a BP. A complex response to both insolation forcing and millennial-scale events originating in the North Atlantic is noted.

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Wednesday, 23 April 2014
Journal of Quaternary Science

Evaluating long-term regional climate variability in the maritime region of the St. Lawrence North Shore (eastern Canada) using a multi-site comparison of peat-based paleohydrological records

This study presents paleohydrological reconstructions from ombrotrophic peatlands (bogs) along the north shore of the Estuary and the Gulf of St. Lawrence in eastern Canada. Past water table depths were reconstructed based on testate amoebae analyses within four peatlands from two maritime ecoclimatic regions (boreal and subarctic) using a new transfer function. The comparison of multiple peat-based paleohydrological records was used to distinguish climate-driven changes from variations related to site-specific factors. Coherence between the water table reconstructions at the regional scale suggests a common climatic influence on bog paleohydrology but there are inconsistencies which also suggest an influence of non-climatic factors (e.g. internal peatland processes and feedbacks). The surface drying and increased hydrological variability after 3000 cal a BP in the studied bogs coincide with the transition from the Holocene Climatic Optimum to the Neoglacial cooling documented by proxy climate records in eastern Canada. The bogs of Havre St-Pierre have experienced major drying during the late Holocene, indicating important annual-to-centennial water deficits at the peatland surface. Regional differences in the magnitude of the hydrological fluctuations may result from distinctive climatic conditions or could indicate that bog surface wetness in the Gulf of St. Lawrence was more sensitive to past climate changes.

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Wednesday, 23 April 2014
Journal of Quaternary Science

Multiproxy diet analysis of the last meal of an early Holocene Yakutian bison

Pollen, botanical macrofossils, chemical components and ancient DNA were studied in samples from the rumen of a frozen Yakutian bison (Bison priscus) that lived ca. 10,500 cal a BP. The dialkyl glycerol ether lipid archaeol (2,3-di-O-phytanyl-sn-glycerol) was detected and is interpreted to have been derived from methanogenic Archaea in the rumen. This is the oldest reported occurrence of archaeol attributed to digestive tract Archaea. Remains of shrubs (Alnus, Betula, Salix) and Poaceae indicate that the animal probably lived in a landscape of predominantly dry soils, intermixed with wetlands containing herbaceous plant species, as indicated by remains of Comarum palustre, Caltha palustris, Eriophorum, Sparganium, Menyanthes trifoliata and Utricularia. All recorded taxa still occur in the present-day Yakutian tundra vegetation. We discuss the representativeness in space and time of the methods used. Both the botanical microfossil and the macrofossil records may be biased because of differences in pollen production and dispersal between species, the food choice of the bison, and the season of death of the animal. Similarities and differences are discussed to highlight pitfalls of the individual analytical techniques. We highlight the power of data integration.

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Wednesday, 23 April 2014
Journal of Quaternary Science

Diversity dynamics of the Late Cenozoic rodent community from south-western Kansas: the influence of historical processes on community structure

This study used the dense late Cenozoic rodent record of south-western Kansas to test for an equilibrium in species richness through millions of years, identify and clarify historical influences on species richness, determine the relative contribution of immigration, speciation and local extinction to species originations at the community level, and calculate background extinction rates to compare with modern species losses due to anthropogenic activities. The Meade Basin rodent community has been in equilibrium, with an average of about 17 species, for almost 5 million years. No speciation events were identified in the Meade Basin rodent record; although speciation ultimately contributes to the regional species pool, local speciation events contributed little to community structure. Extinctions and immigrations continued through the study period, with elevated bouts of turnover correlated with global cooling events and lowered sea level associated with the Beringian land bridge. Turnover was generated primarily by stochastic climatic agents at several temporal scales, possibly including rapid and devastating regional volcanic ashfalls. None of the extinction rates recorded in the Meade Basin system rivals extinction levels in modern species due to anthropogenic activities.

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Wednesday, 23 April 2014
Journal of Quaternary Science

Tracing long-term tropical montane ecosystem change in the Eastern Arc Mountains of Tanzania

Pollen, charcoal, stable carbon and nitrogen isotope, and radiocarbon analyses are used to reconstruct a palaeoenvironmental record from the Eastern Arc Mountains (EAM), Tanzania, dating back >45 000 years. A sedimentary hiatus covering the last glacial-interglacial transition (LGIT) and early to mid Holocene follows the lead up to the Last Glacial Maximum (LGM) period. A late Holocene portion of the record is included as a modern analogue. Before 45 000 cal a BP, very low regional pollen counts imply open vegetation surrounding the site. Subsequently, the development of extensive montane forest characterizes a relatively mesic pre-LGM. The transition into the LGM witnessed a marked shift from C3- to C4-dominated biomass, representing an expansion of open forest dominated by grasses. These changes may be attributed to a combination of enhanced moisture stress and CO2 limitation, factors that may have been exacerbated by an intensive fire regime, as evident from the charcoal record. This is supported by a decrease in montane forest taxa, coupled with an associated expansion of C4 graminoids and ericaceous heathland to form a montane grassland mosaic similar to that previously recorded on other East African mountains around the time of the LGM but not, to date, having been shown in the Eastern Arc Mountains.

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Wednesday, 23 April 2014
Journal of Quaternary Science

A 560–440 ka tephra record from the Mercure Basin, southern Italy: volcanological and tephrostratigraphic implications

Integrated electron microprobe analyses (EMPAs) on glass and Sr–Nd isotope analyses have been performed on 17 tephras from the Middle Pleistocene Mercure lacustrine succession, southern Apennines. Two 40Ar/39Ar ages and the recognition of four relevant tephras from Colli Albani, Sabatini and possibly Roccamonfina volcanoes allowed us to ascribe the investigated succession to the late Marine Isotope Stage (MIS) 15–12 interval (560–440 ka). The Sr–Nd isotopes and major element glass compositions allowed us to attribute 10 out of the other 13 tephras to a poorly known activity of the Roccamofina volcano, whereas two layers were tentatively attributed to previously unknown Middle Pleistocene activity of Ponza Island or Campanian volcanoes, and one to Salina Island. The tephrostratigraphic correlation of the Mercure tephras with the Acerno lacustrine pollen record (Campania) also allowed us to evaluate the climatostratigraphic position of the tephras within the framework of the MIS 15–12 climatic variability. These results were obtained by combining the Sr–Nd isotope ratio with EMPA and 40Ar/39Ar geochronological data. This confirms the notable consistency of this approach for studying the Mediterranean Middle Pleistocene tephrostratigraphy, which, despite its great potential for both volcanology and Quaternary studies, has been hitherto barely explored.

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Friday, 18 April 2014
Earth and Planetary Science News

Analytic investigations of CNFP-based self-deicing road system on the deicing performance

H. Li

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Friday, 18 April 2014
Earth and Planetary Science News

Crustal structure and inferred rifting processes in the northeast South China Sea

K. McIntosh

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Friday, 18 April 2014
Earth and Planetary Science News

Fluvial evolution of the Rhine during the last interglacial-glacial cycle in the southern North Sea basin: A review and look forward

J Peeters

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Friday, 18 April 2014
Earth and Planetary Science News

Freezing and thawing characteristics of frozen soils: Bound water content and hysteresis phenomenon

H. Tian

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Friday, 18 April 2014
Earth and Planetary Science News

Hardness estimation and weak layer detection in simulated snow stratigraphy

F. Monti

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Friday, 18 April 2014
Earth and Planetary Science News

Mythic codes of the Mezinian

M. Otte

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Friday, 18 April 2014
Earth and Planetary Science News

Projected precipitation and streamflow under SRES and RCP emission scenarios in the Songhuajiang River basin, China

Buda Su, Xiaofan Zeng, Jianqing Zhai, Yanjun Wang, Xiucang Li

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Friday, 18 April 2014
Earth and Planetary Science News

Sequence stratigraphic modelling and reservoir architecture of the shallow marine successions of Baram field, West Baram Delta, Offshore Sarawak, East Malay

A. Hadi

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Friday, 18 April 2014
Earth and Planetary Science News

The thermal budget evaluation of the two-phase closed thermosyphon embankment of the Qinghai-Tibet Highway in permafrost regions

D. Wu

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Thursday, 17 April 2014
Boreas

Late Pleistocene stratigraphy and sedimentary environments of the Severnaya Dvina-Vychegda region in northwestern Russia

The Late Pleistocene stratigraphy from the Severnaya Dvina-Vychegda region of northwestern Russia is revised based on investigations of new localities, revisiting earlier localities, introduction of about 110 new OSL dates and burial depth corrections of earlier published OSL dates, in addition to six new radiocarbon dates. Most of the OSL samples studied here are from fluvial and subaquaeous sediments, which we found to be well bleached. Six chronostratigraphical units and their sedimentary environment are described, with the oldest unit consisting of pre-Eemian glacial beds. For the first time, Early Weichselian sediments are documented from the region and a fluvial environment with some vegetation and permafrost conditions is suggested to have persisted from the end of the Eemian until at least about 92 ka ago. The period in which a Middle Weichselian White Sea Lake could have existed is constrained to 67−62 ka, but as the lake level never reached the thresholds of the drainage basin, the lake probably existed only for a short interval within this time-span. Blocking and reversal of fluvial drainage started again around 21−20 ka ago when the Fennoscandian Ice Sheet advanced into the area, reaching its maximum 17−15 ka ago. At that time, an ice-dammed lake reached its maximum water level, which was around 135 m above present sea level. Drainage of the lake started shortly after 15 ka ago, and the lake was emptied within 700 years. Severe periglacial conditions, with permafrost and aeolian activity, prevailed in the area until about 10.7 ka.

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Friday, 11 April 2014
Boreas

Late Quaternary (Marine Isotope Stage 3 to Recent) sedimentary evolution of the Basque shelf (southern Bay of Biscay)

Late Quaternary (MIS 3 to Recent) oceanographic evolution of the Basque shelf has been analysed for the first time based on the sedimentological analysis of three cores obtained from the middle and outer shelves. The cores are located in two interfluves separated by the San Sebastian canyon. The variability of the percentage of the planktonic foraminifera species Neogloboquadrina pachyderma sin. and of δ18Obull allowed us to identify the influence of colder and warmer waters in the Basque shelf during the late Quaternary. From ∼56 cal. ka BP to the end of the Last Glacial Maximum (19 cal. ka BP) the sedimentary record shows a decreasing trend in the mean grain size that correlates with the eustatic sea-level fall. The last Deglaciation (19–11.5 cal. ka BP) is characterized by a sea-level rise that produced an important hiatus in the western outer shelf. During the Holocene, the middle and outer shelves present different behaviours. From 11.5 to 6.7 cal. ka BP, in the outer shelf the sea-level rise that started during the Deglaciation produced a hiatus, whereas in the middle shelf the sedimentary succession records the presence of warm to temperate waters. Between 6.7–4.9 cal. ka BP, the entrance of cold surface water-masses that only affected the middle shelf has been identified, and temperate to warm waters occurred in the outer shelf. The cold surface water-masses retreated during 4.9–4.3 cal. ka BP in the middle shelf. Finally, from 4.3 cal. ka BP to Recent, the middle shelf registers a hiatus due to sea-level stabilization after a generalized transgression, synchronous to a decrease in the energy of the water-masses in the outer shelf. In conclusion, the environmental changes detected in the Basque shelf are attributed to both regional and eustatic sea-level changes.

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Tuesday, 08 April 2014
Boreas

Palaeoecological, archaeological and historical data and the making of Devon landscapes. I. The Blackdown Hills

This paper presents the first systematic study of the vegetation history of a range of low hills in SW England, UK, lying between more researched fenlands and uplands. After the palaeoecological sites were located bespoke archaeological, historical and documentary studies of the surrounding landscape were undertaken specifically to inform palynological interpretation at each site. The region has a distinctive archaeology with late Mesolithic tool scatters, some evidence of early Neolithic agriculture, many Bronze Age funerary monuments and Romano-British iron-working. Historical studies have suggested that the present landscape pattern is largely early Medieval. However, the pollen evidence suggests a significantly different Holocene vegetation history in comparison with other areas in lowland England, with evidence of incomplete forest clearance in later-Prehistory (Bronze−Iron Age). Woodland persistence on steep, but poorly drained, slopes, was probably due to the unsuitability of these areas for mixed farming. Instead they may have been under woodland management (e.g. coppicing) associated with the iron-working industry. Data from two of the sites also suggest that later Iron Age and Romano-British impact may have been geographically restricted. The documented Medieval land management that maintained the patchwork of small fields, woods and heathlands had its origins in later Prehistory, but there is also evidence of landscape change in the 6th–9th centuries AD. We conclude that the Blackdown Hills area was one of many ‘distinctive subregions’, which due to a combination of edaphic, topographic and cultural factors could qualify as an eco-cultural region or ‘pays’. It is argued that the use of such eco-culturally distinctive regions or pays can provide a spatial and archaeological framework for palaeoecology, which has implications for landscape research, designation and heritage management.

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