Latest Quaternary papers

Tuesday, 19 August 2014
Earth and Planetary Science News

• Determination of sea-floor seepage locations in the Mississippi Canyon

Emma Crooke

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Tuesday, 19 August 2014
Earth and Planetary Science News

• Different expressions of rifting on the South China Sea margins

• D. Savva, M. Pubellier, D. Franke, N. Chamot-Rooke, F. Meresse, S. Steuer, J.L. Auxietre

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Tuesday, 19 August 2014
Earth and Planetary Science News

• Evaluation of a snow avalanche possibly triggered by a local earthquake at Vallée de la Sionne, Switzerland

• C. Pérez-Guillén, M. Tapia, G. Furdada, E. Suriñach, J.N. McElwaine, W. Steinkogler, M. Hiller

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Tuesday, 19 August 2014
Earth and Planetary Science News

• Grain-scale imaging and compositional characterization of select India NGHP Expedition-01 gas-hydrate-bearing cores, and comparison to other natural gas hydrates

• Laura A. Stern, Thomas D. Lorenson

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Tuesday, 19 August 2014
Earth and Planetary Science News

• Investigation of vegetation history of buried chernozem soils using near-infrared spectroscopy (NIRS)

• Barbora Vysloužilová, Damien Ertlen, Luděk Šefrna, Tibor Novák, Klára Virágh, Mathieu Rué, Arnaud Campaner, Dagmar Dreslerová, Dominique Schwartz

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Tuesday, 19 August 2014
Earth and Planetary Science News

• Numerical modeling of slope flows entraining bottom material

• M.E. Eglit, A.E. Yakubenko

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Tuesday, 19 August 2014
Earth and Planetary Science News

• Soil and sediment archives of ancient landscapes, paleoenvironments, and archaeological site formation processes

• Kathleen Nicoll, Laura R. Murphy

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Tuesday, 19 August 2014
Earth and Planetary Science News

• Study on Thermal Regime of Roadbed-Culvert Transition Section along a High Speed Railway in Seasonally Frozen Regions

• Liu Hua, Niu Fujun, Niu Yonghong, Yang Xifeng

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Wednesday, 13 August 2014
Journal of Quaternary Science

The use of multivariate statistics to resolve multiple contamination signals in the oxygen isotope analysis of biogenic silica

Analysis of the oxygen isotope composition (δ18O) of diatom silica is a commonly used tool for palaeoclimate reconstruction that recent studies have demonstrated may be complicated by the presence of non-diatom detrital material. Such contamination can mask any true climate-driven signal, leading to spurious results. Analysis of the 2.6-Ma Barsemoi diatomites from the East African Rift Valley highlights the presence of both tephra and clay in purified samples. Here we present a new method for assessing the relative contribution and geochemical composition of contamination components where sedimentary samples may be affected by more than one type of contamination. This approach shows that the incorporation of analytical techniques, such as X-ray fluorescence spectrometry, coupled with statistical modelling, can be used to develop a three end-member model to successfully resolve climate-driven changes in δ18Odiatom. Mass-balance corrections made to δ18Odiatom data demonstrate the importance of adopting quantitative geochemical analysis in tandem with the δ18O analysis of biogenic silica, to obtain accurate and meaningful results for palaeoclimate reconstruction.

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Friday, 08 August 2014
Journal of Quaternary Science

The Younger Dryas impact hypothesis: a cosmic catastrophe

In this paper we review the evidence for the Younger Dryas impact hypothesis (YDIH), which proposes that at ∼12.9k cal a BP North America, South America, Europe and the Middle East were subjected to some sort of extraterrestrial event. This purported event is proposed as a catastrophic process responsible for: terminal Pleistocene environmental changes (onset of YD cooling, continent-scale wildfires); extinction of late Pleistocene mammals; and demise of the Clovis ‘culture’ in North America, the earliest well-documented, continent-scale settlement of the region. The basic physics in the YDIH is not in accord with the physics of impacts nor the basic laws of physics. No YD boundary (YDB) crater, craters or other direct indicators of an impact are known. Age control is weak to non-existent at 26 of the 29 localities claimed to have evidence for the YDIH. Attempts to reproduce the results of physical and geochemical analyses used to support the YDIH have failed or show that many indicators are not unique to an impact nor to ∼12.9k cal a BP. The depositional environments of purported indicators at most sites tend to concentrate particulate matter and probably created many ‘YDB zones’. Geomorphic, stratigraphic and fire records show no evidence of any sort of catastrophic changes in the environment at or immediately following the YDB. Late Pleistocene extinctions varied in time and across space. Archeological data provide no indication of population decline, demographic collapse or major adaptive shifts at or just after ∼12.9 ka. The data and the hypotheses generated by YDIH proponents are contradictory, inconsistent and incoherent.

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Friday, 08 August 2014
Journal of Quaternary Science

Luminescence chronology of late Quaternary moraines and Last Glacial Maximum equilibrium-line altitude reconstruction from Parlung Zangbo Valley, south-eastern Tibetan Plateau

Optically stimulated luminescence dating was applied to samples from glacial sediments in the Parlung Zangbo Valleys (Daba and Charao) of the south-eastern Tibetan Plateau to better constrain the timing of Late Quaternary glaciation, which is thought to have been linked to the Indian monsoon. The single aliquot regenerative-dose protocol on quartz was used for equivalent dose (De) determination using small aliquots. For samples from the Daba Valley, the comparison of ages using two grain size fractions, middle (38–63 µm) and coarse (90–250 µm) were conducted. The coarse grain ages in the Daba Valley (P3) and Charao Valley (P7) range from 16.4 to 26.0 ka, and are consistent with previously published cosmogenic radionuclide exposure ages in the Baiyu Valley (PB1). Our dating results reveal that these moraines were formed during the Last Glacial Maximum (LGM). We then reconstruct the past equilibrium-line altitudes (ELAs) during the LGM for five glacial valleys in the study area, which range from 3286 to 4014 m with an average value of 3730 m, while the contemporary average ELA is 4655 m. After correction for terrain uplift (about 8 m since the LGM), the difference in the ELA values between the LGM and today is 917 m. According to these data, the estimated temperature during the LGM is 6.3 °C lower than present for the Parlung Zangbo River Valley.

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Friday, 08 August 2014
Journal of Quaternary Science

The relative controls on forest fires and fuel source fluctuations in the Holocene deciduous forests of southern Wisconsin, USA

Reconstructing fire regimes and fuel characteristics is an important aspect of understanding past forest ecosystem processes. Fuel sources and fire regimes in the upper Midwestern United States have been shown to be sensitive to regional climatic variability, such as drought periods on millennial timescales. Yet, records documenting the connections between disturbance activity and the corresponding fuel source fluctuations in mesic deciduous forests and prairie/oak savanna in this region are limited. Thus, it has been difficult to provide a framework to evaluate changes in moisture availability on fire activity and the relationships with fuel source fluctuations in this region. We present high-resolution charcoal analyses of lake sediments from four sites in southern Wisconsin (USA) to characterize fire activity and fuel source fluctuation in mesic deciduous forests and prairie/oak savanna over the last 10 000 years. We found that fire occurrence across the four study sites has been asynchronous throughout the Holocene, because of site-specific differences that have strongly influenced local fire regimes. Additionally, we found that during periods of high fire activity the primary fuels were from arboreal sources, and during periods of low fire activity the primary fuels were from non-arboreal sources. However, fluctuations in fuel sources did not always correspond to changes in vegetation, or changes in fire frequency.

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Friday, 08 August 2014
Journal of Quaternary Science

Orbital- and millennial-scale climate and vegetation changes between 32.5 and 6.9k cal a BP from Hanon Maar paleolake on Jeju Island, South Korea

Orbital- and millennial-scale climate and vegetation changes between 32.5 and 6.9k cal a BP from Hanon Maar paleolake on Jeju Island, Korea, were demonstrated by high-resolution multi-proxy data (pollen, magnetic susceptibility, total organic carbon, carbon/nitrogen ratios and sediment grain size). High-resolution pollen records provided detailed information on the vegetation response to climate change. The Thalictrum pollen percentage, which corresponded to the magnetic susceptibility data, and the first principal component of principal-component analysis of pollen data were good indicators of the orbital- and millennial-scale dry/wet cycle in the study area. Hanon pollen and magnetic susceptibility records suggested that colder and drier conditions were prevalent between 25.2 and 17.6k cal a BP in the study area due to a precession-induced decrease in summer insolation. Hanon multi-proxy data were correlated with oxygen isotope records from Greenland and Hulu cave, suggesting the possible teleconnection of millennial-scale climate oscillations between North Atlantic and East Asian regions. According to our results, Heinrich-like cold events probably occurred around 31.1, 25.2 and 16.7k cal a BP, and the warm intervals observed around 30.7 and 29.9k cal a BP may have corresponded to Dansgaard–Oeschger warm events 4 and 3, respectively.

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Friday, 08 August 2014
Journal of Quaternary Science

Volcanic stratigraphy of the Quaternary La Garrotxa Volcanic Field (north-east Iberian Peninsula)

The monogenetic Quaternary La Garrotxa Volcanic Field forms part of the Catalan Volcanic Zone (north-east Iberian Peninsula), one of the alkaline volcanic provinces of the European rift system. It harbours more than 50 basaltic monogenetic cones that range in age from the Middle Pleistocene to the Early Holocene and include cinder and scoria cones, lava flows, tuff rings and maars. This study is the result of extensive fieldwork, including the study of ephemeral outcrops and the stratigraphic logging of new water wells and geotechnical drill holes, also taking into account existing information gathered by recent geophysical studies that have applied shallow geophysical methods to establish the substrate geology of this volcanic field. We have obtained a comprehensive volcanic stratigraphy of the area that identifies the products of each single eruption, their relative stratigraphy and their surface area. This volcanic stratigraphy constitutes an essential tool for understanding the evolution of this volcanic field and for establishing a correct volcanic hazard assessment for the area, but it also provides a precise reference for the Quaternary tephrochronology of the lake sediments in neighbouring areas.

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Friday, 08 August 2014
Journal of Quaternary Science

Re-evaluation of the Roseau Tuff eruptive sequence and other ignimbrites in Dominica, Lesser Antilles

The island of Dominica hosts several ignimbrites, including the Roseau Tuff, thought to represent the largest eruption in the Caribbean in the past 200 000 years. The volcanic stratigraphy of the island is poorly understood due to limited outcrops and a paucity of geochemical and geochronological data. The discovery of a new fully accessible exposure of three ignimbrites intercalated with paleosols provides an opportunity to re-evaluate the current stratigraphic framework of ignimbrite-forming eruptions on the island. Whole-rock analyses of pumice clasts from Dominica ignimbrites are andesitic (61–66% SiO2) and in most cases are geochemically indistinguishable. Ignimbrites in the north of the island have less evolved glass compositions (73–75% SiO2) and more mafic orthopyroxene compositions (En > 56) than their southern counterparts (75–78% SiO2; En < 56). Pumice clasts from ignimbrites in southern Dominica have indistinguishable groundmass glass and mineral chemistry, making correlation of these deposits difficult. New (U–Th)/He eruption ages for the southern ignimbrites indicate that at least six separate explosive eruptions occurred between 24 and 61 ka. The non-unique geochemistry of these deposits, together with the new (U−Th)/He ages, suggests that the large volume inferred for the Roseau Tuff eruption may actually be a composite of six smaller, geochemically homogeneous eruptions.

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Friday, 08 August 2014
Journal of Quaternary Science

A natural experiment suggests little direct temperature forcing of the peatland palaeoclimate record

An important uncertainty in the interpretation of peat-based Holocene climate reconstructions is what aspect of climate is recorded. Testate amoeba palaeoecological records have generally been interpreted in terms of water table depth but an increasing weight of experimental evidence shows that testate amoeba communities may respond to temperature independent of hydrological variability. In most ombrotrophic peatlands, variability in water table depth is driven by a combination of both temperature and precipitation, making it difficult to isolate any direct forcing by temperature. An unusual peatland ecosystem in which water tables are extremely stable offers an approach to this question. If testate amoeba communities show variability through time in these percolation bogs this implies a direct influence of temperature. This study presents a late Holocene testate amoeba record from the Imnati percolation bog in western Georgia. Below a phase of recent eutrophication results show essentially no variability in testate amoeba community composition or inferred water table depth through more than 4 m of peat representing over 2000 years. It is improbable that there has been no temperature variability over this period and the data therefore imply that direct temperature forcing of the palaeoecological record is minimal, at least for this region and time-scale.

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Friday, 08 August 2014
Journal of Quaternary Science

Quaternary climatic instability in south-east Australia from a multi-proxy speleothem record

Milankovitch-scale Quaternary climatic oscillations within south-east Australia are known to be characterized by relatively arid glacial and wet interglacial stages. However, terrestrial proxy records of environmental change are scarce, based largely on river terraces, dune sediments and pollen sequences. Here we present a speleothem-based palaeoclimate record from Yarrangobilly caves, south-east Australia. The oxygen isotopic composition of calcite (δ18Ocalcite) is taken to represent rainfall amount and used as an aridity index. High-resolution trace element profiles and UV fluorescence support interpretations based on δ18Ocalcite, allowing further designation of key phases of speleothem growth into periods of relative aridity and moisture excess. A hiatus of approximately 37 ka duration divides the record into two key phases of growth which can be mapped onto marine isotope stages 5c–a and 3, respectively. Increasing aridity in the latter half of MIS 5 led to cessation of speleothem growth for the duration of MIS 4. Growth recommences during MIS 3, associated with greater moisture availability, enhanced vegetation and augmented biogeochemical cycling. This speleothem record provides a unique context of terrestrial environmental change and depicts hydrological conditions which fluctuate markedly over the 70-ka period covering the time of megafauna extinction and human arrival on the continent.

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Thursday, 07 August 2014
Boreas

Timing and preservation mechanism of deglacial pteropod spike from the Andaman Sea, northeastern Indian Ocean

The aragonite compensation depth (ACD) fluctuated considerably during the last glacial until the Holocene with a dominant pteropod preservation spike during the deglacial period, which is prominently seen in three well-dated cores covering the Andaman Sea, northeastern Indian Ocean. The precise time period of the preservation spike of pteropods is not known but this knowledge is crucial for stratigraphical correlation and also for understanding the driving mechanism. Isotopic and foraminiferal proxies were used to decipher the possible mechanism for pteropods preservation in the Andaman Sea. The poor preservation/absence of pteropods during the Holocene in the Andaman Sea may have implications for ocean acidification, driven by enhanced atmospheric CO2 concentration. Strengthening of the summer monsoon and the resultant high biological productivity may also have played a role in the poor preservation of pteropods. The deglacial pteropod spike is characterized by high abundance/preservation of the pteropods between ∼19 and 15 cal. ka BP, associated with very low atmospheric CO2 concentration. Isotope data suggest the prevalence of a glacial environment with reduced sea surface temperature, upwelling and enhanced salinity during the pteropod preservation spike. Total planktic foraminifera and Globigerina bulloides abundances are low during this period, implying a weakened summer monsoon and reduced foraminiferal productivity. Based on the preservation record of pteropods, it is inferred that the ACD was probably deepest (>2900 m) at 16.5 cal. ka BP. The synchronous regional occurrence of the pteropod preservation spike in the Andaman Sea and in the northwestern Indian Ocean could potentially be employed as a stratigraphic marker.

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Thursday, 07 August 2014
Boreas

Palaeoceanographic development in Storfjorden, Svalbard, during the deglaciation and Holocene: evidence from benthic foraminiferal records

Brines can have a profound influence on the relative abundance of calcareous and agglutinated foraminiferal faunas. Here we investigated the distribution of benthic foraminiferal species in four cores from a brine-enriched environment in Storfjorden, Svalbard. Stratigraphically, the cores comprise the last 15 000 years. The purpose of the study was to reconstruct changes in the palaeoecology and palaeoceanography of Storfjorden in relation to past climate changes, and to identify potential indicator species for brine-affected environments. The benthic foraminifera in Storfjorden all have widespread occurrences in the Arctic realm. Calcareous species dominated Storfjorden during the deglaciation and early Holocene until c. 8200 a BP. However, agglutinated species increased in abundance whenever conditions became colder with more sea ice and stronger brine formation, such as during the Older Dryas, the Intra-Allerød Cold Period and the Younger Dryas. Following a moderately cold period with numerous agglutinated foraminifera from c. 8200–4000 a BP, conditions became more changeable from c. 4000 a BP with repeated shifts between warmer periods dominated by calcareous species and colder periods dominated by agglutinated species. The warmer periods show a stronger influence of Atlantic Water, with reduced brine formation and less corrosive conditions at the sea bottom. Conversely, the colder periods show a stronger influence of Arctic water, with higher brine production and more corrosive bottom water. The distribution patterns of the calcareous species are basically the same whether calculated relative to the total fauna (including agglutinated specimens) or relative to calcareous specimens alone. Moreover, the patterns are similar to the patterns found elsewhere along western Svalbard in areas without the influence of brines. No particular species appear to be specifically linked to brine formation. However, the most persistent agglutinated species R. scorpiurus and A. glomerata are also the species most tolerant of the acidic bottom water that normally is associated with brine formation.

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Thursday, 07 August 2014
Boreas

Late Quaternary glaciation in the Hebrides sector of the continental shelf: was St Kilda overrun by the British-Irish Ice Sheet?

Until recently, the British-Irish Ice Sheet (BIIS) was thought to have reached no farther than a mid-continental shelf position in the Hebrides Sector, NW Britain, during the last glaciation (traditional model). However, recent discovery of widespread shelf-edge moraines in this sector has led to a suggestion of much more extensive ice (Atlantic Shelf model). The position of the St Kilda archipelago, approximately mid-way between the Outer Hebrides and the continental shelf edge, makes it ideal as an onshore location to test which of the two competing models is more viable. To this end, we (i) reassessed the characteristics, stratigraphy and morphology of the Quaternary sediments exposed on the largest island (Hirta), and (ii) applied time-dependent 2D numerical modelling of possible glacier formation on Hirta. Instead of three glaciations (as previously suggested), we identified evidence of only two, including one of entirely local derivation. The numerical model supports the view that this glaciation was in the form of two short glaciers occupying the two valleys that dominate Hirta. The good state of preservation of the glacial sediments and associated moraine of this local glaciation indicate relatively recent formation. In view of the low inferred equilibrium line altitude of the glacier associated with the best morphological evidence (∼120 m), considerable thickness of slope deposits outside the glacial limits and evidence of only one rather than two tills, a Late Devensian rather than Younger Dryas age is preferred for this glaciation. Re-examination of the submarine moraine pattern from available bathymetry suggests that the ice sheet was forced to flow around St Kilda, implying that the ice was of insufficient thickness to overrun the islands. Accepting this leaves open the possibility that a St Kilda nunatak supported local ice while the ice sheet extended to the continental shelf edge.

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