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  • In the unglaciated areas of Antarctica, lake sediments act as archives of the regional environmental and climatic history. In most cases, the records are restricted to the Holocene. Amongst the few exceptions are lakes in the McMurdo Dry Valleys, southern Victoria Land, which are known to have remained mostly ice-free during the Last Glacial Maximum. Within the scope of an U.S.-American-German expedition in austral summer 2002/2003, several sediment cores were recovered from the three major lakes in the Taylor Valley: lakes Fryxell, Hoare, and Bonney. In order to reconstruct the late Quaternary regional environmental and climate history, sedimentological, biogeochemical, mineralogical, and chronological investigations were conducted on the sediment sequences recovered from Lake Hoare (core Lz1020) and East Lake Bonney (core Lz1023) within the scope of this thesis. Sediment cores from Lake Hoare with a maximum length of 2.3 m mainly consist of coarse-grained material and penetrate back into the late Weichselian, when Taylor Valley was occupied by the large proglacial Lake Washburn. This lake was dammed by the advanced Ross Sea ice sheet at the valley outlet and was mainly fed by meltwater of the ice sheet. During the Pleistocene-Holocene transition, enhanced evaporation led to a significant lake level drop of Lake Washburn ...,thesis,
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  • The magnetic properties of a sediment core from a high altitude lake in the Swiss Alps were compared with palynological and geochemical data to link climatic and mineral magnetic variations. According to pollen data, the sediments extend from the present to the Younger Dryas, i.e., they cover more than 10,000 years of environmental change in the Alps. The major change in magnetic properties corresponds to the climatic warming of the early Holocene. High-coercivity magnetic minerals that characterize the Late Glacial period almost disappeared during the Holocene and the concentration of ferrimagnetic minerals increased sharply. The contribution of superparamagnetic grains also decreased in the Holocene sediments. Similar variations in {SP} content and coercivity, of smaller magnitude, are found in the Holocene and are interpreted to represent minor climatic variations. Comparison with the historical record of the last 1000 years confirms this interpretation. The magnetic mineralogy, the superparamagnetic contents, and the {IRM} intensity in the coarse-grained, Late Glacial sediments are similar to those measured in the catchment bedrock. This indicates a detrital origin. The different properties and the higher concentration of magnetic minerals in the Holocene sediments are due to authigenic phases. Magnetic properties provide a high resolution record of climatic change. They are sensitive even to small variations that are not recorded in the pollen or {LOI} data. Magnetic parameters show fine-scale variation and constitute a valuable supplement to conventional climatic indicators.
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  • Organic matter deposited in ancient, ice-rich permafrost sediments is vulnerable to climate change and may contribute to the future release of greenhouse gases; it is thus important to get a better characterization of the plant organic matter within such sediments. From a Late Quaternary permafrost sediment core from the Buor Khaya Peninsula, we analysed plant-derived sedimentary ancient DNA (sedaDNA) to identify the taxonomic composition of plant organic matter, and undertook palynological analysis to assess the environmental conditions during deposition. Using sedaDNA, we identified 154 taxa and from pollen and non-pollen palynomorphs we identified 83 taxa. In the deposits dated between 54 and 51 kyr BP, sedaDNA records a diverse low-centred polygon plant community including recurring aquatic pond vegetation while from the pollen record we infer terrestrial open-land vegetation with relatively dry environmental conditions at a regional scale. A fluctuating dominance of either terrestrial or swamp and aquatic taxa in both proxies allowed the local hydrological development of the polygon to be traced. In deposits dated between 11.4 and 9.7 kyr BP (13.4-11.1 cal kyr BP), sedaDNA shows a taxonomic turnover to moist shrub tundra and a lower taxonomic richness compared to the older samples. Pollen also records a shrub tundra community, mostly seen as changes in relative proportions of the most dominant taxa, while a decrease in taxonomic richness was less pronounced compared to sedaDNA. Our results show the advantages of using sedaDNA in combination with palynological analyses when macrofossils are rarely preserved. The high resolution of the sedaDNA record provides a detailed picture of the taxonomic composition of plant-derived organic matter throughout the core, and palynological analyses prove valuable by allowing for inferences of regional environmental conditions.,Postprints der Universität Potsdam : Mathematisch-Naturwissenschaftliche Reihe, 670,
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  • Location and lithology of the short cores collected in the eastern part of Puyehue Lake. The upper part of PU-II long core is also represented. Based on the nature of the heavy mineral fraction, correlations between cores are proposed. Tephras T1 and T2 do not contain heavy minerals and have a similar geochemical composition. They are therefore correlated according to macroscopical descriptions only. Tephras have been attributed the following ages: T1: AD 1960; T2: AD 1921–22; T3: AD 1907; T4: AD 1575; T5: unknown. See text for details. ... Bulk grain-size distribution of 3 typical tephra samples occurring in PU-II long core. All the samples contain a mixture of tephra particles and host sediment. Tephra grains were separated from the host sediment by sieving the samples at 75 and 420 µm (see text). (A) PU-II-500: sample dominated by coarse tephra particles, where the host sediment only represents 10% of the total sample and is completely discarded after sieving at 75 µm; (B) PU-II-744: sample composed of a mixture of coarse tephra particles and host sediment. Particles coarser than 75 µm may contain host sediment; (C) PU-II-179: fine tephra layer. In this case the >75 µm fraction does not contain all the tephra particles. ... Bulk and heavy mineralogy of the 15 thickest tephra layers collected in PU-II long core. In addition, the three youngest tephras (PU-II-16, 59 and 79) are also represented. See Supplementary Table 2 for more details. ... Geomorphology and Quaternary Geology, University of Liège, Belgium... Similarity coefficient (SC) calculations (after Borchardt et al, 1972) comparing major element analysis of tephras from PU-II-P2 and PU-I-P1 short cores ... AMS radiocarbon ages obtained on bulk sediment samples bracketing the T3 tephra in PU-I-P1 and PU-II-P2 short cores ... Lake sediments
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  • List of volcanic centres in southern Chile and Argentina with strong evidence for late Quaternary (post-glacial) activity, modified from Siebert et al. (2010). Arc segments: SVZ = Southern Volcanic Zone (N = North, T = Transitional, C = Central, S = South), AVZ = Austral Volcanic Zone, BA = back-arc volcanoes, after Stern (2004). Old GVP number refers to the indexing used by Siebert et al. (2010); VNum refers to the updated indexing introduced by GVP online (http://volcano.si.edu). Additional information on largest eruptions can be found in Supplementary Table 1. ... Post-glacial eruptive history of SVZ and AVZ volcanoes, as known from the historical and geological record. Calendar age is given in years before 1950 AD (historical eruptions or varve-dated), ka (Ar-Ar or stratigraphically constrained), or ka cal BP for 14C ages. Uncalibrated 14C ages are given where available, and were calibrated in OxCal4.2 (Bronk Ramsey, 2009) using the SHCal13 calibration curve (Hogg et al., 2013). The most important eruptions are highlighted in blue; the large (V > 1 km3) eruptions for which dispersal data are available are highlighted in red. These eruptions are thought to have left significant regional marker horizons which should be readily identifiable in sediment sections. Numbered references can be found in Supplementary Information. ... Maps of a) south-central and b) southernmost Chile and Argentina, showing the locations of volcanoes (listed in Table 1) and the archeological and palaeoenvironmental records in which tephra has been recognised (listed in Supplementary Table 2), as well as the distributions of the tephra deposits from each post-glacial large (≥1 km3 tephra; VEI/M ≥ 5) explosive eruption (listed in Supplementary Table 1), and of some of the environments amenable to tephra unit preservation. The legend for Fig. 2a also applies to Fig. 2b. Coloured lines are isopach contours, indicating the area in which the deposits of an eruption are inferred to be ≥10 cm, unless an otherwise labelled (number of centimetres) dashed line. These data are from the articles cited for the corresponding eruptions in Supplementary Table 1; the source volcanoes of these eruptions are named. Tephra-bearing core/exposure location labels refer to reference numbers in Supplementary Table 2; only distal exposure locations are plotted. The geographical data are from Natural Earth (natrualearthdata.com), except the peatland extent, which is from Yu et al. (2010). ... Lake sediment core... Tephra occurrence in sediment sections from various environments. Unless a name was already given to a specific tephra horizon in literature, all tephra horizons are given a unique name consisting of the (abbreviated) core or location name followed by the central depth of the tephra in the sediment core. Numbered references can be found in Supplementary Information. ... Maps of a) south-central and b) southernmost Chile and Argentina, showing the locations of volcanoes (listed in Table 1) and the archeological and palaeoenvironmental records in which tephra has been recognised (listed in Supplementary Table 2), as well as the distributions of the tephra deposits from each post-glacial large (≥1 km3 tephra; VEI/M ≥ 5) explosive eruption (listed in Supplementary Table 1), and of some of the environments amenable to tephra unit preservation. The legend for Fig. 2a also applies to Fig. 2b. Coloured lines are isopach contours, indicating the area in which the deposits of an eruption are inferred to be ≥10 cm, unless an otherwise labelled (number of centimetres) dashed line. These data are from the articles cited for the corresponding eruptions in Supplementary Table 1; the source volcanoes of these eruptions are named. Tephra-bearing core/exposure location labels refer to reference numbers in Supplementary Table 2; only distal exposure locations are plotted. The geographical data are from Natural Earth (natrualearthdata.com), except the peatland extent, which is from Yu et al. (2010).... Peat core... Schematic representation of preservation environments for tephra in southern Chile and Argentina. Most preservation is restricted to vegetated areas (i.e., the Andes), lakes (6) and peatland (2). In addition to lake and peat cores, marine cores (1) can also provide important tephrostratigraphic records. Distal tephra deposits (5, 7) are easily eroded away due to prevailing westerly winds over the Argentine steppe. Strong winds may also result in complex dispersal patterns reflected in the architecture of the deposits (5, 7). Tephra in lakes may not always result from primary fallout, and can instead be remobilised into the lake from the river catchment (3, 4).
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  • Table of the identified tephra layers. Layers are labelled and the relative position (cmcd) in the composite core is indicated. The label (V) Corresponds to the volcaniclastic layer recorded in core C836. ... Correlation of the three studied cores with the constructed composite core. All the recognised tephra layers are labelled from tS1 to tS4-α; volcaniclastic layer is labelled V. Magnetic susceptibility values for cores C90 and C836 are from Iorio et al. (2004), for core C90-1m is from Vallefuoco et al. (2012). Core lithology of cores C90 and C836 are from Iorio et al. (2004) modified while C90-1m, is from Vallefuoco et al. (2012). ... Integrated eco-biostratigraphic scheme plotted vs time. The ages for the identified climatic events top Younger Dryas (at 11.50 ka BP), top TC6 (at 11.90 ka BP) and Sapropel S1 (base at 10.800 ± 0.400 ka BP and top at 6.100 ± 0.500 ka BP) are from Björck et al. (1998), Cacho et al. (2001) and De Lange et al. (2008), respectively, while age for the top of Bölling-Allerod (13.421 ± 0.175 ka BP) is from this work. The ages for the Mesolithic, Neolithic, Eneolithic, Early Bronze age, Middle Bronze age, Late Bronze age, Early Iron age, Greek colonian-Etrurian and Roman archeological periods are from Roberts et al. (2011). The ages for the Medieval Optimum and the Little Ice Age (LIA) are from Perry and Hsu (2000). The arrows represent the position of the identified tephra layers with the ages according to this work and according to literature data. ... Location map of the study area. a) The black rectangle is the study area, while the black circle (core GNS84-C106), the black triangle (core BS7939) and the black star (ODP-Site 963) represent the study cores of Di Donato et al. (2008), Sbaffi et al. (2004) and of Sprovieri et al. (2003), respectively, and used for correlation; b) detailed location map of the studied cores in the Salerno Gulf (C90-1m; C90, C836). ... 14C-AMS radiocarbon data available for the composite core.
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  • Pteropod shell preservation (LDX) in relation to the δ18O N. dutertrei record (Ivanochko et al., 2005) in core 905 off Somalia. Preservation spikes (low LDX values) occur during glacials and stadials. ... Comparison between carbonate dissolution proxies from different sites in the Indian Ocean. a) total abundance of pteropods per g of core KL15 (1631 m water depth; Almogi-Labin et al., 2000) from the Gulf of Aden; b) Composite Dissolution Index of core V34–53 (3812 m water depth) from the Ninety-East Ridge (after Peterson and Prell, 1985), higher values indicate better preservation; c) foraminiferal fragmentation index (fragments/(fragments+whole)) of core RC27–61 (1893 m water depth) from the Owen Ridge, northwestern Arabian Sea (after Murray and Prell, 1992); d) atmospheric CO2 concentrations from the Vostok ice core (after Petit et al., 1999), scale reversed for better comparison with the preservation records; e) relative abundance of whole pteropods (>125 μm) of core 905 off Somalia. ... Relative abundance of whole pteropods, whole pteropods including fragments in the coarse fraction (> 125 μm) in relation to the Corg content (Ivanochko et al., 2005) in core 905 off Somalia. Different pteropod preservation intervals are indicated by roman numbers. ... Late Quaternary... List of pteropod species found in the samples of core 905; + = abundant; ++ = common; − = rare; −− = very rare. ... Map showing the location of piston core 905 off Somalia.
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  • Alluvial sediments... 87Sr/86Sr and 143Nd/144Nd ratios in the silicate fraction of GS core sediments. ... δ13C (‰ VPDB) of bulk sediment organic matter from GS-10 and GS-11 cores. ... δ18O and δ13C of carbonate nodules from GS cores. Also given are sampling depths of host sediments containing the nodules. ... A–CN–K ternary plot (Nesbitt and Young, 1982) showing composition of GS-10 and GS-11 core sediments. Also shown for comparison are modern-river sediments from Himalaya (same as in Fig. 3), average values for world river sediments (Li and Yang, 2010), UCC, and PAAS. ... Temporal variations in (a and b) 87Sr/86Sr and εNd in GS core sediments; (c and d) δ18O and δ13C of carbonate nodules from GS cores; (e) δ13C of soil organic matter from GS cores; (f) Modeled record of change in the strength of SW Indian Monsoon from Prell and Kutzbach (1987); and (g) δ18O ice core record from the Guliya ice cap, Qinghai–Tibetan Plateau (Thompson et al., 1997). Also shown for comparison are 87Sr/86Sr and εNd in sediments (in a and b; Rahaman et al., 2009), and δ18O and δ13C values of carbonate nodules (in c and d; Rahaman et al., 2011) in a ~50m core from the Ganga interfluves.
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  • Depth distribution of pH, EC, CaCO3, OC, particle size distribution and textural class of the Bhognipur core. ... The XRD analysis of core sediments from IITK core shows dominance of mica in the silt (50–2μm) and coarse clay (2–0.2μm) fractions that also contain mixed-layer minerals, smectite, vermiculite, HIV, PCh, kaolin, feldspar and quartz (see Figs. 1–3 in the supplementary material). The fine clay fractions (<0.2μm) are dominated by mica and smectite along with vermiculite, HIV, PCh and kaolin. The smectite is predominantly LCS and dioctahedral in nature in fine clay fraction but silt and coarse clay fractions are dominantly HCS. The collapsing characteristics of K-saturated fine clay on heating from 110°C to 550°C indicate that most of the LCS has hydroxy-interlayering (Harward et al., 1969).... Identification key for the clay minerals in IITK and Bhognipur cores, Ganga–Yamuna interfluve, India. ... (a) Stratigraphy and paleosol distribution of the IITK drill core. A total of 4 major stratigraphic units and 13 paleosols were identified in this core covering a time span of ~100ka. The entire core is dominated by muddy sediments with thin silt layers at regular intervals. (b) Stratigraphy and paleosol distribution of the Bhognipur drill core. A total of 6 major stratigraphic units and 10 paleosols were identified in this core. This entire core is distinctly coarser in the lower parts with >10m sand body representing a major channel. ... Depth distribution of pH, EC, CaCO3, OC, particle size distribution and textural class of the IITK core. ... Study area in the Ganga–Yamuna interfluve (GYI) showing drill core at Indian Institute of Technology, Kanpur (IIT, K) and Bhognipur, Kalpi (BHOG, K).
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  • Lithology, shear strength, clay mineral content and facies types of the studied sediment cores that have not been presented in Fig. 3. ... Average clay mineral composition of sediments in the lower lithological unit of the studied cores. ... Average clay mineral composition of sediments in the upper lithological unit of the studied cores. ... Map of the southern Bellingshausen Sea with locations of sediment cores and surface sediment samples (note: only identifications of gravity core sites are given, for a summary of all locations see Supplementary Table). Grounded ice-flow directions according to Ó Cofaigh et al. (2005a). ... Average clay mineral composition of sediments in the middle lithological unit of the studied cores. ... Late Quaternary
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