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Abstracts / Quaternary International 279-280 (2012) 462–565
NATURAL AND ANTHROPOGENIC TRACE ELEMENTS RECORDS FROM LOW AND HIGH ALTITUDES SWISS LAKES Florian Thevenon. University of Geneva, Switzerland E-mail address:
[email protected]
Continuous records of trace elements from two large European freshwater lakes located on the Swiss Plateau (Geneva and Lucerne) and from a highaltitude remote lake from the Southern Alps (Meidsee), show that in absence of significant human disturbances, the trace element input is primarily controlled by the sedimentological response to natural hydrological changes. In this context, the heavy metals distribution is similar to that of the geogenic elements, which is primarily influenced by changes in sediment composition and texture due to increased chemical (runoff) or physical (erosion) weathering processes. In fact, the deposition of trace elements remains close to the range of natural variations until the strong impact of Roman activities on atmospheric metal emissions. Lake Lucerne and Meidsee exhibit simultaneous increases in anthropogenic trace metal deposition during the Greek and Roman Empires, the Late Middle Ages, and the Early Modern Europe. However, the greatest increases in anthropogenic metal pollution are evidenced at all sites after the industrial revolution of ca. AD 1850. Lakes Lucerne and Geneva document maximum levels of pollution in Switzerland during the twentieth century, especially during the 1960s, when large freshwater lakes became eutrophic. Anthropogenic heavy metal inputs subsequently stopped increasing thanks to environmental protection and domestic regulations in the 1970s, whereas the absence of a decreasing trend in sedimentary phosphorus suggests a delayed response of the hypolimnion (internal P supplies linked to the decomposition of the sediments that accumulated during the anoxic period), and reduced deep water mixing linked to warmer climate impact on lake's water-temperature profiles. RECENT METHODOLOGICAL DEVELOPMENTS IN PALEORECORDS OF COMBUSTION FROM DIFFERENT DEPOSITIONAL ENVIRONMENTS (OCEAN, LAKE, AND GLACIER) Florian Thevenon. University of Geneva, Switzerland E-mail address:
[email protected]
This review addresses an overview of records of combustion from various climatic archives through recent methodological developments. The pyrogenic carbon records are based on i) the automated image analysis for quantifying charcoal flux and morphology, ii) the elemental black carbon and its isotopic composition, and iii) the trace element analysis to identify anthropogenic heavy metal inputs. The data show that the redistribution of fossil particles by runoff and erosion processes is a significant source of pyrogenic carbon and trace elements that should be understood as a prerequisite for interpreting sedimentary records of combustion. The burial of dark carbon-rich particles in the 360 kyr-long record from the west equatorial Pacific is controlled by the combination of sea-level changes and low-latitude atmospheric circulation patterns; whereas major shifts in fire activity occur synchronously with human colonization in the Indo/Pacific region. The coarse charcoal distribution from Lake Lucerne record (Switzerland) closely matches the regional timing of major technical, landuse, and socio-economic changes since the Neolithic. In the tropical Masoko maar lake (Tanzania), charcoal and BC exhibit a major increase synchronously with the regional extent of Late Iron Age and agricultural innovations. The image analysis method evidences increase in the length/width ratio of the charcoal associated to changes in the vegetation, and black spherical fly-ash particles linked to fossil fuel combustion. Finally, the d13CBC record from the Alpine ice core shows that wood combustion largely dominates European preindustrial atmospheric BC emissions.
NEW CHRONOSTRATIGRAPHIC RESULTS FOR LOWER AUSTRIAN LOESS/ PALAEOSOL SEQUENCES Christine Thiel. Leibniz Institute for Applied Geophysics, Germany E-mail address:
[email protected]
Loess/palaeosol sequences are detailed archives for terrestrial palaeoenvironmental changes and landscape evolution. Unfortunately, most
loess sequences lack a reliable absolute chronology and hence the landscape changes are difficult to constrain in time. Radiocarbon and luminescence dating have been used to establish chronologies for the Late Pleistocene, whereas for Middle Pleistocene loess deposits there has been no generally applicable and reliable instrumental dating method. Only recently, new luminescence dating techniques such as post-IR infrared stimulated luminescence (IRSL) opened the opportunity to accurately date Middle Pleistocene sediments. We present an overview of post-IR IRSL dating results which were obtained for several well-known Lower Austrian loess/palaeosol sequences such as Paudorf, Göttweig and Stratzing. The Paudorf soil (‘Paudorfer Bodenbildung’) can be correlated to marine isotope stage (MIS) 5, and the Göttweig soil (‘Göttweiger Verlehmungszone’) is at least 300 ka (MIS 9). The new data sets are compared with formerly published chronostratigraphies and are discussed with respect to the limitations of dating methods. THE POTENTIAL OF LUMINESCENCE DATING FOR AGE DETERMINATION OF ANCIENT DNA EXTRACTED FROM SILTY ICE Christine Thiel. Leibniz Institute for Applied Geophysics, Germany E-mail address:
[email protected]
The Camp Century Ice Core from Greenland has provided plant DNA sequence data from different depths; these describe the palaeoenvironment prior to the development of the ice sheet. However, the age of this vegetation and of the formation of the ice is unknown. To develop such a chronological framework, individual sediment grains dispersed in the ice at different depths close to the base of the ice sheet were collected for dating using luminescence. Using an elevated temperature post-IR infrared stimulated luminescence (IRSL) protocol we measured the burial dose recorded by individual 90-180 mm grains. A dose recovery measurement showed that our protocol is applicable to these grains. During handling of the ice core after drilling and subsequent cutting, the frozen samples were exposed to fluorescent light. To evaluate the resulting signal loss, we exposed feldspar grains to similar laboratory lighting and measured the remaining signal. From the differential bleaching rates of the two IRSL signals we conclude that the samples were probably exposed to 2-4 hours room lighting, easily consistent with the independent estimate of
