Browsing by Author "Klootwijk, C"

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    An improved radiocarbon chronology and calibration over the Laschamp event: 14C – 10Be cross synchronisation
    (Geological Society of Australia, 2010-07-04) Levchenko, VA; Opdyke, BN; Fink, D; Mifsud, C; Williams, AG; Klootwijk, C
    The production rate of cosmogenic isotopes 10Be and 14C is influenced by variations in the primary cosmic ray flux and by changes of the Earth’s magnetic field, which has experienced a number of significant perturbations during the late Quaternary (e.g. Lashamp/Mono Lake excursion, circa 41 ka BP). Understanding these changes and synchronising variations in palaeomagnetic intensity derived from various marine sediment cores can often help constrain the quality of 14C dating, particularly in the interval between 20 and 50 ka ago, and establish reliable chronologies for ocean sedimentation rate changes. A common often used proxy for these palaeomagnetic changes is atmospheric fallout of 10Be in marine sediments. We are investigating the Core MD – 982167, which was recovered from the Scott Plateau in the Eastern Indian Ocean at latitude of 13°S. The MD‐982167 already has an established stable isotope stratigraphy and a high sedimentation rate of 10 to 20 cm per ka. A series of 14C and 10Be determinations in foramifera and fine fraction of the core sediments as a function of core depth have been obtained. Palaeomagnetic measurements with the aim to determine the position of geomagnetic disturbances like Laschamp and Mono Lake as recorded in the ocean sediments were also done on the samples from the same core. Synchronisation of palaeomagnetic, 10Be and radiocarbon records together with the application of 10Be pulse as a global chronostratigrafic marker is discussed. An improved chronology for this high resolution core that has recorded brief, less than one thousand year duration, climatic events during the studied time interval will allow much better correlation between marine sedimentary records and the detailed chronologies established from the ice cores.
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    An improved radiocarbon chronology for MD-982167, eastern Indian Ocean: synchronizing paleomagnetic intensity and 10Be across the Laschamp event
    (20th International Radiocarbon Conference, 2009-06-02) Levchenko, VA; Fink, D; Opdyke, BN; Mifsud, C; Williams, AG; Klootwijk, C
    The production rate of cosmogenic isotopes 10Be and 14C is influenced by variations in the primary cosmic-ray flux and by changes of the Earth’s magnetic field, which has experienced a number of significant perturbations during the late Quaternary (e.g. Laschamp excursion, ca. 41 kyr BP). Understanding these changes and synchronizing variations in paleomagnetic intensity derived from various marine sediment cores can often help constrain the quality of 14C dating, particularly for times beyond IntCal04 between 30 and 50 kyr ago, leading to improved overall core chronologies and determination of ocean sedimentation rates. An often used proxy for these paleomagnetic changes is the concentration of atmospheric fallout of 10Be in marine sediments. The ocean core MD-982167 recovered from the Scott Plateau in the eastern Indian Ocean (13°09′S, 121°35′E; depth of 1981m) has an established δ18O stable isotope stratigraphy and a high sedimentation rate of 10 to 20 cm/kyr based on a preliminary chronology tied to ice-core records. This in turn makes MD-982167 amenable to high-resolution 10Be assay across the Laschamp period. We have completed measurements of 10Be and 14C (in both foraminifera and fine sediments) and paleomagnetic intensity in core MD-982167. We are able to correlate variations in 10Be with paleomagnetic intensity recorded in these ocean sediments based on our detailed radiocarbon age-depth profile and confirm a strong presence of the Laschamp excursion at 39.9 ± 1.3 kyr BP. Comparing the variations of atmospheric-derived 10Be in MD-982167 tied to our improved radiocarbon chronology with 10Be established from the ice cores and will allow much better correlation between marine sedimentary and ice-core records across recent stadial and interstadial climatic events.