Multi-domain magnetic particles in speleothems as a proxy for past cave-stream flooding: A 33 kyr record from central North Island, Aotearoa New Zealand
Bethany R.S. Fox , Ioan Lascu , Richard Harrison , Andrew R. Pearson , John Hellstrom , Sebastian F.M. Breitenbach , Joshua F. Einsle , Joy Muraszko , Adam Hartland
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引用次数: 0
Abstract
Speleothems are a key archive for past terrestrial climate information due to their potential for long, continuous, high-resolution, precisely-dated proxy records. The concentration and grain-size distribution of allogenic magnetic minerals incorporated into speleothems can be used to reconstruct past hydrological regimes. We use principal component analysis of first-order reversal curves to characterise the magnetic minerals incorporated into a 33 kyr flowstone record from Aotearoa New Zealand. Three end members (EMs) represent (1) a component with a broad spectrum of grain sizes, similar to that found in the overlying soil (EM1); (2) a coarse multi-domain component, with grains ranging up to several hundred microns (EM2); and (3) a fine, single-domain to vortex component (EM3). We interpret EM1 and especially EM2 as proxies for cave stream flooding and EM3 as a proxy for soil erodibility and transport through infiltration or possibly aeolian processes. We find increased soil erodibility during the period 30-20 kyr BP, corresponding to the extended Last Glacial Maximum (eLGM). Flooding frequency is high during the periods 27-25 kyr BP and 9-0 kyr BP. eLGM flooding episodes as recorded in the flowstone may be enhanced by the deposition of the Kawakawa/Oruanui tephra, providing a rich source of magnetic material. This study shows the potential for coarse, multi-domain magnetic material incorporated in speleothems as a source of palaeoenvironmental information, especially in regions characterised by magnetite-rich soils and frequent, high-energy hydrologic events.
期刊介绍:
Quaternary Science Reviews caters for all aspects of Quaternary science, and includes, for example, geology, geomorphology, geography, archaeology, soil science, palaeobotany, palaeontology, palaeoclimatology and the full range of applicable dating methods. The dividing line between what constitutes the review paper and one which contains new original data is not easy to establish, so QSR also publishes papers with new data especially if these perform a review function. All the Quaternary sciences are changing rapidly and subject to re-evaluation as the pace of discovery quickens; thus the diverse but comprehensive role of Quaternary Science Reviews keeps readers abreast of the wider issues relating to new developments in the field.