Single-Grain Zircon U-Pb Dating and Magnetic Susceptibility of Polish Loess to Determine Late Quaternary Dust Provenance and Paleoclimate

• Main Author: Engström Johansson, Alexandra
• Format: Bachelor Thesis
• Language: English
• Published: Uppsala universitet, Institutionen för geovetenskaper 2018
• Subjects: dust provenance; Polish loess; paleoclimate; single-grain zircon U-Pb dating; magnetic susceptibility; härkomstområden för atmosfäriskt stoft; polsk lössjord; paleoklimat; U-Pb datering av zirkoner; magnetisk susceptibilitet; Geochemistry; Geokemi; Damm; Fennoscandia
• Online Access: http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-364540

Windblown mineral dust has accumulated into thick loess layers across the European continent. Loess deposits are valuable paleoclimatic archives as they record climate change on centennial- to glacialinterglacial timescales. A reliable identification of dust sources is of fundamental importance for paleoclimatic reconstructions of atmospheric circulation patterns and dust pathways, and for understanding the link between mechanisms of dust production and -emissions and climate change. European dust sources are however still relatively poorly constrained, which in part is related to the few provenance studies performed using single-grain techniques. Single-grain techniques, and in particular single-grain U-Pb dating of detrital zircons, may allow for a reliable identification of multiple individual sources, as has been shown for the Chinese loess archive. Few dust provenance studies in general, and none found using single-grain techniques, have been performed on Polish loess samples. The location of Polish loess deposits in the central parts of the European continent may allow for a more complete paleoclimatic picture by tying together provenance studies from west to east, as well as for distinguishing between the proposed central European dust source areas of distal Fennoscandia and the proximal mountains of Moravia, the Alps, the Sudetes, the Bohemian Massif and the Carpathians. Forty-two loess samples were collected from the Biały Kościół loess profile in southwestern Poland, spanning deposition ages from the Eemian to the Holocene (MIS 5-1). Five samples were dated using single-grain zircon U-Pb geochronology and thirty-seven samples were measured and analysed using magnetic parameters of mass-specific-, frequency- and phase dependent susceptibility which reflect changes in mineralogy and grain size of magnetic mineral fractions. Magnetic susceptibility results show variations between and within stratigraphic units. Different soil formation processes appear to have been dominant during the three paleosol units ...