Universität zu Köln

Just, Janna ORCID: 0000-0002-5257-604X, Nowaczyk, Norbert R., Sagnotti, Leonardo ORCID: 0000-0003-3944-201X, Francke, Alexander ORCID: 0000-0002-0370-5802, Vogel, Hendrik ORCID: 0000-0002-9902-8120, Lacey, Jack H. ORCID: 0000-0002-6329-2149 and Wagner, Bernd ORCID: 0000-0002-1369-7893 (2016). Environmental control on the occurrence of high-coercivity magnetic minerals and formation of iron sulfides in a 640 ka sediment sequence from Lake Ohrid (Balkans). Biogeosciences, 13 (7). S. 2093 - 2110. GOTTINGEN: COPERNICUS GESELLSCHAFT MBH. ISSN 1726-4189

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Abstract

The bulk magnetic mineral record from Lake Ohrid, spanning the past 637 kyr, reflects large-scale shifts in hydrological conditions, and, superimposed, a strong signal of environmental conditions on glacial-interglacial and millennial timescales. A shift in the formation of early diagenetic ferrimagnetic iron sulfides to siderites is observed around 320 ka. This change is probably associated with variable availability of sulfide in the pore water. We propose that sulfate concentrations were significantly higher before similar to 320 ka, due to either a higher sulfate flux or lower dilution of lake sulfate due to a smaller water volume. Diagenetic iron minerals appear more abundant during glacials, which are generally characterized by higher Fe/Ca ratios in the sediments. While in the lower part of the core the ferrimagnetic sulfide signal overprints the primary detrital magnetic signal, the upper part of the core is dominated by variable proportions of high-to low-coercivity iron oxides. Glacial sediments are characterized by high concentration of high-coercivity magnetic minerals (hematite, goethite), which relate to enhanced erosion of soils that had formed during preceding interglacials. Superimposed on the glacial-interglacial behavior are millennial-scale oscillations in the magnetic mineral composition that parallel variations in summer insolation. Like the processes on glacial-interglacial timescales, low summer insolation and a retreat in vegetation resulted in enhanced erosion of soil material. Our study highlights that rock-magnetic studies, in concert with geochemical and sedimentological investigations, provide a multi-level contribution to environmental reconstructions, since the magnetic properties can mirror both environmental conditions on land and intra-lake processes.

Item Type:	Journal Article
Creators:	Creators Email ORCID ORCID Put Code Just, Janna UNSPECIFIED orcid.org/0000-0002-5257-604X UNSPECIFIED Nowaczyk, Norbert R. UNSPECIFIED UNSPECIFIED UNSPECIFIED Sagnotti, Leonardo UNSPECIFIED orcid.org/0000-0003-3944-201X UNSPECIFIED Francke, Alexander UNSPECIFIED orcid.org/0000-0002-0370-5802 UNSPECIFIED Vogel, Hendrik UNSPECIFIED orcid.org/0000-0002-9902-8120 UNSPECIFIED Lacey, Jack H. UNSPECIFIED orcid.org/0000-0002-6329-2149 UNSPECIFIED Wagner, Bernd UNSPECIFIED orcid.org/0000-0002-1369-7893 UNSPECIFIED
URN:	urn:nbn:de:hbz:38-292354
DOI:	10.5194/bg-13-2093-2016
Journal or Publication Title:	Biogeosciences
Volume:	13
Number:	7
Page Range:	S. 2093 - 2110
Date:	2016
Publisher:	COPERNICUS GESELLSCHAFT MBH
Place of Publication:	GOTTINGEN
ISSN:	1726-4189
Language:	English
Faculty:	Unspecified
Divisions:	Unspecified
Subjects:	no entry
Uncontrolled Keywords:	Keywords Language LATE DIAGENETIC GROWTH; GREIGITE FE3S4; BACTERIAL MAGNETITE; REMANENCE CURVES; ROCK MAGNETISM; CHINESE LOESS; RECORD; CLIMATE; SEA; VARIABILITY Multiple languages Ecology; Geosciences, Multidisciplinary Multiple languages
Refereed:	Yes
URI:	http://kups.ub.uni-koeln.de/id/eprint/29235