Publication Date:
2020-02-24
Description:
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
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.
Description:
Published
Description:
2093–2109
Description:
1A. Geomagnetismo e Paleomagnetismo
Description:
JCR Journal
Description:
open
Keywords:
Environmental magnetism Pleistocene Lake Ohrid
;
04. Solid Earth::04.05. Geomagnetism::04.05.09. Environmental magnetism
Repository Name:
Istituto Nazionale di Geofisica e Vulcanologia (INGV)
Type:
article
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