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)

نویسندگان

  • Janna Just
  • Norbert R. Nowaczyk
  • Leonardo Sagnotti
  • Alexander Francke
  • Hendrik Vogel
  • Jack H. Lacey
  • Bernd Wagner
چکیده

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 highto 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.

برای دانلود متن کامل این مقاله و بیش از 32 میلیون مقاله دیگر ابتدا ثبت نام کنید

ثبت نام

اگر عضو سایت هستید لطفا وارد حساب کاربری خود شوید

منابع مشابه

Interactive comment on “Climatic control on the occurrence of high-coercivity magnetic minerals and preservation of greigite in a 640 ka sediment sequence from Lake Ohrid (Balkans)” by J. Just et al

This manuscript details magnetic mineral measurements from the sediments of Lake Ohrid, which serves as proxies for paleoenvironmental and paleoclimatic change. The new cores from Lake Ohrid comprise one of the longest continuous records from Europe, and the analyses and submission advance our understanding of the regional glacial-interglacial climate and environmental history. In particular, t...

متن کامل

Interactive comment on “Climatic control on the occurrence of high-coercivity magnetic minerals and preservation of greigite in a 640 ka sediment sequence from Lake Ohrid (Balkans)” by J. Just et al

This manuscript details magnetic mineral measurements from the sediments of Lake Ohrid, which serves as proxies for paleoenvironmental and paleoclimatic change. The new cores from Lake Ohrid comprise one of the longest continuous records from Europe, and the analyses and submission advance our understanding of the regional glacial-interglacial climate and environmental history. In particular, t...

متن کامل

Interactive comment on “Climatic control on the occurrence of high-coercivity magnetic minerals and preservation of greigite in a 640 ka sediment sequence from Lake Ohrid (Balkans)” by J. Just et al

The Just et al. manuscript relies on four other manuscripts that are currently also in review in Biogeosciences (Baumgarten et al., 2015; Francke et al., 2015; Leicher et al., 2015; Sadori et al., 2015). Consequently, in order to evaluate the manuscript in terms of scientific content, I have read through many manuscripts. This was time consuming, but I applaud the fact that all Lake Ohrid manus...

متن کامل

Reconstruction of the Late-Quaternary climate change using magnetic susceptibility of Saadabad-Gorgan loess deposits

Introduction   One of the processes of the Quaternary era is the glacial and interglacial periods. In the glacial period, loesses deposited and in the interglacial period, Paleosoils were formed. The northern part of Iran is geographically the same as countries such as China, a large part of which has been covered with loess sediments during the Pleistocene glacial period. Loess sediments in ...

متن کامل

Northern Mediterranean climate since the Middle Pleistocene: a 637 ka stable isotope record from Lake Ohrid (Albania/Macedonia)

Lake Ohrid (Macedonia/Albania) is an ancient lake with unique biodiversity and a site of global significance for investigating the influence of climate, geological, and tectonic events on the generation of endemic populations. Here, we present oxygen (δO) and carbon (δC) isotope data from carbonate over the upper 243 m of a composite core profile recovered as part of the Scientific Collaboratio...

متن کامل

ذخیره در منابع من


  با ذخیره ی این منبع در منابع من، دسترسی به آن را برای استفاده های بعدی آسان تر کنید

برای دانلود متن کامل این مقاله و بیش از 32 میلیون مقاله دیگر ابتدا ثبت نام کنید

ثبت نام

اگر عضو سایت هستید لطفا وارد حساب کاربری خود شوید

عنوان ژورنال:

دوره   شماره 

صفحات  -

تاریخ انتشار 2016