Branched glycerol dialkyl glycerol tetraethers and crenarchaeol record post-glacial sea level rise and shift in source of terrigenous brGDGTs in the Kara Sea (Arctic Ocean)
de Jonge, C.; Stadnitskaia, Alina; Cherkashov, G.; Sinninghe Damsté, J.S. (2016). Branched glycerol dialkyl glycerol tetraethers and crenarchaeol record post-glacial sea level rise and shift in source of terrigenous brGDGTs in the Kara Sea (Arctic Ocean). Org. Geochem. 92: 42-54. dx.doi.org/10.1016/j.orggeochem.2015.11.009
In: Organic Geochemistry. Elsevier: Oxford; New York. ISSN 0146-6380; e-ISSN 1873-5290, meer
This study evaluates the glycerol dialkyl glycerol tetraether (GDGT) distribution and provenance in sediments(spanning a minimum of 13.3 ka) from the St. Anna Trough (Northern Kara Sea). The site has experiencedextensive fluctuation in the delivery of river-derived organic matter (OM), caused by a eustaticchange in sea level. This is in line with the record of the concentration of the isoprenoid GDGT, crenarchaeol,produced by marine Thaumarchaota, which was low at the bottom of the core, increasing graduallyin the most shallow unit. The concentration of branched (br)GDGTs showed an opposite trend and amarked shift in distribution. The deepest sediments (>10 ka), with a distribution currently encounteredin surface sediments in front of the Yenisei River, are characterized by terrigenous brGDGTs, whereas thedistribution in the shallowest unit (<10 ka) is strongly influenced by marine, in-situ brGDGTs. During theshift from terrigenous to marine-sourced brGDGTs, there was one horizon where a pronounced shift inthe brGDGT distribution was observed and the brGDGT concentration significantly decreased. As thebrGDGTs delivered to the current Kara Sea system are derived from several sources, we postulate thata temporary change in the relative importance of the brGDGT sources happened during this interval.Both in-situ production and changing brGDGT provenance have implications for paleoclimate reconstructionusing brGDGTs. In-situ production of marine brGDGTs results in a higher reconstructed pH. However,these in-situ produced brGDGTs did not influence the reconstructed mean annual air temperature (MAT),when the MATmrs calibration was used. Changes in the relative contribution of brGDGT sub-pools wereshown, however, to influence both soil pH reconstruction and MAT reconstruction.
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