Change in provenance of branched glycerol dialkyl glycerol tetraethers over the Holocene in the Baltic Sea and its impact on continental climate reconstruction
Warden, L.; Moros, M.; Weber, Y.; Sinninghe Damsté, J.S (2018). Change in provenance of branched glycerol dialkyl glycerol tetraethers over the Holocene in the Baltic Sea and its impact on continental climate reconstruction. Org. Geochem. 121: 138-154. https://doi.org/10.1016/j.orggeochem.2018.03.007
In: Organic Geochemistry. Elsevier: Oxford; New York. ISSN 0146-6380; e-ISSN 1873-5290, meer
The Baltic Sea is an enclosed basin that experienced a number of different salinity phases during theHolocene corresponding to the establishment of a connection with the North Sea. Branched glyceroldialkyl glycerol tetraethers (brGDGTs) in surface sediments and Holocene sedimentary successions fromthe Gotland and Arkona Basins were analyzed to examine their potential applicability as indicators forsoil organic matter input, as well as their suitability for paleoclimate reconstructions. Our results showa marked change in brGDGT distributions and the branched and isoprenoid tetraether (BIT) index. Thetransition of the Ancylus Lake (fresh) to the Littorina Sea (brackish) phase is revealed by a large dropin the BIT index and an increase in the MBT05Me, which reveals a large shift in provenance of the sedimentarybrGDGTs. During the lake phase, brGDGTs are presumed to be primarily produced by in situ productionin the water column. During the brackish phase, in situ brGDGT production in the alkaline porewaters of the surface sediments (as revealed by their high degree of cyclization) was predominantalthough there was evidence of occasional input of soil-derived brGDGTs. The predominant aquatic autochthonousproduction of brGDGTs does not allow the use of brGDGTs for continental air temperaturereconstructions but they can be used for bottom water and lake temperature reconstructions duringsome intervals. The results from this study demonstrate that geological changes and concomittant salinityvariations can be revealed by the provenance of brGDGTs.
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