A 1-million-year record of environmental change in the Central Mediterranean Sea from organic molecular proxies

Martínez-Dios, A.; Pelejero, C.; Cobacho, S.; Movilla, J.; Dinarès-Turell, J.; Calvo, E.
Paleoceanography and Paleoclimatology
The Mediterranean Sea is particularly sensitive to climate oscillations and represents a key location to study past climatic and oceanographic changes. One valuable source of paleoceanographic information is through molecular biomarkers in deep sea sediments. This approach has been applied in a number of studies in this basin, but only covering the most recent glacial/interglacial cycles. Here we present, for the first time in the Mediterranean Sea, a molecular biomarker record from the Strait of Sicily that covers the last million years until the present, almost continuously. We present data on alkenone derived UK’37 index sea surface temperatures (SST) and provide insights on the evolution of the phytoplankton community composition and terrestrial inputs through the analysis of the concentrations of alkenones, brassicasterol and long-chain alcohols. The UK’37 -SST record followed a climatic evolution modulated by glacial/interglacial cycles with a marked increase in the 100 kyr-amplitude of the glacial cycles at ∼430 ka, coincident with the Mid-Brunhes transition. In addition, SSTs were consistently higher compared with other records in the western Mediterranean, indicative of the progressive warming that surface waters experience along their transit from the Strait of Gibraltar to the Central Mediterranean. Regarding the concentrations of alkenones and brassicasterol, they displayed distinct alternate peaks, some of them coeval with the deposition of sapropels. This suggests that different environmental and oceanographic conditions characterized each sapropel which, together with changes in terrestrial inputs and the degree of oligotrophy, induced the alternate proliferation of coccolithophores and diatoms.
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