Climate control on allochthonous sedimentation in the deep sea

Abstract

Four giant piston cores from the Balearic Abyssal Plain have been studied in detail in order to broadly quantify the differences in advective sediment flux to the Balearic Abyssal Plain (the western Mediterranean Sea) over the last glacial/interglacial cycle.  The cored Balearic Abyssal Plain sedimentary sequence (30-35 m) is dominated by turbidite deposits (90%).  Intercalated hemipelagic intervals, which only make up 10% of the recovered sedimentary sequence, were used to form a tight stratigraphic framework that has been fine-tuned to the GISP2 ice core record from Greenland.  This stratigraphic framework provided important constraints on individual turbidite emplacement times.  Turbidite deposition on the Balearic Abyssal Plain occurred regularly and without major temporal gaps, with an average frequency of one turbidite every one to two thousand years.  The highest number of turbidites occurred during periods of maximum sea-level (and climate) change.  Turbidite beds from the last glacial period (Marine Isotope Stages 2-4) are much thicker than turbidite beds emplaced during interglacial periods (Marine Isotope Stages 1 and 5), which suggests that the glacial advective sediment flux to the Balearic Abyssal Plain was significantly enhanced.  Sediment supply to the margins and the Balearic Abyssal Plain is estimated to have been least doubled during the last glacial maximum, due to increased riverine sediment fluxes.  Turbidite frequencies (number/ka) were also enhanced during Marine Isotope Stage 1, which is explained by anthropogenic deforestation and the subsequent increase in erosion during this period.  The results presented indicate that the temporally well-constrained data do not support the hypothesis that the advective sediment flux to the basin is only high during glacials - this view is too simple and does not stand up to detailed testing.

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