Coastal Aeolianite Deposits: an Archive of Indian Monsoon Rainfall and Winds over the Late Quaternary

Abstract

Coastal aeolianites occur throughout the world both in the Sub-Tropical and Extra- Tropical regions and act as valuable repositories of both past climate changes due to their sensitivity to meteoric diagenesis. Palaeowind directions (northeast to north northeast) based on measurements of these Cross-Beds suggest that the formative winds were the Indian summer monsoon winds. Stratigraphic and architectural analyses reveal that the coastal aeolianite deposits (Miliolite)have three Terra Rossa type soils over the past ∼200 ka. This points to the fact that coastal aeolianites respond sensitivity to the changing intensities of the Indian monsoon rainfall. Periods of increased rainfall led to weathering which eventually formed Terra Rossa like soil while prolonged periods of reduced rainfall but strong winds led to the formation of parabolic dunes. As strong monsoon winds are required both for precrpitation and wind transport, this suggests, that the Indian summer monsoon winds were strong and intense throughout the past -200 ka. These results validate recent results from a coupled Ocean-Atmosphere GCM that predict stronger summer monsoon winds during glacial periods.