Late Quaternary Continental Studies in Parts of India: Implications for Monsoon Variability

Indian Summer Monsoon (ISM) is the major climatic feature in the Indian sub continent. Since marine proxies used for monsoon reconstructions are the expressions of the wind strength that may or may not translate on land as rainfall, the continental records are the direct proxies of rainfall variability. We have made an attempt here to synthesize the available works aimed at past monsoon reconstruction using the chronologically constrained continental archives. The nature of geomorphic response of a fluvial system depends upon its environmental setting and the magnitude and duration of a climatic perturbation. In the present synthesis it was observed that events that lasted for ∼10⁴ years could imprint its signature particularly in the fluvial systems irrespective of their geographical location. Except few examples, there is virtually no evidence of short term climatic fluctuations coming out from the available fluvrial records. Could it be due to the fact that short lived climate instability (10² to 10³ years) are not sufficient enough to bring about major geomorphic changes in fluvial processes?

Climatic inferences drawn so far using the fluvial and aeolian archives are largely based on the field stratigraphy, sedimentology and chronometric studies from limited geographical areas. There is a need for wider coverage pertaining to the fluvial systems particularly in the peninsular and southern Indian rivers. Further, unless, the clitmate proxies like stable isotopes, geochemistry, and environmental magnetism are used the monsoonal inferences would remain qualitative. Lacustrine sequences provide uninterrupted record of monsoonal variability. This important continental archive has not been exploited to its potential, except for the Thar Desert Renewed efforts should be made to explore other areas including the Himalaya.