Evidence of increased rainfall prior to 3500 years BP as revealed by river borne terrigenous flux: A study from west coast of India

The study has been conducted for insoluble residue and Calcium Carbonate content in a 4.80 m long shallow water (at 22 m water depth) sediment core (at 22 m water depth) off Central West Coast of India to reconstruct palaeo monsoonal precipitation linked with river discharge. The down core profile of carbonate content shows that it is generally less than 28% below ca. 3.00 m whereas, above 3.00 m it is generally more than 28% and this showing an general upward trend. On the contrary, the average insoluble residue is marked by higher value (>72%) below ca. 3.00 m while, above 3.00 m it is low (<72%) and showing a general downward trend. These trends ostensibly suggest an increased rainfall prior to around 3500 year BP which resulted in enhanced river discharge along with insoluble residue and diminution of calcium carbonate, (ascribed due to reduced productivity). Such a distinct response of Calcium Carbonate and insoluble residue at 3.00 m, corresponding to around 3500 years BP is congruous with the already established climatic changes of this core at ca. 3500 years BP linked with salinity changes due to alteration of rainfall pattern.