A LESS HUMID CLIMATE SINCE CA.3500-YR-BP FROM MARINE CORES OFF KARWAR, WESTERN INDIA

A marked change in the vegetation of the Western Ghats at ca. 3500 yr B.P. has been observed from a study of two marine cores taken from the inner shelf off Karwar (Karnataka, western India), at the mouth of th e Kalinadi River. This change is indicated by a decrease in forest pol len, particularly from evergreen forests and by a corresponding increa se in savanna pollen, as well as by a reduction in mangrove pollen. At the same time, the values of the stable isotope deltaC-13 of sediment ary organic matter increased suddenly due to a higher contribution of organic matter of marine origin. All these modifications were probably induced by a less humid climate (the term ''drier'' can hardly be use d for an area where the annual rainfall still attains 6 m in the hills ). Above this clear limit, the same trends (steady but considerably we aker), also resulting from a reduction in the humid conditions, were r ecorded up to ca. 2200 yr B.P.: reduction in forests vs. increase in s avannas; decrease in the mangrove vegetation; higher deltaC-13 values. From there onwards the pollen assemblages have remained uniform up to the present day. It may be deduced that a climate quite similar to th e present conditions was established about 2200 yr ago, and still prev ails. The curves representing the percentages of marine microfossils-d inoflagellates, organic tests of foraminifera, eggs of copepods-show l ittle variation at the 3500 yr B.P. boundary. The marine assemblages w ere modified drastically only at about 2200 yr B.P. These sharp modifi cations are probably due to an increase in the marine influence as a r esult of a reduction in the fresh water supply from the Kalinadi. The stability in the representation of marine assemblages which has persis ted from about 2200 yr B.P. to the present confirms the establishment of the present-day climate around that date. This paleoclimatic recons truction is in conformity with the evidence for the beginning of drier conditions recorded at about the same time in the low latitudes in ma ny parts of the world: India, northern Arabian Sea, Africa (Sahara, tr opical forests, East African lakes), Australia and the Carribbean.