A 30 KA SUMMER MONSOON DRIVEN TERRESTRIAL RAINFALL VARIABILITY RECORD FROM CENTRAL HIGHLANDS OF SRI LANKA

A 30 ka summer monsoon driven terrestrial rainfall variability record from Central Highlands of Sri Lanka reveals a clear correlation with high-latitude northern hemisphere climate. Sri Pada mountain range (Adam’s Peak) situated at the southwestern corner of the Central Highlands of Sri Lanka receives rainfall mainly from summer monsoon. Wetland covered Gawaratenna plateau, situated on this mountain range and surrounded by ridges is an ideal depositional environment to reconstruct the paleo summer monsoonal record. A 204 cm long undisturbed sediment core recovered from this plateau has a 29.2 ka summer monsoon record. The LOI, total C, N, d13C, d15N, elemental ratios and compositional variability derived from diffused color reflectance, were measured at 1-3 cm resolution. These proxies show the changes in productivity and weathering/leaching, which are primarily based on precipitation. Age models were constructed using AMS ¹⁴C dating of total organic carbon in sediments.

Less productive, slow weathering/leaching dry-cold events and more productive rapid weathering/leaching wet-warm events are well correlated among multiple proxy records used. They well indicate the Henrich events I and II (H1 and H2) cold periods occurred around 25 and 16 ka. These cold events are followed by BØlling/AllerØd (BO) warm period occurred from 15-13 Ka. Yonger Dryas (YD) cold event can be clearly distinguished on this sediment record at around 12.5 ka. After that wet-warm conditions gradually increased till around 5 ka. Subsequently, a dry period occurred between 4-1 ka and wet conditions increased during the last 1ka period.

This climate record clearly indicates the link between northern hemisphere climate and low latitude Indian Ocean which could be controlled by thermohaline circulation as well as atmospheric circulation.