Stratigrafical Sediments and Paleo-Climate Changing Patterns in Kalu Ganga River Basin in Rathnapura of Sri Lanka

Abstract

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Geologically, Sri Lanka is an important place to study the erosion, transportation and deposition process of river flows. According to the geological time scale, these processes were evident during the quaternary period in Sri Lanka. Therefore, lots of sediments found within the low lands area around the country. The sediments were deposited around the country by the process ofriver erosion and transportation. The Kalu river basin is prominentfor sedimentation ofsuch river basins when compared with other river basins. It is in the Rathnapura district that high deposition has taken place. There is a stratigraphy in many types of sediment in the Kalu Ganga basin in terms ofthe depth ofsediments and number of layers. This research has attempted to study the way in which the above mentioned stratigraphy has taken place and which factors have caused the creation of such particular patterns. For this purpose, an investigation was carried out in 10 gem mines representing the lower catchment of the river through random sampling. GIS mapping, laboratory testing and statistical methods have been used for analyzing andpresenting data. Research results brought out very important findings in relation to the stratigraphy of sediments layers in the Kalu Ganga river basin. There was a spatial variation in the number and the depth of gem bearing sediment layers. Since the lake sediment layers are found in the lower catchment, it is suggested that there was paleo climate change during the Quaternaryperiod