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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
