Composition and Provenance of Clay Minerals in the Northern Part of Lake Tonle Sap, Cambodia

Abstract

Unique sedimentary processes under the control of drastic seasonal fluctuations in its water level and area are expected in Lake Tonle Sap, the largest lake in Southeast Asia. As a part in a series on pursuing the sedimentary processes and their temporal changes of the lake, sediments and soils were collected and examined from the northern part of the lake and its adjacent water systems and areas in order to reveal composition and provenance of clay minerals distributed in the northern part of the lake.
Illite, kaolin minerals, smectite and chlorite were commonly identified from the surface and suspended sediments of the lake. Judging from illite and chlorite are not detected in the sediment and soil samples from rivers and the Alluvial plains around the lake but the bottom sediments from the Tonle Sap River that connects the lake with the Mekong River yield a certain amount of them, it is stated that illite and chlorite recognized in the lake sediments were derived from the Mekong River. Since illite and chlorite are not detected in the lower part of the cored sediments from the northern part of the lake in spite of the upper part contains them, appearance of illite and chlorite in the upper part of the core indicates that a change of sediment transport in water systems around the lake took place at about 5, 000 years BP.