Grain Size and Magnetic Susceptibility Assessments as a Tool for Understanding the Sedimentary Environment of Pykara Lake, Tamil Nadu, India

Abstract

The sediment analysis and its textural characteristics were carried out for 10 surface samples collected from the various parts of the lake and one core sample permit to infer the changes in the depositional environment during the period of infilling at the sites. Extreme variation in the velocity of the depositional agent and lack of certain grain size in the source material leads to the polymodality in the nature of the frequency curve. The core sediment expressed coarse silt to very fine silt size, moderately to very poorly sorted, and near-symmetrical to very fine skewed type. The surface sediments show fine sand to coarse silt size, poorly sorted to very poorly sorted, and very fine skewed in nature. Both the core as well as surface samples exhibit platykurtic to very leptokurtic characteristics. The CM diagram shows that most of the core and surface sediment samples possess suspension of minor importance while other sediments are deposited by rolling and suspension, suspension and rolling, graded suspension, and uniform suspension respectively and some core sediments also depicted pelagic suspension. From the magnetic susceptibility studies, it has been observed that the samples from the study area are fine grain and exhibits ferromagnetic in nature. The magnetic susceptibility conveyed the lake experienced both god and lack of supply of sediments into the lake. The variation in the supply of sediments into the lake advocates sediment depositions are climatic dependent and also the lake experiences fluctuation in higher hydrodynamic energy.