Textural characteristics of the surface sediments of a tropical mangrove Sundarban ecosystem India

摘要

Surficial sediments of Sundarban Mangroves in West Bengal India have been studied for grain size spectrum and textural parameters namely phi mean, standard deviation, skewness and kurtosis. Grain size spectrum shows a marked variation in the upstream riverine stretch. Observed variation of energy conditions is controlled by the fluvial profile in the channel. Textural pattern is highly complex owing to the fluctuation in the physico-chemical conditions prevailing in the system. Textural analysis of very fine sand shows existence of comparatively low energy condition in the fluvial and mangrove creek zones. Linear Discriminant Function Analysis (LDF) of the samples indicates a shallow marine environment origin for all samples of the mangrove ecosystem; The riverine sediments also show a wide range of textural facies. They show a progressive enrichment of silty-sand in the downstream in the creeks. The CM diagram (C=one percentile in microns, M=Median in microns) of Sundarban suggests that sediment deposition takes place by (1) rolling (2) rolling and suspension and (3) graded suspension. The river and creeks sediments represent deposits are of uniform suspension.