Depositional Environment of Neogene Foreland Deposits (Manchar Formation) from the Bara Nai Section of the Southern Indus Basin, Pakistan

Paleogeography of the Foreland Deposits

Abstract

Study of depositional environment of the Neogene deposits are important for their potential   to uncover the paleogeography of the foreland basins. The paleogeography on the other hand is the sum of interactions between the tectonism, climate and sedimentary processes in a basin. The depositional environment of the Neogene foreland deposits exposed in Bara Nai section of Southern Indus Basin is poorly understood. The present study is aimed to understand the broad depositional environment of these deposits through analysis of primary sedimentary features and textural characteristics of the sandstone. The primary sedimentary structures include cross bedding and strata containing planar-lamination. Other depositional features include oxidized beds, mammal bones and petrified wood. The studied sandstones are medium to fine grained. The sandstones are mostly moderately sorted with a few showing poor sorting. The skewness range of the studied sediments shows coarse-skewed to near symmetrical, while the average skewness curves are near asymmetrical in nature. The kurtosis of the studied samples shows platykurtic nature and some represent mesokurtic and leptokurtic feature. Field sedimentologic studies and granulometric analysis involving linear discriminate functions reveal that the Neogene Manchar formation in the Bara Nai section was deposited in a fluvio-deltaic environment during Neogene.