SEDIMENTOLOGICAL STUDY OF PROTEROZOIC SAKNIDHAR FORMATION, LESSER GARHWAL HIMALAYA, UTTARAKHAND, INDIA

Abstract

Proterozoic Saknidhar Formation is commonly considered as a transitional facies between the argillaceous Chandpur Formation and arenaceous Nagthat Formation. Stratigraphic position of Saknidhar Formation in the stratigraphic succession of Garhwal Group is very ill represented. It has its significance as a transitional facies, yet it is not properly studied and represented. It is very important to understand the depositional history of Saknidhar Formation in order to properly understand the evolutionary history of Garhwal Group of Alaknanda Valley. Saknidhar Formation has a fault contact with the Blaini Formation in the south west. It is characterised by pink to cream coloured sandstone with “Zebra Banding” and grey to brownish grey coloured mudstone. The bottom part of the succession shows evidence of deposition in a fluvial setting. Lithology of the middle part of the succession indicates a fluvial-marine transitional condition of deposition. The topmost part was deposited in a tidal flat setting. Depositional model indicates an increasing tidal influence in the sedimentation pattern, which is evident from the vertical distribution of facies in the sedimentary succession. Increasing tidal influence can be interpreted as a result of either rising sea level or basinal subsidence resulting from tectonic activities within the basin.