Close Grid Gravity Surveys at Varkala Beach, Kerala.

摘要

Varkala beach, along the south west coast of Kerala, the present study area, is narrow with silver sands and is flanked by ~ 30 m cliff immediately to the east. The cliff section runs parallel to the coast line over a kilometer and exposes the litho units ranging from Tertiary to recent. Varkala and adjacent area forms a part of Kerala Khondalite Belt (KKB) of the Southern Granulite Terrain (SGT). The Precambrian crystalline of the area is unconformably overlain by Tertiary sequence of Warkalli formation of Mio- Pliocene age. The Warkalli formation comprises unconsolidated sands, variegated clays, white plastic clays, carbonaceous clay and lenses of lignite. At Varkala beach the basement is dipping towards east resulting in thickening of sedimentary rocks away from the beach. Gravity data indicates a fault along the contact between the beach and cliff with thick sequence of sediments in the down thrown block. In the second phase of tectonic event, this sediment deposited on the down thrown block was uplifted gaving rise to the present topography as a cliff. The thick clay layer present over the basement is the major geological factor causing wave undercutting as well over hang collapse.