A New Approach to the Lithostratigraphy of the Cenozoic Sequence of Kerala

A lithostratigraphic classification of the Cenozoic sedimentary sequence of the coastal plains of Kerala has been developed through an analysis of the exposed and subcrop litho-facies and their interrelationship based on sedimentologic parameters. The entire Cenozoic sequence is designated as the Malabar Supergroup comprising the Vembanad Formation (Quaternary-Holocene) and the Warkalli Group (Tertiary) separated by an unconformity marked by laterite. The Warkalli Group comprises the Ambalapuzha, the Quilon and the Mayyanad Formations from top to bottom. The Ambalapuzha and the Mayyanad Formations are basin margin fluvial and deltaic facies comprising sandstones, clays and lignites, and having a wedge of calcareous platform facies of the Quilon Formation. With the thinning out of the Quilon Formation (calcareous facies) in the eastern margin of the basin, the distinction between the constituent formations of the Warkalli Group disappears. Thus the purely terrigenous sediments in the eastern and southern margins of the basin form a single non-classifiable unit, the Warkalli Formation.