A Plate Tectonic Model for the Geologic Evolution of Sri Lanka

Abstract

A new model is put forward to explain the geologic evolution of Sri Lanka. The Highland Group is a highly metamorphosed assemblage of a marine deposited volcanic, volcano-clastic and sedimentary rocks. The origin of the Highland Group dates back to 3000 Ma during a permobile phase in the evolution of the earths crust. Archaean tectonics suggest a downfolding of a thin crust forming the Highland Basin and subsequent filling with marine sediments and volcanics. The tectonic characteristics of the Archean suggest that its evolution possibly passed through a transitional phase (during which the crust thickened) to a plate tectonic phase. Plate tectonic processes analogous to those of the present were active from 2000 Ma. The material in the Highland Basin was metamorphosed and deformed repeatedly, in a collisional tectonic environment, to form the present configuration in the Precambrian of Sri Lanka.