Optically Stimulated Luminescence (OSL) Dating of Sediments from Himalaya

Abstract

Optically Stimulated Luminescence (OSL) dating gives the age of most recent daylight exposure or heating of samples to >400°C or the formation events of authigenic minerals. These correspond to the age of sedimentation and burial, ages of thermal events like contact heating by lava flows and heating during faulting and sand dyke formation, and the formation of a mineral via chemical precipitation. With the first observation of OSL in 1985, this method now occupies centre stage in Quaternary Geochronology. The use of OSL method for sediments from Himalaya began over three decades ago. The method has since provided chronology for a variety of events, such as past glaciation events, formation ages of river terraces, paleo–lacustrine deposits, landslides, floods, seismic events with substantive new insights into timing and style of geological processes.

Theoretically, the dating range of method is present to a Million years, and this critically depends on two factors, viz. luminescence properties of mineral and their radiation environments. The general working range using quartz is 200ka, and using feldspars is up to Brunhes Matuyam Boundary. Extensions beyond this limit are currently being explored.