LASER AR-40 AR-39 DATING OF SINGLE DETRITAL MUSCOVITE GRAINS FROM EARLY FORELAND-BASIN SEDIMENTARY DEPOSITS IN INDIA - IMPLICATIONS FOR EARLY HIMALAYAN EVOLUTION/

In India, the Dagshai and overlying Kasauli Formations represent the o ldest exposed continental foredeep sediments eroded from the Himalayan orogen. Ar-40/Ar-39 dating of individual detrital white micas from th ese sedimentary units has provided maximum depositional ages of <28 Ma for the Dagshai Formation at one locality and <25 Ma at a second loca lity, whereas deposition of the Kasauli Formation occurred after 28 Ma at two localities and after 22 Ma at a third locality. This timing su ggests that, in India, the start of substantial exhumation and erosion from the rising Himalayan orogen was delayed until 28 Ma.