WHAT IS UNDERNEATH THE GANGA VALLEY? BIOSTRATIGRAPHIC AND DETRITAL ZIRCON AGE CONSTRAINTS ON THE PROTEROZOIC BASEMENT OF THE HIMALAYAN FORELAND BASIN

The pre-collision relationship between the Himalaya and cratonic India is of considerable importance for better understanding the tectonic history of the world’s largest mountain chain. The Cenozoic Himalayan foreland basin in the Ganga Valley, which sits between the Himalaya and cratonic India, is a key to assess this relationship. However, the sedimentary basement of the Ganga Valley, represented by the Ganga Supergroup, is entirely subsurface and only accessible through seismic imaging and drill cores. As such, geological information about the Ganga Supergroup is limited and its age is poorly constrained, hampering our ability to fully evaluate hypotheses about its relationship with sedimentary successions in the Lesser Himalaya to the north and cratonic India to the south. Using integrated biostratigraphic and detrital zircon data from drill core samples, we are able to constrain the Ganga Supergroup to be Proterozoic in age and to correlate it with the Vindhyan Supergroup on the Indian craton and Proterozoic successions in the Lesser Himalaya. These Proterozoic successions share a similar first-order stratigraphic architecture, with a late Paleoproterozoic–middle Mesoproterozoic package, a late Mesoproterozoic–early Neoproterozoic package, and an intervening unconformity. The new correlation suggests broad depositional continuity along the north Indian margin during the Proterozoic, and helps to reconstruct the geometry and tectonic history of Proterozoic basins in northern India.