Stratigraphic Evidence For An Early Collision Between Northwest India And Asia

THE collision of India with Asia(1) had a profound influence on late Cretaceous and Cenozoic oceanography(2), climate(3), faunal extinctions(4) and the motion of at least some of the Earth's lithospheric plates(5). As the collision ended a period of rapid Indo-Asian convergence, a precise knowledge of its timing (when the crust of the neo-Tethys ocean was completely subducted(7), at some point along the plate boundary) is important for understanding its wider consequences, But current estimates of the collision age range from 65 to 38 Myr before present(6,8-11), Here we report the results of extensive biostratigraphic analyses from Waziristan and Kurram in northwest Pakistan, which show that accretionary-prism and trench strata Were first thrust onto the northwest Indian passive margin after 66 Myr but before 55.5 Myr. After this time, volcanic-are fragments, the accretionary prism, trench material and imbricates of the north Indian slope were raised to shallow water depths and overlapped by upper Palaeocene shallow-water carbonates and shales(12-14), indicative of post-collision thrusting in this region. Finally, both the suture and the Indian craton were overlapped by continuous unconformable upper Lower Eocene shallow-marine strata, demonstrating that suturing was complete by 49 Myr.