Dense mineral data from the northwestern Himalayan foreland sedimentary rocks and recent river sediments: evaluation of the hinterland
The World's largest peripheral foreland basin, developed in front of the rising Himalaya, incorporates a sedimentary pile on the order of 10 4 m in thickness. Temporal variation in the heavy mineral record exists in the northwestern Himalayan Foreland succession due to a change in the composition of the hinterland. This study was conducted in order to correlate the heavy minerals occurring in sedimentary rocks with those of the present day small rivers/streams flowing exclusively either in the Higher Himalaya or in the Lesser Himalaya. The present study confirms some of the earlier views demonstrating temporal variation in the heavy minerals in the Cenozoic Himalayan Foreland sequences. In addition, their correlation with the heavy minerals of recent river-deposited sediments help in identifying exact sources which became positive areas due to tectonic rising of the Himalaya at different stages. The results suggest that the heavy mineral suites were mainly contributed from the low- to medium-grade metamorphic provenance at the initial stages and from the high-grade metamorphic provenance at the later stage of foreland sedimentation. This may be associated with the shifting of the channel pattern from axial to transverse as mountain chains grown in width over time. Also, Higher Himalayan Baspa river sediments contain staurolite and kyanite, in addition to tourmaline, epidote, garnet and other minor heavy minerals whereas Bhuzas stream sediments contain sillimanite in addition to staurolite, kyanite, tourmaline, epidote and garnet. Similarities in the heavy minerals exclusively derived from the Higher/Lesser Himalaya, and the Cenozoic heavy minerals of the Himalayan Foreland in the Jammu area suggest that staurolite is a contribution of the hinterland during the earlier stage and kyanite is a contribution of the Higher Himalaya during the later stage. Among the three mineral markers, the sillimanite-bearing suite was derived at a still later stage from the Lesser Himalaya and/or Higher Himalaya due to successive emplacement of the thrust sheets.