Evolution of the Western Himalayan Foreland Basin

Group was deposited in the meandering and braided rivers.The river system was axial in the beginning followed by transverse during the upper Siwalik sedimentation.Petrographic study of the sanstones of the lower Murree and the upper Murree formations show the occurrence of quartz, feldspar and rock fragments of phyllite, quartzite and siltstone and shale.In Q-F-L and Qm-F-Lt diagrams, the sandstones occupy the recycled orogen field.Heavy minerals study of these sandstones shows the presence of staurolite, tourmaline and garnet.The lower Siwalik succession contains heavy minerals such as tourmaline, staurolite, garnet, epidote, zircon and spinel, besides opaques.The middle Siwalik succession contains staurolite, kyanite, garnet epidote and zircon among nonopaque heavy minerals.The upper Siwalik succession contains staurolite, kyanite, sillimanite, garnet, epidote and zircon among the non-opaque heavy minerals.The three subgroups of the Siwalik Group show the similar zonation in terms of the occurrence of staurolite, kyanite and sillimanite in other areas too of the Himalaya similar to the Jammu area and can be correlated based on them.The Subathu shales were mainly constituted of the sediments derived from metamorphic rocks of the Ladakh and Kohistan arc and the Indus-Suture zone and the limestones suggest sediment starvation.The sandstones and mudstones of the Murree Group were derived from the metamorphic rocks occurring in the Higher Himalaya and sedimentary sequences of the Tethyan Himalaya.The occurrence of the staurolite further suggests that the provenance had been a low grade metamorphic rock during the sedimentaion of the Murree sequences.The lower and middle Siwalik sandstones were mainly constituted of the sediments derived from the Higher Himalaya, while the upper Siwalik sandstones were contributed from the sediments derived from the lesser Himalaya.Furthermore, the chemical compositions of the Subathu shales and Murree sandstones representing foreland sediments suggest that they have either intermediate composition between the active and passive margins or same as the passive margin.