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Devonian of India
In India, Devonian rocks are confined to the western part of the Himalayas and occur as scattered outcrops in Kashmir, Spiti and Byans. In Burma to the east and in Chitral area to the west, they show far better development.
In the type area of Spiti, the hard white quartzites called Muth Quartzite, 150 metres thick, have a gradual passage from fossiliferous Silurian rocks. Upwards, the quartzites pass into limestones containing Middle to Upper Devonian fossils, in turn overlain by fossiliferous Lower Carboniferous rocks. Stratigraphically, there is no break in deposition from the Silurian to the Middle Carboniferous.
In Kashmir, these quartzites are more than 600 metres thick and conformably overlie Upper Silurian rocks. Their upper contact, however, is with different formations, namely, the Syringothyris Limestone (Lower Carboniferous), and Agglomeratic Slates or Panjal Traps (Permo-Carboniferous). The quartzites themselves, long considered unfossiliferous, have recently yielded a Devonian fauna.
Rocks similar to the Muth Quartzites are exposed in the Kumaon and Niti areas also. Fossiliferous dark limestones of Givetian or Frasnian age are seen in Byans, near the Nepal border.
The uppermost part of the Jaunsars (Palaeozoic), called Nagthats in the Simla-Garhwal, Chakrata, and Dehra Dun-Mussoorie areas of the Himalayas, and the Tanawals of Kashmir, may be partly Devonian. These series are unfossiliferous and so their age cannot be definitely ascertained.
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