Environment and Age of the Tal formation of Mussorie and Nilkanth Areas of Garhwal Himalaya

The Tal Formation in Mussorie area represents deposits of a shallow tidal sea. The basal black shale succession-with phosphorite, chert, and minor amounts of sandy layers and limestone bands is the deposit of a protected lagoon or embayment, followed by streaky siltstone facies, representing deposits of a protected tidal flat. Streaky siltstone shows characteristic features of mixed flat and mud flat of intertidal zone. The topmost thick quartzite succession is a deposit of a shoal complex of a tidal sea with rather high energy. Thus, from bottom towards top of the Tal succession, there is a gradual improvement in the circulation system, as well as increase in the energy of deposition. The fossiliferous shell limestone (Nilkanth Formation) is not a part of the Tal Formation, but represents deposits of a high-energy sand bar-shoal complex of a shallow tidal sea.

The Tal succession is devoid of any well defined body fossils and a Precambrian age is proposed. The fossil-bearing horizons occurring in association with the Tal Formation (hitherto considered to be part of Tal Formation) may belong to different age, namely, Carboniferous-Permian and Jurassic-Cretaceous; however, and these horizons do not appear to form part of the Tal succession.