Nar-Tsum Spilites Fm

A major regional unconformity; underlain by the Braga Fm (glacial diamictites) of upper Thini Chu Gr.

Followed by quartzose sandstones correlatable with member A of the Puchenpra Fm

"These spilitized tholeiitic basalts characterize the Nar-Burhi Gandaki region of northern Nepal, reaching a total thickness of 85 m in the Gya La area (Le Fort, 1975) and of about 300 m in the Samdo area (Fuchs and Paudel, 1998). The lava flows extend as far as western S. Tibet, where they are reduced to a few tens of metres and rapidly pinch out eastwards. The lavas (Bhote Kosi Basalts of Garzanti et al., 1999) here abruptly overlie diamictites of the Jilong Gr and are followed by quartzose sandstones correlatable with member A of the Puchenpra Fm (Qubu Fm of Sun, 1993). The overlying Qubuerga Fm contains Roadian brachiopods in its lower part (Garzanti and Angiolini, 1999)."

"Further to the east of Dolpo, from the Nar-Tsum region of Nepal to the Bhote Kosi Valley of S. Tibet, spilitic lava flows are found at the base of the drift sequence (Bordet et al., 1975, p. 97; Le Fort, 1975). Eruption of similar Lower Permian tholeiitic basalts, from the Panjal Traps of the N.W. Himalaya to the Abor Volcanics of Arunachal Pradesh, is interpreted as directly related to onset of seafloor spreading in the Neotethys Ocean (Garzanti et al., 1999)."