Triassic Microfauna of the Lilang Group with Special Reference to Scythian-Anisian Conodonts, Spiti Valley, Himachal Himalaya

Abstract

The Triassic microfauna from the type section of the Lilang Group recorded here includes conodonts (58 taxa), foraminifera (17 taxa), ostracoda (5 taxa) and radiolaria (one taxon).

Except for one form in the Carnian Sanglung Formatiqn, the conodonts are exclusive to the Scythian-Anisian Mikin Formation. The foraminifers come mainly from the Mikin, Norian Hangrang and Rhaetian-Dogger Kioto Formations. In the former two, they are rare, while in the last one common. The ostracodes chiefly occur in the Mikin Formation. The radiolarians are common in the Carnian Chomule Formation and sporadic in the Mikin Formation.

Based on microfacies analysis, the Mikin, Chomule and Sanglung Formations are interpreted to represent clear basin margin, Hangrang back-reef to fores]ope and Kioto restricted platform to edge-sand and lagoon environments. The varying abundance of the microfauna in different formations is possibly environmentally controlled. The conodonts, and radiolaria preferred basin margin, and foraminifers restricted platform to edge-sand and lagoon environments.