Revised Tal Group lithostratigraphy and record of biostratigraphically significant <i>Shaanxilithes ningqiangensis</i> from Mussoorie syncline, Lesser Himalaya

A succession of bedded earthy argillaceous dolomite (~17 m) overlain by earthy siltstone (~12 m) is recognised in the lower part of the Deo-Ka-Tibba Formation (Tal Group) in the northeastern limb of the Mussoorie syncline, near Bhusti village. The recognition of these two diagnostic units necessitates a reclassification of the Tal Group in the Mussoorie syncline. This succession overlies the massive carbonate unit of the Krol-E (Krol Group) and underlies the Chert-Phosphorite Member of the Deo-Ka-Tibba Formation (Tal Group). Based on close lithological similarity with the sequence in the Nigalidhar syncline (Himachal Pradesh), these lithounits are designated Earthy Dolomite Member (EDM) and Earthy Siltstone Member (ESM), forming the lowermost part of the Deo-Ka-Tibba Formation. The Deo-Ka-Tibba Formation now includes six members: Earthy Dolomite, Earthy Siltstone, Chert-Phosphorite, Argillaceous, Arenaceous, and Calcareous. We also identified the Ediacaran body fossil Shaanxilithes ningqiangensis within the ESM, which indicates its deposition across the Ediacaran–Cambrian boundary interval, similar to that recorded in the Nigalidhar syncline (Himachal Pradesh). The present study establishes a precise litho-biostratigraphic correlation between the Mussoorie and Nigalidhar synclines of the Lesser Himalaya. The discovery of Shaanxilithes ningqiangensis recorded in the Lesser Himalaya is regionally and globally significant, and offers critical insight into the evolution of the dynamic stratigraphy during the transition from the latest Ediacaran to early Cambrian.