Early Cambrian Thalassinoides From the Mussoorie Syncline, Lesser Himalaya (India): Paleoecological, Paleoenvironmental and Biostratigraphic Significance

We report densely packed and multiple-layered Thalassinoides burrows network from the Calcareous Member (Deo-Ka-Tibba Formation, Tal Group) Mussoorie syncline documenting complex and high-density bioturbation in the Early Cambrian (Stage 4) shallow-marine environment. The Thalassinoides record from the Mussoorie syncline documents distinct colonization windows along the northern Indian margin that are comparable to those of South China, implying similar trace-maker densities and an Early Cambrian palaeobiogeographic extension of this ichnogenus in tidal-flat setting. This member is unconformably overlain by the siliciclastic-rich Dhaulagiri Formation, reflecting high-energy deposition with terrigenous influx. The stratigraphic correlation of the Calcareous Member supports a Cambrian (Stage 4) age, invalidating the earlier Stage 3 assignment. This discovery adds a distinctive ichnogenus to those already well known from Himalayan Cambrian rocks.