Integrated Ichnological and Sedimentological Analysis of the Cambrian Kunzam La (Parahio) Formation, Shian Section, Pin Valley, Spiti, Northwest Himalaya

Abstract

The Kunzam La (Parahio) Formation along the Shian section of the Pin Valley was previously interpreted as containing Ediacaran–Cambrian boundary trace fossils, but re-examination of the Shian section shows that the oldest part of the section belongs to the late part of Cambrian Series 2, Stage 4, which contradicts the previous interpretation. The trace fossil assemblage comprises ?Arborichnus isp., Archaeonassa isp., Diplichnites isp., Hormosiroidea isp., Monomorphichnus lineatus, Bergaueria aff. langi, Palaeophycus tubularis, Rusophycus isp., and Treptichnus-like fossils that occur stratigraphically below the Oryctocephalus indicus biozone (Series 3, Stage 5) along the section and belong to the late part of Series 2, Stage 4. Sedimentary structures recorded along the section include hummocky cross-stratification (HCS) with deeply bioturbated tops, trough- and low-angle cross stratification, ball and pillow structures and climbing-ripple cross stratification. Integrated ichnofabric and sedimentological data suggest a storm-dominated, lower to upper shoreface shallow-marine environment of deposition.