Asteriacites and other trace fossils from the Po Formation (Visean-Serpukhovian), Ganmachidam Hill, Spiti Valley (Himalaya) and its paleoenvironmental significance

Abstract

An assemblage of trace fossils comprising Asteriacites stelliformis, A. quinquefolius, Biformites insolitus, Helminthoidichnites isp., Lingulichnus isp., Lockeia siliquaria, Palaeophycus tubularis, Planolites isp., Protovirgularia isp. A, Protovirgularia isp. B, Protovirgularia isp. C, Psammichnites isp., Rusophycus isp., and Treptichnus isp. from the Po Formation (Visean-Serpukhovian) exposed along the base of Ganmachidam Hill near the village of Chichong, Spiti Valley in the Himalaya, is described. Storm beds (tempestites) are highly bioturbated. Sedimentary structures such as hummocky cross-stratification (HCS), low-angle planar and trough cross beds, and shallow, slightly asymmetrical gutter casts are observed. The overall trace fossil assemblage indicates the presence of upper shoreface to lower shoreface Cruziana ichnofacies of an open shelf.