Status of the indian early cretaceous ammonoid record in light of recent observations in the spiti valley, Himachal Himalaya

Abstract

The present contribution enlightens the current understanding of the Early Cretaceous ammonoid record in India. Our recent work in the Spiti Valley suggests that the ammonoid bearing Early Cretaceous succession in the Spiti Himalaya, the Giumal Formation is ideal to carry out ammonoid based biostratigraphic studies. In view of the record of the ammonoid genera Odontodiscoceras and Berriasella from the basal sandstone bed and Colombiceras, Deshayesites, Cleoniceras and Australiceras from the upper most sandstone beds, the age of the Giumal Formation is précised to range from Berriasian to Early Aptian. The preliminary study of the freshly collected ammonoids suggests that the bases of the Berriasian, Valanginian and Aptian stages of the Early Cretaceous are marked, respectively, through the first appearances of the genera Odontodiscoceras, Olcostephanus and Cleoniceras. The succession is important for initiation of a new approach towards the recognition of Oceanic Anoxic Events, not attempted so far. © 2014 by the Wadia Institute of Himalayan Geology, Dehradun 248001, India.