Preliminary palynological study of the Upper Ordovician Pin Formation in northern Indian Himalaya

Abstract

The Pin Formation of the northern Indian Himalaya may contain a record of the late Katian (Late Ordovician) warming event (the Boda Event). Palynological samples collected from two members of this formation are investigated in order to evaluate the biostratigraphical potential of the different microfossil groups. Acritarchs and chitinozoans are the most abundant microfossils, but fragments of scolecodonts and melanosclerites are also present. Several of the acritarchs from the Pin Formation are long-ranging through the lower Palaeozoic, but other taxa can be compared to Upper Ordovician (Katian) assemblages described from other parts of the world. The chitinozoan assemblages, consisting of 13 species (including those in open nomenclature) belonging to seven genera, are mainly recorded from two layers. The chitinozoan assemblage collected from the sample at 87.3 m in the uppermost part of the Farka Muth Member, and that collected at 184.89 m from the Takche Member, indicate a late Katian age. This age interpretation is in accordance with conodont data from the Takche Member, a positive carbon isotopic peak from the top of a shale unit in the Takche Member, and the initial part of the rapid negative shift of the Paroveja isotopic excursion related to the Boda Event of late Katian age. Further detailed studies with a higher number of samples are needed, that describe better preserved and more diversified palynomorph assemblages, which would help to more precisely refine the Upper Ordovician biostratigraphy in this area.