Characterization of Ordovician-Silurian Acritarchs from the Kumaon Tethys Himalaya, Pithoragarh District, Uttarakhand, India

Abstract

Acritarchs, microphytoplankton of algal protists, from the Shiala and Yong Limestone formations of the Gunji village along Kali river (upstream) of Kumaon Tethyan Himalaya, Pithoragarh district, Uttrakhand, India have been examined for the first time. It aims to test the basin-wide existence and testing the reliability of already locally established biozones from the Garhwal Tethys Himalaya, Chamoli district, Uttrakhand. The study reveals moderate to poorly preserved, matured assemblages and diversified forms of acritarchs from both formations. The assemblage includes sphaeromorphs, acanthomorphs, netromorphs, polygonomorphs, diacromorphs, herkomorphs, etc. Two palynoassemblages have been recognized each from the Shiala and Yong Limestone formations. Palynoassemblage (I) from the Shiala Formation is confirmed by one productive sample which reveals a mix of Late Ordovician and Silurian forms. The acritarchs assemblage assigned to 16 genera with at least 13 species. The acritarchs from the Yong Limestone Formation are more plentiful and diverse confirming the Palynoassemblage (II) that contains biostratigraphically significant forms of typical Silurian (Ludlow) age. This Palynoassemblage is assigned to 23 genera with 16 species. The paper also describes the possible reasons for floral difference from the same formation and basin sampled at two different localities of the Tethys Himalaya, possibly due to palaeoclimatic constraints. However, detailed work on this aspect is required. The palynoassemblages from both the formations describe morphologically non-distinct, ubiquitous, wide palaeogeographic spread and uncertain stratigraphic taxa too along with biostratigraphic significant forms.