Early Eocene orthophragminids (Foraminifera) from the type-locality of Discocyclina ranikotensis Davies, 1927, Thal, NW Himalayas, Pakistan: Insights into the orthophragminid palaeobiogeography

Abstract

The study of isolated orthophragminid tests at the type-locality of Discocyclina ranikotensis Davies from the Patala Formation in Thal area (Upper Indus Basin, NW Pakistan) revealed new associations of genera Discocyclina Gümbel, and Orbitoclypeus Silvestri, not yet reported from eastern Tethys. We demonstrate that D. ranikotensis Davies, the species identity of which has been a subject of controversy in earlier works, is a valid species endemic at least to the Indo-Pakistan region. D. ranikotensis is associated with Discocyclina archiaci (Schlumberger), and very sparse Orbitoclypeus schopeni (Checchia-Rispoli), both species being key taxa for orthophragminid zonation in peri-Mediterranean Tethys. We have also identified a few discocyclinid specimens suggesting possible connection to western Tethys species D. fortisi, and a few specimens showing affinity to D. dispansa. The assemblages of orthophragminids suggest orthophragminid zone (OZ) 3 according to western Tethyan zonation scheme. The occurrence of D. archiaci extends the geographical distribution of this taxon to eastern Tethys, which hitherto was only known from peri-Mediterranean region. The typical western Tethyan asterocyclinids, nemkovellids and ribbed orbitoclypeids, first appearing at or around Paleocene/Eocene boundary (OZ 1B/2, SBZ4/5), have not been identified.