Revised stratigraphy of the lower Cenozoic succession of the Greater Indus Basin in Pakistan

Abstract

Abstract. A refined stratigraphy for the lower Cenozoic succession of the Greater Indus Basin in Pakistan is presented. This region preserves an important East Tethyan marine succession through the Paleocene–Eocene, but its interpretation in terms of regional (tectonic) and global (climatic) effects has been inhibited by poor stratigraphy. Established dinoflagellate, nannofossil, planktonic foraminiferal and shallow benthonic foraminiferal biostratigraphical data for the Greater Indus Basin in Pakistan are collated, reinterpreted (where necessary) and correlated with the global standard chronostratigraphy and biostratigraphy of the early Palaeogene. Inter-regional stratigraphical correlations for the Upper Indus Basin and Lower Indus Basin are resolved. Age-diagnostic larger benthonic foraminifera from the Late Paleocene Lockhart Formation are illustrated. These collective biostratigraphical data provide a means of interpreting the lithostratigraphy and physical stratigraphical relationships of the Palaeogene succession in terms of the interplay between local tectonics (India–Asia collision) and global sea-level change. The timing of the Tethys closure, initial and final contact of the Indian–Asian plates, and dispersal of land mammals on the Indian Plate are discussed and correlated in the stratigraphical record of the basin.

Early Eocene orthophragminids (Foraminifera) from the type-locality ofDiscocyclina ranikotensisDavies, 1927, Thal, NW Himalayas, Pakistan: insights into the orthophragminid palaeobiogeography

“…According to Beck et al (1995), who provided the only planktonic foraminiferal data in the same area with our present work, Patala Formation covers planktonic foraminiferal P5 and P6 zones, implying a late Thanetian-early Eocene age, which is in accordance with the ages obtained from the Patala Formation in Salt Range and Kohat area (Afzal & Butt, 2000;Afzal & Daniels, 1991;Afzal et al, 2009). The calcareous nannofossils identified by Köthe et al (1988) from Patala Formation in Salt Range and Kohat area suggest Thanetian-early Eocene age based on the NP8-12 zones.…”

“…The calcareous nannofossils identified by Köthe et al (1988) from Patala Formation in Salt Range and Kohat area suggest Thanetian-early Eocene age based on the NP8-12 zones. With respect to LBF, previous studies identified SBZ 4-6 in Kohat area (Sameeni, Haneef, Rehman, & Lipps, 2009), SBZ4/5 in Surghar Range (Sameeni et al, 2014) and SBZ 4-9 in Kohat area and Salt Range (Afzal et al, 2009) that would indicate a Thanetian-early Eocene age for the Patala Formation. A late Thanetian-early Eocene age for the Patala Formation is also supported by the revised stratigraphic distribution of rotaliid species, such as Lockhartia haimei (SBZ 4-7), Lockhartia conditi (SBZ 4-8), Rotalia newboldi (SBZ 6-8) and miscellanids by Hottiger (2009Hottiger ( , 2014.…”

“…(1) Patala Formation ('upper Ranikot beds' of Davies, 1927): this unit comprises an inter-bedded sequence of marl, shale, siltstones and argillaceous limestones, and is interpreted to have been deposited in a variety of depositional environments ranging from shallow marine inner shelf to open marine (Afzal & Daniels, 1991;Afzal, Williams, & Aldridge, 2009;Davies & Pinfold, 1937;Hanif, Ali, & Afridi, 2013;Köthe, Khan, & Ashraf, 1988). Patala Formation, originally described from Salt Range in Pakistan (Davies & Pinfold, 1937), is widely distributed in fold-and thrust-belt in Upper Indus Basin in north Pakistan (Figure 1) and is richly fossiliferous with age-diagnostic LBF.…”

“…The late Ypresian age assignment for this unit given by Beck et al (1995) is based on the planktonic foraminifera that indicate P9 Zone. Considering the earlier ages given to this unit by LBF and mollusks, Afzal et al (2009) have assigned an age of early to middle Lutetian to Kohat Formation based on the LBF indicative of SBZ 14-16 zones.…”

“…This view, however, has been challenged by Khan et al (2003) arguing that this tectonic event was local, probably related with ophiolite obduction rather than India-Eurasia collision. Recently, Afzal et al (2009) have proposed that the closure of Tethys in Pakistan was initiated during the early Lutetian rather than early Eocene and was completed by the Priabonian by using foraminiferal and other fossil data from Indus Basin.…”