Evolution of Paleocene to Early Eocene larger benthic foraminifer assemblages of the Indus Basin, Pakistan

Abstract

Afzal, J., Williams, M., Leng, M.J., Aldridge, R.J. & Stephenson, M.H. 2011: Evolution of Paleocene to Early Eocene larger benthic foraminifer assemblages of the Indus Basin, Pakistan. Lethaia, Vol. 44, pp. 299–320. The Paleocene–Early Eocene carbonate successions of the Indus Basin in Pakistan formed on the northwestern continental shelf margin of the Indian Plate in the eastern Tethys Ocean. Based on larger benthic foraminifera (LBF), eight Tethyan foraminiferal biozones (SBZ1–SBZ8) spanning the Paleocene to Early Eocene interval are identified. The base of the Eocene is identified by the first appearance of Alveolina sp. Other stratigraphically important LBFs that are characteristic of the earliest Eocene are Ranikothalia nuttalli, Discocyclina dispansa and Assilina dandotica. Stable isotope analysis through the Paleocene–Eocene (P–E) boundary interval identifies more positive δ13C values for the Late Paleocene (+3.4‰ to +3.0‰) and lower values (+2.7‰ to +1.6‰) for the earliest Eocene. However, there is insufficient sampling resolution to identify the maximum negative δ13C excursion of the Paleocene–Eocene Thermal Maximum. During Late Paleocene times LBF assemblages in the Indus Basin were taxonomically close to those of west Tethys, facilitating biostratigraphic correlation. However, this faunal continuity is lost at the P–E boundary and the earliest Eocene succession lacks typical west Tethys Nummulites, while Alveolina are rare; LBFs such as Miscellanea and Ranikothalia continue to dominate in the Indus Basin. The absence of Nummulites from the earliest Eocene of Pakistan and rarity of Alveolina, elsewhere used as the prime marker for the base of the Eocene, may imply biogeographical barriers between east and west Tethys, perhaps caused by the initial stages of India‐Asia collision. Later, at the level of the Eocene SBZ8 Biozone, faunal links were re‐established and many foraminifera with west Tethys affinities appeared in east Tethys, suggesting the barriers to migration ceased. □Biostratigraphy, Eocene, India‐Asia collision, larger benthic foraminifera, palaeoecology, Paleocene.

Early Eocene orthophragminids and alveolinids from the Jafnayn Formation, N Oman: significance ofNemkovella stockariLess & Özcan, 2007 in Tethys

“…Calcareous nannoplankton zones (NP) are based on Martini (1971), and their correlation to the time scale is from Berggren et al (1995). (Afzal, Williams, Leng, Aldridge, & Stephenson, 2010;Ben Ismail-Lattrache et al, 2013;Özcan et al, 2014;Özcan, Hanif, Ali, & Yücel, 2015;Zhang, Willems, & Ding, 2013).…”

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

“…The few previous records of this species from Pakistan cannot safely be used for its geographic distribution during early Eocene because the species designations cannot be justified in vertical sections (e.g. D. dispansa in Afzal et al, 2010). O. schopeni, common to eastern and western Tethyan domains during early Eocene (Ferrández-Cañadell, 2002;Samanta, 1967), is the only orbitoclypeid known in eastern Tethys (Figure 15).…”

“…Consequently, D. ranikotensis has recurrently been reported from various stratigraphic levels ranging in age from late Paleocene to early middle Eocene in Pakistan, Iran, Italy and Slovakia. It was reported from late Paleocene (Afzal, Khan, Khan, Alam, & Jalal, 2005;Ahmad, 2010;Ahmad et al, 2014;Baruah & Das, 2007;Imraz, 2013;Latif, 1976;Sameeni, İmtiaz, Saleem, Haneef, & Naz, 2014;Sameeni, Nazir, Abdul-Karim, & Naz, 2009;Sigal et al, 1971;Yaseen, Rajpar, Munir, Roohi, & Rehman, 2011), late Paleocene to early Eocene (Afzal, 2010;Afzal et al, 2010;Butt, 1991;Hanif et al, 2013;Nagappa, 1959;Sameeni et al, 2014;Shafique, 2001;Weiss, 1993), early Eocene (Babazadeh, 2008(Babazadeh, , 2011Schweighauzer, 1953), from late Ypresian-early Lutetian (Mirza, Sameeni, Munir, & Yasin, 2005) and Middle Eocene (Köhler, 1967) (Figure 4). …”

“…The LBF in the early Palaeogene shallow-marine sediments of Himalayan belt play an important role in understanding the distribution of foraminiferal communities along the northern margin of Indian Plate, and their distribution and interaction in Tethys (Adams, 1983;Afzal et al, 2010;Haynes et al, 2010;Hottinger, 2009Hottinger, , 2014Zhang et al, 2013). It is generally agreed that LBF assemblages from Indo-Pakistan (eastern Tethys) and peri-Mediterranean regions (western Tethys) differ partly from each other across the P/E boundary, resulting in the formation of bioprovinces across the Tethys Hottinger, 1998Hottinger, , 2009Hottinger, , 2014.…”

“…The LBF assemblages of the 'Lockhartia Sea', an eastern Tethyan biogeographic province, have been extensively studied from Paleocene and early Eocene sediments in Pakistan, India, Tibet and Oman, although orthophragminids still remain poorly known (Afzal, Williams, Leng, Aldridge, & Stephenson, 2010;Davies, 1927;Davies & Pinfold, 1937;Eames, 1951aEames, , 1951bHaynes, Racey, & Whittaker, 2010;He, Zhang, Hu, & Sheng, 1976;Hottinger, 2009Hottinger, , 2014Racey, 1995;Zhang, Willems, & Ding, 2013). The previous records of orthophragminids in 'upper Paleocene' -lower Eocene sediments in Pakistan mostly refer only to Discocyclina ranikotensis Davies, 1927, a poorly known species considered to be endemic to Tethyan Himalayas in Indo-Pakistan region, suggesting a less diverse character of eastern Tethys orthophragminids compared to those of western Tethys in this time span.…”