Stratigraphic and micropaleontological constraints on the middle Eocene age of the mammal-bearing Kuldana Formation of Pakistan

ABSTRACT

The Kuldana Formation of Pakistan is best known for its fossil mammals, including primitive cetaceans such as Pakicetus and its close relatives. Kuldana mammals have been regarded in different studies as early Lutetian in age (early middle Eocene), late Ypresian (late early Eocene), or, recently, to span much of Ypresian through early Lutetian time (early part of the early Eocene through the early middle Eocene). The Kuldana Formation is a relatively thin, 20-120 m thick low-sea-stand tongue of continental red beds lying within a much thicker sequence of foraminifera-rich marine formations. Planktonic and shallow benthic forams constrain the age of the Kuldana Formation to the late early Eocene or the early middle Eocene, and current interpretation of global sea level stratigraphy favors the latter. The short duration of the low-sea-stand interval when Kuldana mammals are found means that differences between samples recovered to date probably represent differences in local living environments, sites of deposition, and sampling, rather than any substantial difference in age. This reinforces an interpretation first proposed from the perspective of coeval Kalakot mammals recovered from the Subathu Formation in India.