In the southwestern Sulaiman geological province (Balochistan, Pakistan), terrestrial detrital
facies from the Bugti Hills region have yielded the richest Tertiary vertebrate faunas to be found in
Asia thus far. New fossils from five successive and distinct ‘bone beds’ bridge the supposed Oligocene
sedimentary hiatus within the Sulaiman geological province; the lowermost continental levels of the
previously described Miocene Chitarwata Formation, known as the Bugti Member, are Oligocene in
age in the Bugti area. Neither a mixture of heterochronic faunal elements nor endemism of any fauna
is evident in this area. Additional microfaunal material from the Bugti Member constrains an
Oligocene age for the lower Chitarwata Formation in Zinda Pir (northeast of the Bugti Hills). This
Oligocene transition between the marine Kirthar (Eocene) and continental Siwalik (Miocene) deposits
consists of a regressive fluvio-deltaic system occupying a vast floodplain. It represents an early-stage
molasse in the palaeo-Indus Basin which drained western orogenic highlands resulting from the collision
between the Indian and Eurasian plates.