Late Cretaceous and Early Tertiary Benthic Foraminiferal Biostratigraphy in Khuzdar District, Balochistan, Pakistan, with Special Reference to the Influence of Tethyan Sea Closure

The paleontological study of benthic foraminifera in relation to the Indian-Asian boundary in Khuzdar District, Balochistan, Pakistan, have been carried in three sections of the Cretaceous-Paleogene: named as 1) PAK-section, 2) MG-section and 3) HR-section (Abbr.) of Hinar. Strata of the three sections contain typical Cretaceous-lower Tertiary benthic foraminifers such as Bolivinoides draco, Coryphostoma incrassata, C. midwayensis, Gavelinella monterelensis, Globorotalites micheliniana, Stensioina beccariiformis, S. excolata, Neoflabellina rugosa, Nuttallides truempyi and Vulvulina spinosa. Fifteen benthic foraminiferal assemblages have been recognized from the PAK-section (seven assemblages) and MG-section (eight assemblages). The Cretaceous-Paleogene strata are defined into three lithostratigraphic units consisting of the Mughal Kot Formation, the Pab Sandstone and the Jamburo Group in the ascending order. The age of the redefined Jamburo Group ranges from the Maastrichtian to the Middle Oligocene. The Cretaceous bearing strata of the Jamburo Group below the Pab Sandstone are correlated to the Mughal Kot Formation. The Cretaceous-Tertiary boundary is determined above the Pab Sandstone and the base of the Jamburo Group in the PAK-section and below coarse grained brecciated limestone in the MG-section. Whereas in the Hinar section, it is located between limestone and shale of the Jamburo Group, by the disappearance of such planktonic foraminifers as Globotruncana stuartiformis, G. falsostuarti, Gl. spp., Pseudoguembelina elegans and Recemiguembelina fructicosa and the appearance of the Danian Globorotalia pseudobulloides. The Cretaceous specimens occurring in the lower parts of the MG-section and PAK-section indicate Maastrichtian that is the age of the above mentioned Mughal Kot Formation and Pab Sandstone. Overall the redefined Jamburo Group consists of various kinds of shale, limestone, shelly limestone and marlstone. The late Cretaceous Mughal Kot Formation reveals more distinct alternation of limestone and shale, with two to three meter thick sandstone separated as a different unit equivalent to the Maastrichtian Pab Sandstone. Benthic foraminifers change their tests from calcareous to agglutinated across the Cretaceous-Tertiary boundary. The change is most obvious in the PAK-section. However, the frequency of agglutinated taxa shows fluctuation in the Paleogene of the HR-section, and in the MG-section the agglutinated ratio does not largely change at the K/T boundary and gradually decreases afterwards. This decreasing tendency may be associated with restriction of the bottom water circulation of deeper water which may be caused by closure of the Tethyan Sea, and supports the hypothesis of collision of Eurasian and Indian Plates near the end of the Cretaceous and the Early Paleocene to Eocene

First report of a bothremydid turtle, Sindhochelys ragei n. gen., n. sp., from the early Paleocene of Pakistan, systematic and palaeobiogeographic implications

International audienceWe report the discovery of remains of a large chelonian from the base of the early Paleocene Khadro Formation exposed in the Ranikot Fort area (Ranikot Group, Sindh Province, Southern Pakistan). This formation already yielded the snake Gigantophis Andrews, 1901, studied by our friend Jean-Claude Rage. The chelonian specimens consist of a large carapace and a shell fragment of Bothremydidae, a family of Gondwanan origin. A new genus and species, Sindhochelys ragei n. gen., n. sp. is identified from the first specimen and named in honor of Jean-Claude Rage. It is the first report of a Bothremydidae in Southern Pakistan. Its affinities with Cretaceous and Paleocene representatives of the family are discussed. The association of characters such as the shape of the shell, anterior plastral scute pattern and strongly marked decoration characterize the taxon and, despite some similarities, allows excluding close phylogenetic affinities with Taphrosphyini and Carteremys group; other well-documented bothremydids are also excluded. The shell fragment, also strongly decorated, is left undetermined. The discovery of two new littoral bothremydid specimens in the early Paleocene of Pakistan fills a geographic and stratigraphic gap in our knowledge of the family, which is known since the continental early Cretaceous of Africa, diversifying in the world up to the Miocene deposits of the Neotethys. A particular diversification during the Maastrichtian-Paleocene is recognized along the neotethyan coasts, and occasional dispersals across this ocean were possible. Sindhochelys ragei n. gen., n. sp. may have colonized the Indian subcontinent by this time, or may represent an older diversification before the Gondwana breakup