PETROGRAPHY AND LITHOFACIES CHANGE OF TIYON FORMATION (MIDDLE EOCENE) LOWER INDUS BASIN, SINDH

Abstract

The study dealing with petrography, lithofacies and sedimentology of Tiyon formation help in correlation regionally and globally. During the Early-Middle Eocene rapid transgression and locally regression in Southern Lower Indus Basin deposited limestone interbedded shale in Tiyon formation in between Laki and Kirthar Formation. The main lithofacies distributed in Tiyon formation is limestone, nodular and marly limestone, highly fossilifereous with interbedded silty calcareous shale. The microfacies are mudstone, wackstone, packstone and grainstone with dominant Alveolinids, Assilina and Nummulities. The fauna are well preserved in similar lithofacies with minor change in France, Alpine, Himalayan and Indo-Pacific region. The Litho-biofacies of Tiyon formation indicates the marine transgression during Lutetian, west to east from Paris Basin through Libya, Egypt, Oman, Iraq, Iran, Turkey, Saudi Arabia, Afghanistan, Baluchistan, Sindh, Salt Range, Kutch, Rajasthan and Assam to Indonesia. The basal and middle part of the Tiyon formation yields Paracypris maridonalis, Paracypris sapperi, Schizoptocythere sp., Stigmatocythere oblique ostracods which are correlated to Saudi Arabia, Salt Range, Sor Range of Baluchistan and Kutch (India) area but in the middle to upper part Bairoloppilata and Krithe rutoti are common in Paris, Belgium and England. The presence of abundant gastropod species Velates perversus in European countries also confirms the Lutetian transgression from west to east Tethys. The upper part of Tiyon formation consists of Alveolina elongata, Nummulities obtusus, N. pinfoldi and N. perforatus indicates the Late Lutetian - Early Bartonian. The Tiyon formation is correlated with Pir Koh Limestone, lower part of Drazinda shale of Zinda Pir, Drug area (D.G. Khan) Punjab, basal shale unit of the Kirthar Formation and upper most beds of Ghazij Shale exposed in the Sore-Range, Chorgali Formation, Kuldana Formation, Basal part of Kohat formation and Sakesar Formation The Tiyon formation is the unit of Chat member of Laki Formation. This distinct lithological unit with different stratigraphic position should be formalized as a separate formation. The Tiyon formation is deposited in inner to outer platform with normal salinity, clear and warm water conditions most appropriate for the flourishing of shallow marine faunal assemblages. The age of Tiyon formation represent the Late Ypresian-Early Bartonian stage of Middle Eocene.