THE DIVERSITY PATTERN OF LARGER BENTHIC FORAMINIFERA DURING THE MIDDLE EOCENE CLIMATIC OPTIMUM IN THE NORTHERN INDIAN PLATE MARGIN (PAKISTAN, EASTERN TETHYS)

Larger Benthic Foraminifera (LBF) were diverse and abundant organisms in warm, shallow water and oligotrophic Paleogene marine sediments in the northern Pakistan (eastern Tethys) though have been poorly considered for constraining paleoclimatic events. The present study aims to identify LBF turnover across the Middle Eocene ClimaticOptimum (MECO), a global warming event that representsan abrupt reversal in long-term cooling through the Eocene. The MECO is here identified in the shallow marine Kohat Formation, deposited in Sub Himalayas (NW Pakistan) that is the youngest eastern Tethyanmarine deposit. This formation is dominated by LBF including Nummulites, Alveolina, Assilina with addition of other fossils such as miliolids, orbitolites, Lockhartia, rotaliinids, and ostracods. The KohatFm is Middle Lutetian to LateBartonian in age. Microfacies analyses have been carried for determining the distribution of LBF in the Middle Eocene marine sediments of the Kohat Formation. Based on lithological, textural, sedimentary characteristics and association of LBF, six major microfacies have been recognized that are Assilina-NummulitesPeloidalwackestone-packstone, Orbitoliteswackestone-mudstone, Nummulites-Lockhartiawackestone, Assilina-Alveolinapackstone, Nummulites-miliolidwackestone-packstone and ostracodswackestone. These microfacies represent lagoon (inner carbonate ramp facies belt) to open marine (middle carbonate ramp facies belt). Our study documents variations in the LBF assemblages during the Bartonian. Alveolina sp. and Discocyclina sp. are abundant with large test size but got extinct during the Bartonian with first occurrences of Borelis species and reticulate Nummulites, which may have potential links to the globally recognized warming MECO event. The Paleogene period witnessed theIndia-Eurasia collision that has influenced the paleoclimatic conditions of Earth, thus evaluation of paleoclimatic parameters able us to constrain on the timing of India-Eurasia collision in this study.