Eleven dinoflagellates, acritarchs, and pollen biozones have been identified in Upper Eocene to Pliocene sediments combined from MuS, Tekman, Tercan-ASkale, Pasinler-Horasan basins and the Bayburt-Kars Plateau in this study. FAD&amp / #8217 / s of Compositae (tubuliflorae type), Slowakipollenites hipoph&auml / eoides, Mediocolpopollis compactus, Monoporopollenites gramineoides and Umbelliferae at the base of Rupelian, FAD of Wetzeliella gochtii in the middle Rupelian, LAD of Ascostomocystis potane in the late Rupelian, LAD of Wetzeliella gochtii in the latest Rupelian, LAD of Deflandrea spp. in the latest Chattian, peak occurrences of Chriptoredium spp. in the early and late Aquitanian, FAD of Hystrichosphaeropsis obscura, followed by FAD of Membranilarnacea ?picena in the late Aquitanian should have particular emphasis for palynostratigraphic divisions in regional correlations and indicate that a continuous deposition took place in Eastern Anatolia from Late Eocene to the end of the Early Miocene. A relatively deeper marine deposition prevailed during the Late Eocene, which was followed by a shallowing-upward deposition during the Oligocene in MuS, Tekman, Tercan-ASkale, and Pasinler-Horasan basins. These basins were also characterized by an Early Miocene regional transgression, and terrestrial (lacustrine and fluvial) deposition during the Late Miocene-Pliocene whereas terrestrial conditions have been predominating since Late Eocene in the Bayburt-Kars Plateau. Paleoclimatological reconstructions of Eastern Anatolian Oligocene-Miocene sediments suggest temperate to subtropical climates in which mean annual temperatures vary between 15,6 to 21,3 &deg / C, mean temperatures of the coldest and the warmest month are 5.0 to 13.3 &deg / C and 24.7 to 28.1 &deg / C, respectively, and mean annual precipitation is 1122.0 to 1522.0 mm.

Abstract The Surma basin is a part of the Bengal Basin situated in northeastern Bangladesh. The presence of eight gas fields and one oil field makes this an area that is interesting both economically and geologically. In spite of detailed geological and geophysical investigations, information available on palynostratigraphy and geochemistry for the area is scanty. The aim of the present work was to investigate the palynological assemblages, mineralogy and geochemistry of the Surma Group (SG) sequences in Surma Basin, Bangladesh. Core samples (n = 188) were gathered from the wells following: Patharia well-5, Rashidpur well-1, Atgram well-IX, Habiganj well-1, Kailastila well-1 and Fenchuganj well-2. They were provided by BAPEX (Bangladesh Petroleum Exploration Company). X-ray Fluorescence (XRF), Atomic Absorption Spectrometry (AAS), Loss of Ignition (LOI), X-ray diffraction (XRD), Transmission Electron Microscopy (TEM) and Scanning Electron Microscopy (SEM) were used for geochemical and mineralogical study of shale samples. In the palynological study, the distributions of pollens and spores were determined. For data analysis, SPSS computer programme was used. Palynological assemblages of the Surma Group of sedimentary sequence of Bangladesh include taxa range in age from the lower Miocene to the Upper Miocene which can be potentially used in dating and correlation. The Lower Miocene interval is correlated with the Simsang Palynological Zone IV of Meghalaya, India and the Bengal Palynological Zone (BPZ) V. The Upper Miocene is correlated with the Simsang Palynological Zone IV of Meghalaya, India and the BPZ Zone V of Bengal. They were deposited in two types of paleoenvironments ranging from the brackish type to shallow marine to brackish. The sequence contains reworked palynomorphs of BPZ IV and III namely Meyeripollies naharkotensis, Polypodiesporites Oligocenecus, Palmepollenities Eocencus and ornamented Tricolpate pollen of the Eocene-Oligocene age which are mainly encountered in the lower Miocene sediments indicative of increased tectonic activity in the area. Geochemical ratios (SiO2/ Al2O3, Cu/Zn, Maturity = K2O+ Al2O3/Na2O+MgO, Rb/K2O, K2O/Na2O, Cr/Rb, Zr/Rb, V/Rb, Th/U etc.) were useful for determining grain size, maturity, tectonics and environment of deposition. High Ba enrichment was detected in the Patharia well-5 and showed high surface water productivity and diagenetic mobilisation. Tectonic descrimination was achieved using SiO2 and K2O/Na2O ratio. XRD analysis revealed the minerals kaolinite, illite, chlorite, illite/smectite (I/S) and kaolinite/smectite (K/S) mixed layers. Kaolinite/Smectite here reported for the first time in Bangladesh. Clay mineral analyses provided evidence for diagenesis. Smectite diagenesis and dehydration have contributed to the generation of overpressure in the Bhuban Formation in the Patharia well -5. Geochemical ratios of the present study from the Surma Basin is undoubtedly a powerful technique and can be applied to any sedimentary basin analysis to infer the palaeoenvironment, palaeoclimate and palaeotectonics.