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Jurassic and Triassic coals and organic matter-rich shales of the Tabas Basin,Iran,were investigated with respect to their thermal maturation and petrographic composition.The Triassic coals of the Parvadeh coal field range in vitrinite reflectance between 1.17% and 1.37% and the Jurassic coals of the Mazino coal field between 2.08% and 2.29% VRr.Maceral analysis revealed a predominance of vitrinite in all samples,with slightly higher percentages of inertinite in the Jurassic samples.Rock-Eval analyses confirm the presence of type Ⅲ kerogen in the Triassic coals,while the Jurassic coals contain strongly carbonized residual kerogen.The range of sulfur contents for coals from the Parvadeh coal field (0.37% to 4.64%) and Mazino coal field (0.45% to 2.92%) is related to the effect of marine water in peat.The studied samples are characterized by the predominance of short-over long-chained n-alkanes.The relatively high Pr/Ph ratios indicate predominance of terrestrial organic matter whereas Pr/n-Ci7 and Ph/n-C18 ratios prove oxic conditions during deposition.In addition,the DBT/Phen ratio shows that these coals formed in fluvial/deltaic environments.Molecular geochemical parameters such as carbon preference index (CPI,0.99-1.04),methyl phenanthrene index (MPI,1.20-1.60),methyl naphthalene ratio (MNR,1.61-3.45),and ethyl naphthalene ratio (ENR,4-6.78) confirm the high maturity of the samples.Burial and thermal history reconstruction indicates necessity of an erosional thickness of about 4000 m in the Parvadeh area.Towards the Mazino area,a higher basal heat flow up to 80 mW m-2 is assumed for the Paleogene leading to higher maturities.