COAL RANK AND PETROGRAPHY OF UPPER CARBONIFEROUS SEAMS IN THE AMASRA COALFIELD, TURKEY

The Amasra coalfield is a part of the Upper Carboniferous Zonguldak co al basin of Turkey within the Istanbul zone, a Hercynian deformed unit forming the eastern continuation of the Moesian platform in SE Europe which was later deformed by Alpine tectogenesis. The mainly Westphali an aged coals were sampled from an underground mine and from cores fro m nine exploration wells and petrographic (maceral and microlithotype) analysis and mean maximum vitrinite (telocollinite) reflectance (% R- max in oil) were determined. The coals were characterised by low ash a nd low total sulphur contents, abundant vitrinite-group macerals and r elatively abundant vitrite, clarite and duroclarite microlithotypes. V itrinite reflectance was in the range 0.58-1.04% R-max, indicating ran ks from high volatile C bituminous to high volatile A bituminous coal. The % R-max generally increases with increasing depth in the explorat ion wells, with gradients ranging from 0.21 to 0.40% R-max/km and an a verage of 0.30% R-max/km. The highest value occurs in the south of the coalfield in a region of Hercynian folding and thrusting. The relatio nship between vitrinite reflectance and thrusts in the wells suggests that coal rank was developed mainly pre-thrusting but that some wells, arguably, show evidence for post-thrust coalification. Peak coalifica tion probably occurred during Late Mesozoic-Early Tertiary rifting, so that the thrusts which developed after coalification are likely to be Alpine in age whereas the thrusts that pre-date coalification may hav e been Hercynian structures. (C) 1998 Elsevier Science B.V.