Organic Facies Characteristics of the Miocene Soma Formation (Lower Lignite Succession-KM2), Soma Coal Basin, Western Turkey

The Soma coal basin is one of the largest economic lignite-bearing alluvial basins of western Turkey. The Miocene succession of the coalfield contains two lignite seams successions; Lower Lignite, Middle Lignite. Kerogen in the deposits is type III, as indicated by organic petrographic observations and Rock-Eval data. Total organic carbon (TOC) values are between 28.45 and 73.38% in the formation. Tmax values vary between 403 and 429 C, confirming maturation trends indicated by vitrinite reflectance data (between 0.35-0.48 Ro%). Organic facies type C and CD were identified in the investigated units. The organic matter is partly oxidized/oxidized and reworked.