THE MIOCENE LICE BASIN OF SOUTHEASTERN TURKEY: AN EXAMPLE OF A SHALLOW MARINE TO NON-MARINE FORELAND BASIN

The Lice Formation of Southeastern Turkey is deposited in a shallow-marine Foreland Basin conditions during the Miocene compression and final closure of the Neothesis in the region. This closure is also responsible for the closure of the Miocene to Pliocene seaway between the Eastern Mediterrenean to the East and the Indian Ocean to the West. We have studied the tectonics and sedimentation of the Lice Formation in the Siirt Petroleum District X of South East Anatolia in to better understand a) the Miocene to Pliocene closure and b) hydrocarbon potential of the district containing many oil fields. The Miocene compression is responsible for many structural/stratigraphic features in the region. These features are in turn responsible for the formation of the structural and stratigrafic traps.

We have focused on depositional environments of the Lice Formation in order to understand the structural evolution of the Lice basin. Below the Lice Formation is the shallow marine reefal limestone of the Early Miocene Firat formation which grades vertically and laterally into the shallow marine limestone to sandstone deposits of the Lice formation. The fluvial deposits of the Selmo formation confarmably overlies the Lice Formation. In general, the Lice Formation contains shallow marine shales, marn, sandstone, limestone and nonmarine mudstone, sandstone and gypsum deposits. In Silvan-Selmo area, the Lice Formation is made out of mostly shallow marine limestone interbedded claystone, siltstone, marn and shale. Towards the east, the formaton laterally grades into a non-marine succession containing sandstone, claystone, mudstone, and gypsum. However, in many loactions, the upper contact is truncated with a thrust surface bringing Miocene Allocthnous rocks over the Lice Formation. The thrust is usually used the gypssuim beds of the Lice Formations and thrusting surface.

Although many Miocene Alpine and Himalayan Foreland Basins contain deep marine shales as potential source rocks for hydrocarbon exploration, Lice basin appears not to deep enough to deposit large amount of organic-rich shale deposits. However, the Miocene allocthonous rocks may have provided enough burial to serve as source rock for shale deposits of the Lice Formation although they are very rich in organic content.