ABSTRACT: Geologic Evolution of the Kastel Trough and its Implications on the Adiyaman Oil Fields, SE Turkey

Bulent Coskun

Oil field developments of the Adiyaman area, one of the main oil-producing zones in southeast Turkey, have been highly influenced by geologic evolution of the Kastel trough, which is situated in front of the suture zone between the Arabian and Anatolian plates. The Upper

Cretaceous movements created many paleostructural trends in the Kastel trough where important dolomitic and porous reservoirs exist. The most important tectonic event, which appeared during the Upper Cretaceous movements, is the accumulation of the Kocali-Karadut ophiolitic complex, advancing from the north to the south in the Kastel trough, where heavy materials caused formation of a structural model favoring generation and migration and entrapment of oil in the reservoir rocks. Due to the presence of the Kocali-Karadut complex in the Kastel trough, the following zones have been distinguished.

(1) North Uplift Area. Situated under the allochthonous units, many thrust and reverse faults characterize this zone. The presence of paleohighs, where primary dolomites develop, allows the appearance of some oil fields in the region. This is the main future exploration zone in southeast Turkey.

(2) Accumulation Area. Advancing from the north to the south, the allochthonous Kocali-Karadut complex filled the Kastel trough, creating a deep graben whose flanks present generally normal faults.

(3) Structural Belt. Important paleohighs constitute an exploration trend in this zone where dolomitic and porous carbonates contain actual oil fields.

(4) South Accumulation Area. Distant from the Arabian-Anatolian suture zone, regional tectonics and sedimentology show this zone remained deeply buried during geologic time; good source rocks were deposited during the Cretaceous.

(5) South Uplift Area. This area corresponds to the northern flank of the huge regional Mardin high in southeast Turkey where new oil fields have been discovered.

Surface and subsurface interpretations indicate that the tectono-sedimentary evolution of the Kastel trough favored oil occurrence in the Adiyaman area in southeast Turkey.

AAPG Search and Discovery Article #91003©1990 AAPG Annual Convention, San Francisco, California, June 3-6, 1990