POSSIBLE SOURCE ROCKS ON THE TAURIDE CARBONATE PLATFORM: RECORDS OF EQUIVALENT OF CENOMANIAN-TURONIAN ANOXIA AND KIMMERIDGIAN BLACK SHALE IN KONAK-1 WELL (GURUN, SIVAS, CENTRAL TURKEY)

The Konak-1 well is located 120km SE of Sivas city, near the town of Gürün in Central Turkey and cut through the Geyikdagi unit of Tauride Carbonate Platform. Lithostratigraphic and biostratigraphic analysis were carried out on the cutting samples along the whole well.

The well totally covers a 10760 ft thick succession and around 100 samples were analyzed. At the bottom, between 10760 and 9900 ft, thick organic rich mudstone/black shale interval of “Kimmeridgian-Tithonian” in age including alternation of black shale/mudstone, thin limestone, marl and sandstones takes place. This level is overlain by a thick shallow water platform carbonate succession (“Kimmeridgian–Albian” ?) including alternation of dolostone, dolomitic limestone and thick limestones with dasyclad algae and benthic foraminifera between 9900 and 6550 ft. This shallow water carbonate succession is overlain by a marl sequence (“Albian-Turonian”) including alternation of black shale, marl, sandstone and limestone between 6550 and 5500 ft. The marl/black shale levels of “Cenomanian-Turonian” interval may coincide with the Global Oceanic Anoxic Event-2 called Bonarelli Level in European basins. This part of the sequence includes pelagic foraminifera and radiolaria. Therefore, a transgressive or a deepening condition takes place at this part of the carbonate platform.

Overlying succession is composed of alternation of limestone, marl, and occasional glauconitic sandstone between 5500 ft and till the top of the well. This interval was not studied in detail due to less frequent sampling and insufficient cuttings. But, it may also cover interval between upper Cretaceous and lower Tertiary.

The organic rich mudstone/black shale interval of “Kimmeridgian-Tithonian” in age overlain by shallow water carbonates has been interpreted as deposited in an intra-platform trough where anoxic conditions took place.

The “Cenomanian-Turonian” black shale/marl interval has not been properly recognized in the wells and not published on the Tauride carbonate platform before and do not present any outcrop on the surface.

Therefore, in this well, this part of the Geyikdağı Unit of the Tauride Carbonate Platform might have been affected by both regional tectonic movements leading to increased subsidence at the margins and oceanographic events.