Biostratigraphy of dokan, gulneri, and lower part of komeatn formations from kosrat anticline, sulaimani area, kurdistan REGION-IRAQ

Abstract EN

The planktic foraminiferal assemblages were recorded from the Cenomanian/ Turonian boundary from the outcrops section in Kosrat anticline (NE of Dokan dam), within the high folded-thrust zone (Sulaimani area, Kurdistan Region, Iraq).

They are assigned to the Middle Late Cenomanian Rotalipora cushmani partial Zone and to the lowermost Turonian Whiteinella archaeocretacea partial range Zone, in addition to the late Turonian age represented by Helvetoglobotruncana helvetica have been recorded across the Cenomanian/ Turonian boundary, where the early cretaceous platform developed into Kurdistan Foreland basin, as result of the initial phase of Arabian plate subduction beneath the Iranian (Eurasian) Plate.

The high-resolution foraminiferal biostratigraphic analysis has been undertaken on the Dokan Formation, Gulneri Formation, and lowermost part of the Kometan Formation, almost revealing a minor gap between the latest Cenomanian and Early Turonian, as well as between the Ealy Turonian and the late Turonian age.

The termination of Early cretaceous inner ramp (Rudists) carbonate facies associations by the middle to late Cenomanian represents by the uppermost stromatolite beds of the Qamchuqa Formation.

They are overlain by rapid drowning, which is characterized by Planktic bathyal facies association with Dokan Formation.

The increase in drowning is associated with the deposition of organic-rich black shale of the Gulneri Formation with a remarkable short-term gap between them.

The thin black shale, which is sandwiched between the early and late carbonates sequences, almost shows a diagnostic shift in the planktic foraminiferal associations and marks the Cenomanian - Turonian Boundary Event (93.9 Ma).

They are also characterized by abnormal carbon cycle perturbations in Earth's history and associated with oxygen deficiency in oceanic waters (Oceanic Anoxic Event 2 = OAE 2), in Kurdistan and northern Iraq.