Sequence Stratigraphy of the Turonian—Early Campanian Formations in Selected Wells, Northeast Iraq

Saleem, Sabah N.¹, Mumtaz A. Ameen² (1) Iraq North Oil Co, Kirkuk, Iraq (2) University of Mosul, Mosul, Iraq

Recognition of depositional sequences using sequence stratigraphic concepts allowed the delineation of three second-order sequences A, B and C in the Gulneri, Kometan and Mushorah Formations in the eastern sector and the equivalent Tanuma, Khasib, Sa’di, and lower Hartha fms. in the western sector of northeast Iraq.

Two third-order sequences were further recognized in Sequence A, and three third-order sequences were recognized in both Sequence B and Sequence C. Each of the third-order sequences is comprised of transgressive and high stand system tracts, while the low stand system tract is restricted to B2, B3, C1 and C2. These system tracts are, in turn, comprised of vertically stacked parasequences of shallowing upward packages.

The derived depositional model is characterized by a flat-top ramp-like geometry initiat­ed from listric normal faults separating highly tilted blocks. The inclined apex continuously eroded to deliver shallow carbonate detritus to basinal sites. Facies associations indicate accumulation in a basin fed by eroded shallow-water derivatives.

The depositional architecture developed in an open marine, middle to outer ramp setting in the Gulneri and Kometan fms. Middle to inner ramp is allocated to the Khasib, Tanuma and lower Hartha fms. Transition to slope setting is conceivable for the Mushorah fm. Slope apron facies are common to all formations, except in the northeast.

Recognition of third-order cycles demonstrates the utility of using genetic unit and sequence stratigraphy to discern depositional architecture. Local tectonic control of sedi­mentation, eustacy, and sedimentation rate are additional determinants for the stratigraphic framework.