Print this page
Sequence
Stratigraphy of the Turonian—Early Campanian Formations in Selected Wells,
Saleem, Sabah N.1,
Mumtaz A. Ameen2 (1) Iraq North Oil Co,
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
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.