Tectonic Evolution of Southern part of the Mesopotamian Foredeep Basin

Abstract

This study investigated the tectonic evolution of the southern part of the Mesopotamian
Foredeep basin. Subsidence and sedimentation rates were calculated for six oil wells
distributed on the tectonic subzones of the sedimentary basin through the use of restored
thickness rates according to Backstripping Method for Cretaceous and Tertiary sequences. The
consequence of this study indicates the subsidence and sedimentation rates changing vertically
and laterally through geologic time. As shown, the sequences of Albain subcycle are wide
subsidence and sedimentation rates especially for the Mauddud Formation at the Am-1well
which located in the eastern part of the sedimentary basin (Tigris subzone), as well as for the
sequences of Cenomanian-Early Turonian subcycle especially for the Ahmadi and Mishrif
formations were increase in subsidence and sedimentation rate toward (Am-2 and Mj-3) wells.
Both wells located within the Tigris and the eastern part of Zubair subzone. This is in
accordance with the closure of the South Tethys Sea because of the influences of the Austrian
and Subhersynian orogenies. Three unconformity surfaces determine clearly in the depositinal
basin of incompatibility during the Early Turonian, Danian and Oligocene epochs. Those
unconformities affects all tectonic subzones except for the Am-1well where it was not
influences by the unconformity during the Oligocene epoch. The subsidence and sedimentation
process continued at high rates, reflecting the large thickness of the eastern part of the basin in
the Tigris subzone area. Sedimentation rates augment significantly at the well (AG-19), which
indicates the effect of faults on the Tigris subzone. This affects the degree of maturation and
the source of hydrocarbons in the sedimentary basin.