--> --> Abstract: Paleocene-Early Miocene Regional Stratigraphic Framework of the Central Mesopotamian Basin and Its Tectonic Implication, by Po C. Tai, George J. Grabowski, Kirk W. Schafer, Chengjie Liu, and Augustus O. Wilson; #90124 (2011)

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Making the Next Giant Leap in Geosciences
April 10-13, 2011, Houston, Texas, USA

Paleocene-Early Miocene Regional Stratigraphic Framework of the Central Mesopotamian Basin and Its Tectonic Implication

Po C. Tai1; George J. Grabowski1; Kirk W. Schafer1; Chengjie Liu1; Augustus O. Wilson2

(1) ExxonMobil Exploration Company, Houston, TX.

(2) Consultant, London, United Kingdom.

The Paleocene-Lower Miocene interval of the Mesopotamian Basin contains important hydrocarbon-producing units in NE Iraq and SW Iran. In the past, the stratigraphic framework of this interval was mainly established and studied based on lithostratigraphy. As a result, different lithostratigraphic names for the same chronostratigraphic unit can be found within a field as well as across fields and country boundaries. The objectives of this work are to re-examine the Paleocene-early Miocene stratigraphy of Iraq and Iran and to further understand its facies distributions. The improved chronostratigraphic framework may provide key constraints on the evolution of the Zagros Foreland Basin system.

Our regional analysis shows that during Paleogene time, two platform margins developed in the Mesopotamian Basin. These two margins prograded toward each other as the basin center was progressively filled by pelagic sediments and evaporites with time. The Eocene sequences are aggradational to progradational whereas the Oligocene sequences display highly progradational and downstepping stacking pattern. The northeastern part of the basin was dominated by a carbonate system with minor amounts of clastics derived from the Zagros fold-thrust belt (ZFTB). The southwestern part of the basin was characterized by a mixed system where the dominant source of clastics was the exposed Shield of Western Arabia. During early Miocene time, subsidence increased significantly and the basin was quickly filled by a thick (2-4 km near the ZFTB) succession of mixed lithologies, including clastics derived from the ZFTB that progressively thins toward the west. The Lower Miocene interval is typically composed of small-scale sequences that are laterally extensive and can be correlated regionally. It shows onlap and erosional truncation across relatively high topographic areas during its deposition.

The Paleocene-Lower Miocene interval of the central Mesopotamian Basin is considered as a part of the Zagros Foreland Basin system. Although the depositional character (i.e., thickness and stratal geometry) of the Miocene interval typifies a foredeep depozone, depositional patterns of the underlying Paleogene are not consistent with expected subsidence behavior in a back-bulge or a distal foredeep depozone dominated solely by orogenic flexure. Additional study is needed to constrain the geodynamic context of the Tertiary depositional systems in the central Mesopotamian Basin.