THE TECTONIC AND DEPOSITIONAL EVOLUTION OF THE PALEOZOIC SUCCESSION OF IRAQ

This work is the product of a subsurface study that attempts to characterize the lithofacies, depositional environments, and main tectonic elements affecting the Paleozoic sequences in Iraq. The Paleozoic successions of Iraq are represented by five sedimentary cycles of intracratonic sequences. These sequences are comprised of nine formations, dominated mainly by siliciclastic and mixed sedimentary packages, and are separated by major and minor unconformity surfaces. The study integrates petrographical and lithological data from deep exploration wells and outcrops in northern Iraq to better understand the sedimentary environments present in the basin. These cycles are as follow: the Ordovician cycle, represented by the Khabour Formation; the Silurian cycle, represented by the Akkas Formation; the Middle-Late Devonian to Early Carboniferous cycle, represented by the Chalki, Pirispiki, Kaista, Ora and Harur formations; the Permian-Carboniferous cycle, represented by the Ga'ara Formation and Late Permian cycle, represented by the Chia Zairi Formation. Generally, the studied formations are characterized by siliciclastic and mixed carbonate-clastic facies with abrupt changes during late Paleozoic reflecting the environmental and tectonic instability during this period. The higher thickness of these Paleozoic rocks refers that this shelf was stable during the Paleozoic that gave these successions an important hydrocarbon possibilities. Basin analysis demonstrates the evolution and architecture of the basin and gives an insight into the effects of the Caledonian and Hercynian epeirognic movements on the tectonostratigraphic history of the region.