The facies analysis and sequence stratigraphy of Albian Santonian succession of Surdash- Shaqlawa and Kirkuk area, NE. Iraq
Maher Mandeel Mahdi
Seven outcrops that extend from Surdash to Shaqlawa cities were studied. These outcrops were deposited during the Albian to Santonian. They comprise the Qamchuqa contact, Dokan, Gulneri, Kometan Formations and Shiranish Formation contact. Additionally, five subsurface sections were chosen for supporting the outcrops. These sections are the BH-90, BH-134, BH-138, K-246 and K-260. Four microfacies and thirteen submicrofacies were identified. The microfacies and lithology for the studied area are indicated little variation in microfacies, may change slightly, but the overall setting remains constant for each formation. Packstone microfacies represent the most common microfacies in present study. These microfacies determine the depositional environments. The Dokan Formation was deposited in open-marine deep shelf environment. The Gulneri Formation deposited in open sea shelf and outer shelf settings. The Kometan Formation represent pelagic sediments characterize the deep-marine basins in open marine. The diagenetic features emphases that a burial environment is the frequent environment in the present study.
Basin analysis is carried out on the Cretaceous to Tertiary succession in five wells within the Kirkuk and Bai Hassan Oil Fields. The Foothill Zone exhibited a complex subsidence and uplift history over a period of about 132 Ma. The results from the studied wells backstripping provide a record of the subsidence and uplift history in a number of important Meso-Cenozoic depositional successions. The results show three distinct episodes separated by unconformity surfaces. The value of compaction varies from large during the Cretaceous period to less clearly during the Paleogene and then almost non-existent during the Neogene. Generally, the subsidence is continuous and gradual during the Mesozoic and suddenly increases in the Cenozoic with obvious effect to the tectonic movements. The Bai Hassan Oil Field is affected by the tectonism more than Kirkuk Oil fields during the Cretaceous and continuous to the Recent. The sequence stratigraphy study reveals three third orders. Sequence -A represent the complete section of the Dokan and lower part of the
The sequence stratigraphy study reveals three third orders. Sequence -A represent the complete section of the Dokan and lower part of the Gulneri Formations. The age of this sequence is Middle Cenomanian. Sequence- B includes the upper part of the Gulneri and lower part of the Kometan Formations the age of this sequence is Early Cenomanian to Early Turonian. . Sequence -C represents the remaining part of the Kometan Formation. It represents the longest age and largest thickness because of the stability of the sea level with the less effect of the tectonic movement. The age of this sequence is Turonian to Santonian. The suggested sedimentary and tectonic model reveals some facts: Qamchuqa Formation is deposited within lower unit of trinity underfilled while the Dokan,
The suggested sedimentary and tectonic model reveals some facts: Qamchuqa Formation is deposited within lower unit of trinity underfilled while the Dokan, Gulneri, Kometan and Shiranish Formations are within middle unit and Tanjero Formation is within lower unit. The succession in some surface sections is invalid from one or two of the studied formations because of the existence of the differential faults in the forebulge depozone. Whereas, the studied formations in Kirkuk embayment (oil wells) have complete succession, because they occur far away from forebulge depozone, which lie within back-bulge depozone that be less effected in faults and uplift, this conclusion is proved by basin analysis results.