Facies architecture and Sequence Stratigraphy of the Lower and Middle Miocene, Kirkuk area, North Iraq

Abstract

The Lower-Middle Miocene in Kirkuk area consists of the Serikagni, Euphrates, Dhiban, Jeribe, and Fat´ha formations. Microfacies analyses reveiled the different subenvironments where the Serikagni Formation(appear only at Ja-26) was deposited in basinal, deep marine, and shallow open marine environments. The Euphrates Formation (Ja-26& Hr-41) reflects restricted marine and shallow open marine deposition. The Dhiban (Ja-26& Hr-41) Formation ( represents sabkha, restricted marine, and shallow open marine environments , The Jeribe Formation (Ja-26, Hr-41& Kz-6) reflects deposition in restricted marine, and shallow open marine environments; in addition to shoal and deep marine environments.The Fat´ha Formatio (appear at all wells) reflects mainly restricted marine, and sabkha environments; in addition to shallow open marine deposition at certain intervals at the top and bottom of the section. Several diagenitic processes affected the studied succession. They include micritization, neomorphism, dissolution, cementation, dolomitize- tion, silisification, compaction, and dedolomitization. In the present study the main effective diagenitic processes are neomorphism, dissolution, cementation, and dolomitization . The studied succession is represented by numerous 5th order cycles at the Fat´ha Formation and 4th order cycles at other formations. These cycles where deposited during successive episodes of relative sea-level rise and stillstands. The nature of these cycles reflected variation in the relative sea level resulted from (eustatic and tectonic subsidence) and consequently the rate of accommodation .