Diagenesis processes of the Gulneri Shale, Kometan, Mushorah formations within the upper Turonian - lower Campanian Supersequence from Bai Hassan area, North of Iraq

Abstract

The upper Turonian - lower Campanian Supersequence is characterized with fine-grained, mixed siliciclastic-carbonate middle shelf to sub-basinal depositional system. The present study included the study of vertical and lateral changes of the diagenesis processes of the Gulneri shale, Kometan and Mushorah Formations within the sequences of the (upper Turonian-lower Campanian) cycle in two subsurface sections within the Dome of Daoud in the Bai Hassan field - northern Iraq. The first is represented by a section (BH-16) with a thickness of (213) m. In contrast, the second is represented by a section (BH-86) and a thickness of (233) m. The lithostratigraphy of the rock units of this study are consisting (206) slides were studied, (80) for well (BH-16) and (126) for well (BH-86).The study showed that the sequences of this cycle are unconformity with the lower Dokan Formation and upper contact with Hartha. The petrographic study showed that the rocks of the study were exposed to many diagenesis processes, like cementation, dolomitization, neomorphism, dissolution and compaction according to the degree of their prevalence with a large spread of locally authigenic minerals represented by the widespread pyrite mineral during the two sections of the study, in addition to a few presence of glauconite mineral. Depending on the petrographic description of the diagenesis processes, the vertical and lateral changes of the diagenesis processes were studied, and the diagenesis environments of the formations under study were deduced, where it was found that all the rocks of the two sections of the study were formed in the early stages of the diagenesis processes within the vadose environments as a result of exposure to tectonic processes that helped uplift their rocks to the surface and be affected by meteoric water.