Lithological Variations and Facies Analysis of the Lower Part of the Bekhme Formation in Specific Outcrops from Dohuk Area, Northern Iraq

Abstract

The present study concerns the sedimentology of the lower part of The Bekhme Formation at the Bekhair anticline, Dohuk area, northern Iraq. This part shows a high spectrum of lithological and petrographical variations of allochthonous and autochthonous carbonate sediments. Accordingly, the formation divides into 3 Facies 1. Random clasts Carbonate Megabreccia . 2. Planktonic Foraminiferal Wackestone. 3. Rounded Clasts Intraformational Carbonate Conglomerate. The facies analysis and their deposition mechanism suggest that the area's deposit environment represents carbonate slope, which was affected by local tectonism of syndepositional normal faulting. The architectural analysis of the sedimentary environment shows that this fault had affected the facies directly, giving considerable variation in the sedimentary environment ( depth, oxygen percent, and bioactivity). These variations are reflected in the carbonate rock types, sedimentary structures, and the early diagenetic processes. The constructed sedimentological model for the basin in this particular environment proposed that this syndepositional normal fault was directly responsible for the type of the carbonate rocks at the lower part of the formation ( the older three facies), and this was reflected by increases in the angle of carbonate slope and also increasing of carbonate sediments mobility towards the half-graben made by the fault. The Bekhme Formation represents part of the main mega sequence (AP9). Within the Late Campanian – Maastrichtian age, This period was characterized by local subsidence caused by secondary normal faults, which are responsible for the formation of the secondary basin. The proposed fault in this study is one of these faults.