The Effect of Dolomitization on Mergi Formation Sequences (Cenomanian- Early Turonian ) at The Type Section, Northern Iraq

Abstract

In order to study the effect of dolomitization on Mergi Formation sequences (Cenomanian – Early Turonian), Field and petrographical examinations were carried out on fourty six meters (46m) of the type section of this formation. It has been observed that the formation is highly affected by diagenesis processes, especially dolomitization. On the other hand, the effects of other processes such as. cementation, dissolution, micritization and compaction in its both types, physical and chemical were less than dolomitization. Dolomite crystals appeared as rhomb-shaped euhedral to subhedral. The main diagnosed fabrics were Aphanotopic, Contact-rhomb porpherotopic, fogged mosaic, Sutured mosaic, Saddle dolomite and Cloudy-centered clear-rimmed dolomite fabrics. It is concluded that formation of dolomite was by the mechanism of mixing zone model and subsurface dolomitization model.(.