Keywords : dolomitization

Environmental Criteria of Stromatolitic Limestones in The Barsrain Formation from Surface Sections, Northeastren Iraq

Mauj Al-Badrani; Rafee Al-Humaidi

Iraqi National Journal of Earth Science, 2019, Volume 19, Issue 2, Pages 80-99
DOI: 10.33899/earth.2019.170279

The rock successions of Barsarin Formation Late Kimmeridgian was studied at three surface sections the type section "17m", Sarglu "19m" and Rania "10m"; northeastern Iraq. The detailed sedimentological study reveals that the formation consists mainly of dolomite and dolomitic limestones. A wide spectrum of diagenetic – processes are recognized in the rock successions; these are dolomitization, compaction, cementation, micritization, dissolution, replacement, neomorphism and silisification. By the far, dolomitization and compaction are the most common and widespread processes. Stromatolites are the dominant primary sedimentary structures in this Formation. Based on field observation and textural characteristics four stromatolite types are distinguished: planar, wavy, domal, and bedded. They are normally formed by carbonates (lime muds) and extensively suffered early dolomitization

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

Rafi I. AL-Homadi; Ibrahim S. Al- Okli

Iraqi National Journal of Earth Science, 2018, Volume 18, Issue 1, Pages 149-164
DOI: 10.33899/earth.2018.159282

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.(.