TYPES OF RECENT MICROBIALITE IN SLIGHTLY ACIDIC SPRING IN RANYIA AREA, KURDISTAN, NE IRAQ

M. Ameen, Bakhtiar; A. Khanaqa, Polla; H. Karim, Kamal

	TYPES OF RECENT MICROBIALITE IN SLIGHTLY ACIDIC SPRING IN RANYIA AREA, KURDISTAN, NE IRAQ
Iraqi Bulletin of Geology and Mining
Article 1, Volume 7, Issue 2, 2011, Pages 27-40
Authors
Bakhtiar M. Ameen; Polla A. Khanaqa; Kamal H. Karim
Abstract
The role of the microbes in precipitation of stromatolitic limestone and lime-sand in water of recent spring in the Kurdistan Region, Northeast Iraq is discussed. The spring mouth is forming a small circular lake (350 m in diameter) with slightly acidic water, and saturated with dissolved CaCO3. Due to effect of the microbes and wind direction (and its related currents), the limestone and lime-sand are deposited mainly on the southwest bank of lake (spring mouth). The role of microbes can be seen in forming many types of the microbial limestones (microbialites), which consist of finely laminated (stromatolite) or clotted structures (thrombolite) or both. The existed stromatolite; forms well developed oncoids of different sizes, and micro-oncoids (ooids), which have diameter of (0.1 – 20) cm. The thrombolite consists of irregular clusters (clotted) of ooids (or micro-oncoids) encrusted by microbial micritic layers and separated by voids. On the lake bank, the small oncoids and thrombolites, which form clotted clusters of ooids mass are exposed on the shore, while large oncoids are exposed away from the shore; on the periodically flooded areas. Both types of limestone and lime-sand show the effect of wind energy in developing the rock with certain types of structure and texture; within the examined rocks, which are analogous with Arabian Gulf.

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