TYPES OF STROMATOLITES IN THE BARSARIN FORMATION (LATE JURASSIC), BARZINJA AREA, NORTHEAST IRAQ

H. Karim, Kamal; S. Daoud, Hyam

	TYPES OF STROMATOLITES IN THE BARSARIN FORMATION (LATE JURASSIC), BARZINJA AREA, NORTHEAST IRAQ
Iraqi Bulletin of Geology and Mining
Article 1, Volume 6, Issue 1, 2010, Pages 31-57
Authors
Kamal H. Karim; Hyam S. Daoud
Abstract
The present study aims to record and describe, for the first time, the occurrence of Barsarin Formation in the Barzinja area (northeast of Iraq) and to provide more details on the limestone succession that contains both laminated and nodular massive beds. Sixty eight samples have been collected from this succession from which more than 68 thin sections have been prepared and studied under binocular and polarized microscopes. Based on the thin sections studies and field observations of outcrops, it is proved that both laminated and massive limestones belong to cryptalgal stromatolite. Morphologically, the examined stromatolites can be divided into four types: Planer, Wavy, Columnar and Spheroidal (oncoidal) stromatolites. The first two types occur as laminated limestone, (mat) while the other two types form more or less massive limestone beds. The formation, as a whole was deposited in a semi-closed lagoon (as a part of rimmed shelf) of an attached carbonate platform, which persisted in a low energy lagoon. The laminated and massive limestones were deposited in protected lagoon within intertidal and subtidal environments, respectively. The lower part suffered from short duration of wave agitation and bioturbation, which are represented by occurrence of rip-up clasts around which oncoids are grown.

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