Facies Analysis and Depositional Environment of Garagu Formation (Valanginian- Hauterivian) in Gara Mountain, Gali Garagu, Sarsang District, Iraqi Kurdistan Region

Volume 1 , Issue 1 , January 2016 , Pages 51-67

Authors

¹ Department of Petroleum Geosciences, Soran University, Soran, Kurdistan Region, Iraq

Facies analysis and depositional environment of Garagu Formation (Valanginian-

Hauterivian) in the Gara Mountain in Gali Garagu of High Folded Zone, Sarsang

District, and northern Iraqi Kurdistan is studied. Lithologically, the formation consists of

oolitic sandy limestones, with shale, marl and sandstones in its upper and lower parts and

organic detrital limestones in its middle part. The petrographic study of carbonate rocks

on 30 thin sections shows that the limestones are dominated by mudstones and

wackestones.The skeletal grains include variety of benthic foraminiferas, gastropods,

brachiopods, echinoids, pelecypods, green algae, and ostracods. Non-skeletal grains

include ooids, peloids and intraclasts. Garagu sandstones are immature, lithic subarkose

to subarkose and occur as medium to thick beds within the lower and upper parts of the

formation, and composed mainly of sedimentary rock fragments with minor amount of

quartz and feldspars (plagioclase). The X-ray diffraction analysis of the bulk shale

samples revealed that the abundant clay mineral in Garagu Formation is kaolinite and

non-clay minerals include calcite, quartz, geothite and nacirite. The formation can be

divided into three lithologic devisions from base to top: lower oolitic; middle organic

detrital limestone; and upper oolitic. Eight different microfacies were recognized which

were subdivided according to their environmental interpretation into two basic types of

facies associations; shelf margin (shoal) and shelf lagoon association. Generally the

Garagu Formation represents shallow water environment with two high energy belts in

the lower and upper parts.

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