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

Sardar M. Balaky , Rzger A. Abdula and Edres M. Perot
Department of Petroleum Geosciences, Soran University, Soran, Kurdistan Region, Iraq


Abstract

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.

Key Words:
Facies
Carbonate
Garagu
Lagoon
Gara Mountain
Kurdistan


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