Microfacies Analysis And Depositional Environment Of Pila Spi Formation (Middle - Late Eocene) In The Nerwa Section, Berat Anticline, High Folded Zone, Kurdistan Region, Northern Iraq

Q3 Earth and Planetary Sciences Bulletin of the Geological Society of Malaysia Pub Date : 2022-05-23 DOI:10.7186/bgsm73202212
I. Asaad
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引用次数: 2

Abstract

Microfacies analysis and depositional environment of the Pila Spi Formation (Middle-Late Eocene) were studied in the Nerwa outcrop, Berat anticline, High Folded Zone in Iraqi Kurdistan Region. The total thickness of the formation is 13.5 m composed of medium to thick bedded yellow to white limestone and thick bedded grey to white dolomitic limestone. It is interbedded with thin beds of yellow marl in the lower part and have chert nodules in the upper part. The petrographic study of 17 thin sections of the Pila Spi carbonate showed that the majority of the carbonates are micritic mixed with some microspar. The skeletal grains involve benthonic foraminifera, ostracods, mollusca, dasycladacean green algae, pelecypods, gastropods, rare planktonic foraminifera and bioclasts. Non skeletal grain included peloids, intraclasts and extraclasts which is mainly monocrystalline quartz grain. Based on field observations and petrographic analysis, three different lithological units were distinguished in the Pila Spi Formation in the studied section. They are in ascending order: medium to thick bedded limestone interbedded with marl unit, thick bedded dolomitic limestone unit and, cherty limestone unit. Depending on detailed microfacies analysis of carbonate rocks, three main microfacies and twelve submicrofacies were recognized in the studied section of the Pila Spi Formation. From the sum of all petrographic, facies and textural analyses, it is here concluded that Pila Spi Formation in the Nerwa section was deposited at subtidal semi-restricted lagoon, in lower part gradually changed to open lagoon environment toward the upper part.
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伊拉克北部库尔德斯坦地区高褶皱带Berat背斜Nerwa剖面Pila Spi组(中-晚始新世)微相分析及沉积环境
研究了伊拉克库尔德斯坦地区高褶皱带Berat背斜Nerwa露头Pila Spi组(始新世中晚期)的微相分析和沉积环境。该地层的总厚度为13.5 m,由中厚层黄色至白色石灰岩和厚层灰色至白色白云质石灰岩组成。下部为黄色泥灰薄层夹层,上部为燧石结核。对Pila Spi碳酸盐岩的17个薄片进行的岩相研究表明,大多数碳酸盐岩是混有一些微相的微晶。骨骼颗粒包括底栖有孔虫、介形虫、软体动物、大环目绿藻、佩莱脚类、腹足类、稀有浮游有孔虫和生物碎屑。非骨粒包括球粒、晶内粒和晶外粒,主要为单晶石英粒。根据现场观测和岩相分析,在研究剖面中的Pila Spi组中区分出三种不同的岩性单元。它们按升序排列:中厚层状石灰岩与泥灰岩单元互层,厚层状白云质石灰岩单元和燧石质石灰岩单元。通过对碳酸盐岩微相的详细分析,在研究剖面中识别出三个主要微相和十二个亚微相。从所有的岩相和结构分析的总和来看,Nerwa剖面的Pila Spi组沉积在潮下半限制性泻湖中,下部逐渐向上部转变为开放性泻湖环境。
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来源期刊
Bulletin of the Geological Society of Malaysia
Bulletin of the Geological Society of Malaysia Earth and Planetary Sciences-Earth and Planetary Sciences (miscellaneous)
CiteScore
1.60
自引率
0.00%
发文量
15
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