AGE DETERMINATION AND ORIGIN OF CRENULATED LIMESTONE IN THE EASTERN PART OF SULAIMAIYAH GOVERNORATE,
KURDISTAN REGION, NE-IRAQ
Imad Mohamood Ghafor, Kamal Haji Karim, and Mushir Mustafa Baziany *1
*1 Department of Geology, University of Sulaimani
Published In: Iraqi Journal of Geology and Mining, Vol.8,No.2,2012
Key words: Said Sadiq town, Kometan Formation, Crenulated limestone, Biostratigraphy, Planktonic foraminifera, Sharazoor plain
Abstract
Many outcrops of crenulated limestones are observed in eastern of Sulaimaniyah city. These limestones are deformed into tight or open mesoscopic folds, which are superimposed on larger-scale synclines or anticlines. The outcrops are discussed and biostratigraphically analyzed. The identified planktoin foraminifera indicated that these limestones belong to Kometan Formation and its age extends from Turonian to late Campanian. The age determination depends on the index planktononic foraminifera; such as Marginotruncana sigali, and Dicarinata imbricate indicate Turonian, Dicarinata primitivae indicate Coniacian, Dicarinata asymmetrica which indicates Santonian and Radotruncana calcarata indicates Early Upper Campanian.
اصل الحجر الجيري المتجعد فى الجزء الشرقي من منطقة السليما نية، شمال شرق العراق
عماد محمود غفور و كمال حاجي كريم و مشير مصطفى البازياني
تم ملا حظة عديد من المكاشف متجعدة للحجر الجيري فى شرقي مدينة السليما نية . ان هذه الصخور متشوهة الى طيات ضيقة او مفتوحة صغيرة الحجم و المتراكبة على طيات اكبر .
من خلال تحليل الطباقية الحياتية للصخور المنكشفة ظهر ان الكاشف ترجع الى تكوين كوميتان. ان المدى الجيولوجى للفورامنيفرا الطافية الوجودة يمتد من التورونين الى الكامبانيان المتاخر. و هذه اعتمادا على الا نواع الدالة من الفورامنيفرا الطافية لعمر التورونين و المتمثلة بالنوعين Dicarinata imbricate و Marginotruncana sigali وكذالك لعمر الكونياسين و المتمثلة بنوع Dicarinata primitivae و لعمر السانتونين و المتمثلة بنوع Dicarinata asymmetrica ولعمر Early Upper Campanian والمتمثلة بنوع Radotruncana calcarata
INTRODUCTION
The eastern part of Sulaimanyia Governorate includes outcrops of crenulated limestone which can be seen sporadically in the eastern and northeastern boundary of Sharazoor Plain in several places especially near Said Sadiq towns. In the present study three localities are inspected and only one of them is sampled (Fig.1). The first place (X1) (sampled one) is located directly to the northwest of Said Sadiq town at the latitude and longitude of N: 35º 21’ 26.25″, E: 45º 51′ 16.13″ (Fig.2). At this locality, the crenulated limestone exists as a large hill which called Ashbolagh hill and it is 130 m high. The second outcrop (X2) is located 2 km to the northwest of Greza village, which forms the peak of the mountain with the same name. The third (X3) is located on the Shinarwe Mountain about 6 km to the east of Halabja town (Fig.1).
The crenulations, in the aforementioned three areas, consist of tight or open mesoscopic folds, which are superimposed on larger-scale syncline (Fig.2). The folding occurred in the well beds of white, fine crystalline limestone. In many places, the axes of the folds are very clear in 3D relief on the surface of the outcrops of the Ashbolagh Mountain (Fig.3). Thin section study showed that the lamination origin is not primary; as it is neither biogenic (stromatolitic) nor physically deposited. It has secondary origin which is developed by pressure and flexure slip during folding.
The stratigraphic origin of these rocks are not known exactly as many authors (such as Sissakian, 2008 and Ali, 2008) mapped the area and not differentiated the carbonate rocks of the early and late Cretaceous formations (Balambo, Dokan, Gulneri and Kometan formations). Bellen et al (1959) cited that Kometan Formation does not exist in the Sirwan Valley. Lithologically, the crenulated limestone is very similar to both Kometan Formations and upper part of the Balambo Formation. The type locality of the Balambo Formation is close to the studied area (about 25 km) and its upper part (as seen by authors) consists of well bedded milky limestone (Fig.4). The aim of this study is to differentiate and separates the crenulated limestone from the other units in the studied area. The methods of the study include field work and collection 100 samples which are regularly sampled and thin sectioned for each sample. The thin sections were inspected under polarized and stereoscopic microscopes.
According to Bates and Jackson (1980), crenulations are small scale folding (wave length up to a few millimeters) that is superimposed on large-scale folding. Crenulations may occur along the cleavage planes of deformed rocks. Richard (1961) mentioned that crenulation cleavage differs essentially from slaty and fracture cleavage it is only developed in laminated rocks and consequently it is always similar to a secondary structure. Variety of planar features form in rocks, these can be conveniently divided into primary and secondary produced as the result of planes. Primary planes are formed when the rocks are deposited, extruded, and included bedding and flow banding. Secondary planes are produced as a result of tectonic processes and include joints, faults, mineral fabrics and metamorphic banding (Price and Cosgrov, 1990). Under polarized microscope very small scale folding can be seen which are developed along the secondary fractures (Fig.5). More than two sets of cross cutting fractures can be seen in some slides.
Fig. 1: Geological map of the study area (modified from Ali, 2008).
Fig. 2: Geologic cross section and Google Earth image of the Ashbolagh hill showing sampled section.
Fig. 3: A) General view of the Ashbolagh hill. B) Close up view showing crenulated limestone.
Fig. 4: Upper part of the type section of the Balambo Formation in Sirwan valley, which is lithologically very similar to Kometan Formation
Fig. 5: Crenulations under polarizer microscope(X40), show a microscopically folded fractures. A) Under XP light shows two phase (dark and light) band of filling of fracture with secondary spary calcite. B) Under normal light shows a folded fracture which cut across a Globotruncana foram
LOCATION AND GEOMORPHOLOGY
The studied area is located in the northeastern part of Iraq in the Eastern part of the Kurdistan Region,and comprises large area of the eastern part of the Sulaimanyia Governorate. It extends between the latitude and 35º 05′ 00″ &35″ 47′ 00″ to the north and longitude 45º12′ 00″ and 46º12’30” to the east. The studied area is mountain encircled basin and located in Iraqi side of Zagros mountain belt, which includes mainly the area that located around Said Sadiq, Khurmal and Halabja vicinities. The area is surrounded from all sides by high mountains while its central part consists of gently inclined flat and intermittently hilly plain. The area is a part of the a Darbandikhan dam watershed and dissected by relatively three large streams of Zalim, Chaqan and Tanjero, which form, with their smaller branches, dendritic drainage pattern.
GEOLOGICAL SETTING OF THE AREA
The studied area is a part of the Zagros mountain belt Governorate (Fig.1). The area is a part of the Western Zagros Fold–Thrust Belts. According to tectonic classification of Buday (1980) and Buday and Jassim (1987), the area is mainly located in the High Folded Zone and partly in the Imbricated Zone. The Thrust Zone, Qulqula Radiolarian Formation and Avroman Group are located directly to the north and northeast of the studied area.
According to Karim, et al. (2009) the area consist of large graben, which is bounded by two normal faults from its eastern and western peripheries. The area is included in the Western Zagros Fold-Thrust Belt which deformed by Laramide and post Laramide Orogenies. During these orogenies, both Iran and Arabian Plates are collided directly at the north of the studied area during the Miocene (Buday, 1980, Al-Qayim, 2000). In this area, the anticlines and synclines are relatively tight and have high amplitudes. Some of them are overturned toward southwest due to the stress of the overriding Iranian Plate. Mainly, all the rocks of the basin are sedimentary which range in the age from Lower Cretaceous (pelagic limestone) Paleocene which includes and clastics rocks as Tanjero and Kolosh Formations (Upper Cretaceous and Paleocene respectively) are exposed in the synclines while the resistive limestones are exposed alonganticlines.
PALEONTOLOGICAL STUDY
More than 50 thin sections were prepared from the collected limestone samples and for identification of the fauna; binocular microscope was used. The following species of planktonic foraminifera are identified in thin sections (Fig.6 and 7).
Radotruncana calcarata (Cushman); Globotruncanita conica (White); Globotruncanita stuarti (de Lapparent); Globotruncanita stuartiformis (Dalbiez); Contusotruncana patelliformis (Gandolfi); Globotruncanella minuta Caron & Gonzales Donoso; Gumbeletria cenomana (Keller); Globotruncana carina Dalbiez; Globotruncana carinata Dalbiez; Globotruncana linueuiana (DOrbigny); Globotruncana bulloides Vogler; Globotruncana ventricosa White; Globotruncana hilli Pessagno; Globotruncana mariei Banner and Blow; Globotruncana fornicata Plummer; Whitenella paradubia (Sigal); Whitenella archaeocretacea Pessagno; Pseudotextularia sp. ; Whitenella baltica Dopuglas & Rankin; Whitenella sp; Dicarinella asymmetrica (Sigal); Dicarinata imbricate (Mornod); Dicarinata primitivae (Dalbiez); Marginotruncana schneegansi (Sigal); Marginotruncana coronata (Bolli); Marginotruncana undulate (Lehmann); Marginotruncana sigali (Reichel); Hedbergella montemonthensis (Olsson); Hedbergella holmdelensis Olsson; Rotalipora cushmani (Morrow); Rotalipora fornicate; Rosta fornicate; Globigerinelloides alvarienzi (Eternod Olvera); Globigerinelloides bolli Pessagno; Globigerinelloides caseyi( Bolli, Loeblich & Tappan); Globigerinelloides bergreeni; Globigerinelloides maridalensis (Bolli) ; Globigerinelloides ultramicrus (Subbotina) ;Globigerinelloides prairiehillensis Pesagno; Rugoglobigerina rugosa (Plummer); Archaeoglobigerina rugosa; Archaeoglobigerina blowi Pessagno; Psudogumbelina costulata (Cushman); Ventilabrella eggeri Cushman; Ventelabrella multicartheta (De Klasz); Heterohelix reussi (Cushman); Heterohelix globulosa; Heterohelix ultimatumida; Heterohelix carinata; Heterohelix moremani (Cushman); Heterohelix punculata; Heterohelix planeta; Heterohelix striata (Ehrenberg); Lavihetrohelix glabrans; Laviheterohelix pulchra; Gansserina wiedenurciyeri; Whitinella baltica Douglas & Rankin. Marginotruncana sigali, and Dicarinata imbricate indicate Turonian, Dicarinata primitivae indicate Coniacian, Dicarinata asymmetrica indicate Santonian, Radotruncana calcarata (Cushman) indicate Late Campanian.
Biostratigraphy
Biostratigraphic study of thin sections is based on the geological range of the identified planktonic foraminifera. Relevantly, Kometan Formation is studied by different authors from 1959 to 2005. Bellen et al, (1959) studied the type section of the formation with Early Turonian-Santonian age, Youkhanna (1976) claimed Turonian- Santonian age, Al–Tameme (1986) studied the Kometan Formation and divided it into 4 biozones of Late Turonian–Early Campanian age. Al–Jassim et al. (1989) studied the Kometan Formation in Northern Iraq and four assemblage zones have been distinguished, which are Turonian–Early Campanian in age. Al-Zaef (1997) studied the formation in Jambour field and claimed Late Turonian–Early Campanian age, Abawi and Hammoudi (1997) studied the biostratigraphy of the Kometan Formation and divided the formation into 5 biozones based on the planktonic foraminifera and indicated Late Turonian–Early Campanian age. Al-Khafaf (2005) studied the Kometan Formation in Dokan area and divided it into 5 biozones based on the identified planktonic foraminifera and claimed Late Turonian–Early Campanian age.
CONCLUSIONS
- Many outcrops of crenulated limestones are observed in the eastern part of the Sulaimaniyah Governorate and discussed petrographically and biostratigraphically.
- The crenulated limestones are rich in planktonic foraminifera and based on the range of these fauna, it is proved that they belong to the Kometan Formation.
- The identified planktonic foraminiferas extend from Turonian to Early Upper Campanian.
- This study is the first to prove (biostrtigraphically) the occurrence of the Kometan Formation in the eastern part of the Sulaimaniyah Governorate.
Fig. 6: a) Globigerinelloides sp., b) Radotruncana calcarata (Cushman), X100,
c) Radotruncana calcarata (Cushman), X100, d) Radotruncana calcarata
(Cushman) X100, d)Radotruncana calcarata (Cushman), e)Radoruncana
calcarata (Cushman) X100, f) Globotruncana linueuiana (D’ Orbigny)
X100, g) Radotruncana calcarata (Cushman) X100.
.
Fig.7: a) Hedbergella montemonthensis (Olsson) X100, b) Globotruncanita conica
(White) X100, c) Heterohelix moremani (Cushman) X100, d) Whitinella baltica Douglas &
Rankin X100, e)Globotruncana ventricosa X100, f)Globotruncana fornicate X100,
g)Marginotruncana coronate X100, h)Rugoglobogerina rugosa X100,
i)Psudotextularia sp. X100, j) Marginotruncan scheenegensis X100–
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