341 Al-Nuaimi and Al-Badrani Bull. Iraq nat. Hist. Mus. (2021) 16 (3): 341-358. https://doi.org/10.26842/binhm.7.2021.16.3.0341 CALCAREOUS NANNOFOSSILS BIOSTRATIGRAPHY OF JADDALA FORMATION IN WELL (AJEEL-10), CENTRAL IRAQ Israa Sabah Al-Nuaimi* and Omar Ahmed Al-Badrani* *Department of Geology, College of Science, Mosul University, Iraq. *Corresponding author email: omarbadrani@uomosul.edu.iq Received Date: 11 February 2021, Accepted Date: 24 May 2021, Published Date: 20 Jun 2021 ABSTRACT A detailed systematic study of calcareous nannofossils was carried out for the Jaddala Formation in (Aj-10) well, Central Iraq. Seventy one species belong to twenty four genera of calcareous nannofossils were identified including sixty two of them were previously named and nine species were identified for the first time and they would not be given names until more information is obtained in the future to support this identification. It is a recorded of five biostratigraphic zone, which suggested the age of the Jaddala Formation to be of early to late Eocene. The recorded biozone includes the following: Reticulofenestra dictyoda (Deflandre in Deflandre & Fert, 1954) Stradner & Edwards, 1968 Partial Range Biozone (CNE 5); Discoaster sublodoensis Bramlette and Sullivan, 1961 Interval biozone (CNE 6-7); Nannotetrina cristata (Martini, 1958) Perch-Nielsen, 1971 Interval biozone (CNE 8); Nannotetrina alata (Martini in Martini & Stradner, 1960) Haq and Lohmann, 1976 Interval biozone (CNE 9); Chiasmolithus gigas Bramlette & Sullivan, 1961Range Biozone (CNE 10-11). Keywords: Biostratigraphy, Calcareous, Eocene, Iraq, Jaddala, Nannofossils. INTRODUCTION The Jaddala Formation was first described by Henson in 1940 near Jaddala village in north Iraq (Bellen et al., 1959). The Jaddala Formation outcrops showed up on narrow area of the Foothill Zone of Sinijar Mountain in the Northwestern of Iraq. It was occupied most of sediments in north areas during Eocene period and observed in most of subsurface sections with different thicknesses. The studied section from Ajeel well No. (10) is located 34º 50ʹ 14.8ʺ N. and 43º 53ʹ 59.0ʺ E, North East of Tikrit City, Central Iraq (Map.1), within the Low Folded Zone belonging to Unstable Shelf of the Nubio-Arabian platform (Buday and Jassim, 1987). The sampled stratigraphic succession of the Jaddala Formation in this well (15 samples) consists of marly limestone. https://doi.org/10.26842/binhm.7.2021.16.3.0341 342 Calcareous nannofossils biostratigraphy of Jaddala The stratigraphic succession of the Eocene in Iraq was studied based on the calcareous nannofossils by many authors such as Al-Badrani (2007); Al-Badrani (2011); Al-Badrani and Al-Nima (2010); Al-Badrani and Al-Ubaidi (2012) and Al-Badrani and Al-Zubaidi (2015, 2017, 2019 a and b). The aim of the present work is to determine the age of the Jaddala Formation by using calcareous nannofossils. MATERIALS AND METHODS A detailed study of calcareous nannofossils was carried out for stratigraphic successions of Jaddala Formation which is about 68m and consists of marly limestone, overlies Aaliji Formation and underlies Oligocene Group. Fifteen cutting samples were used and examined under the light microscope. The extracted calcareous nannofossils were identified by using the Armstrong and Brasier (2005) methods for paleontological studies. It is an extraction method for microfossils that can be properly examined when it is extracted from the rocks. The sample preparation included smear slides preparation which provides method for producing slides of calcareous nannofossils by placing a small amount of the disaggregated sample in distilled water and a drop of a dispersant. Then, the cover slip was left to dry on a warm hot plate. And to make permanent mounts, the slide and residue were allowed to dry at a low temperature away from possible sources of contamination. Finally, a drop of mounting medium (e.g. Canada balsam) was placed on a clean cover slip which in turn placed over the residue. Then, it was allowed to dry before examining under the transmitted light. Map (1): Tectonic map of Iraq showing studied section (Jassim and Goff, 2006). 343 Al-Nuaimi and Al-Badrani RESULTS AND DISCUSSION The aim of the systematic classification is to provide images of the notable calcareous nannofossils from the Tanjero Formation in Azmeranticline, Northern Iraq and to describe the seventy one species. All the observed taxa are listed below (Diag. 1). The higher taxonomy essentially follows the scheme of Young and Bown (1997) in addition to Perch-Nielsen's (1985). The material and images are stored at the Department of Geology, Science College, University of Mosul. (A) Systematic and Classification I-Heterococcoliths Family: Helicosphaeraceae Black, 1971 Genus: Helicosphaera Kamptner, 1954 Helicosphaera ampliaperta Bramlette & Wilcoxon, 1967(Pl.1a) Helicosphaera compacta Bramlette & Wilcoxon, 1967(Pl.1b) Helicosphaera lophota Bramlette & Sullivan, 1961 (Pl.1c) Helicosphaera papillata Bukry & Bramlette, 1969 (Pl.1d) Helicosphaera reticulata Bramlette & Wilcoxon, 1967(Pl.1e) Helicosphaera salebrosa Perch-Nielsen, 1971 (Pl.1f) Helicosphaera seminulum Bramlette & Sullivan, 1961(Pl.1g) Helicosphaera wilcoxonii (Gartner, 1971) Jafar & Martini, 1975 (Pl.1h) Helicosphaera sp. (Pl.1i) Family: Pontosphaeraceae Lemmermann, 1908 Genus: Pontosphaera Lohmann, 1902 Pontosphaera distincta (Bramlette & Sullivan, 1961) Roth &Thierstein, 1972(Pl.1j) Pontosphaera fimbriata ( Bramlette & Sullivan, 1961) Romein, 1979(Pl.1k) Pontosphaera multipora (Kamptner, 1948) Roth, 1970(Pl.1 l) Pontosphaera ocellata (Bramlette & Sullivan, 1961) Perch - Nielsen, 1984(Pl.2a) Pontosphaera plana (Bramlette & Sullivan, 1961) Haq, 1971(Pl.2b) Pontosphaera scissura (Perch - Nielsen, 1971) Romein, 1979(Pl.2c) Genus: Transversopontis Hay, Mohler & Wade, 1966 Transversopontis prava Locker, 1967(Pl.2d) Transversopontis sp. (Pl.2e) Family: Zygodiscaceae Hay & Mohler, 1967 Genus: Lophodolithus Deflandre in Defalndre & Fert, 1954 Lophodolithus nascens Bramlette & Sullivan, 1961(Pl.2f) Genus: Nannotetrina Achuthan & Stradner, 1969 Nannotetrina alata (Martini in Martini & Stradner, 1960) Haq & Lohmann, 1976(Pl.2g) Nannotetrina cristata (Martini, 1958) Perch - Nielsen, 1971(Pl.2h) Nannotetrina quadrata (Bramlette & Sullivan, 1961) Bukry, 1973(Pl.2i) 344 Calcareous nannofossils biostratigraphy of Jaddala Family: Rhabdosphaeraceae Lemmermann, 1908 Genus Blackites Hay & Towe, 1962 Blackites inflatus (Bramlette & Sullivan, 1961) Kapellos & Schaub, 1973 (Pl.2 j) Blackites piriformis (Pavsic in Khan et al., 1975) Aubry, 1999 (Pl.2 k) Blackites singulus Bown and Jones, 2006 (Pl.2 l) Blackites sp. (Pl.3a) Family: Coccolithaceae Poche, 1913 Genus: Chiasmolithus Hay, Mohler & Wade, 1966 Chiasmolithus gigas Bramlette & Sullivan, 1961(Pl.3b) Chiasmolithus grandis (Bramlette & Riedel, 1954) Radomski, 1968(Pl.3c) Genus: Coccolithus Schwarz, 1894 Coccolithus crassus Bramlette & Sullivan, 1961(Pl.3d) Coccolithus pelagicus (Wallich, 1877) Schiller, 1930(Pl.3e) Coccolithus sp. (Pl.3 f) Genus: Cruciplacolithus Hay & Mohler in Hay et al., 1967 Cruciplacolithus frequens (Perch - Nielsen, 1977) Romein, 1979(Pl.3 g) Genus: Erocsonia Black, 1964 Erocsonia formosa (Kamptner, 1963) Haq, 1971(Pl.3 h) Family: Noelaerhabdaceae Jerkovic, 1970 Genus: Cyclicargolithus Bukry, 1971 Cyclicargolithus floridanus (Roth & Hay in Hay et al., 1967) Bukry, 1971c (Pl.3 i) Cyclicargolithus abisectus (Muller, 1970) Wise, 1973 (Pl.3 j) Genus: Dictyococcites Black, 1967 Dictyococcites bisectus (Hay, Mohler & Wade, 1966) Roth, 1970(Pl.3 k) Dictyococcites scrippsae Bukry and Percival, 1971(Pl.3 l) Genus: Reticulofenestra Hay, Mohler & Wade, 1966 Reticulofenestra dictyoda (Deflandre in Deflandre & Fert, 1954) Stradner in Stradner & Edwards, 1968 (Pl.4 a) Family: Prinsiaceae Hay & Mohler, 1967 Genus: Prinsius Hay & Mohler, 1967 Prinsius bisulcus (Stradner, 1963) Hay & Mohler, 1967(Pl.4 b) Genus: Toweius Hay & Mohler, 1967 Toweius occultatus (Locker, 1967) Perch - Nielsen, 1971(Pl.4 c) Toweius pertusus (Sullivan, 1965) Romein, 1979(Pl.4 d) 345 Al-Nuaimi and Al-Badrani Family: Papposphaeraceae Jordan & Young, 1990 Genus: Thoracosphaera Kamptner, 1927 Thoracosphaera saxae Stradner, 1961(Pl.4 e) II– Holococcoliths Family: Calyptrosphaeraceae Boudreaux & Hay, 1969 Genus: Zygrhablithus Deflandre, 1959 Zygrhablithus bijugatus (Deflandre in Deflandre & Fert, 1954) Deflandre, 1959(Pl. 4 f) Zygrhablithus sp. (Pl.4 g) III– Nannoliths Family: Braarudosphaeraceae Deflandre, 1947 Genus: Br Braarudosphaera bigelowii (Gran & Braarud, 1935) Deflandre, 1947(Pl.4 h) Braarudosphaera discula Bramlette & Riedel, 1954 (Pl.4 i) Braarudosphaera stylifera Troelsen & Quadros, 1971(Pl.4 j) Braarudosphaera sp. (Pl.4 k) Genus: Micrantholithus Deflandre, 1950 Micrantholithus pinguis Bramlette & Sullivan, 1961(Pl.4 l) Micrantholithus sp. (Pl.5a) Family: Discoasteraceae Tan, 1927 Genus: Discoaster Tan, 1927 Discoaster adamanteus Bramlette & Wilcoxon, 1967(Pl.5 b) Discoaster deflandrei Bramlette & Riedel, 1954 (Pl.5 c) Discoaster floreus Bystricka, 1964 (Pl.5 d) Discoaster germanicus Martini, 1958 (Pl.5 e) Discoaster kuepperi Stradner, 1959 (Pl.5 f) Discoaster martinii Stradner, 1959 (Pl.5 g) Discoaster nodifer (Bramlette & Riedel, 1954) Bukry, 1973(Pl.5 h) Discoaster saipanensis Bramlette & Riedel, 1954(Pl.5 i) Discoaster sublodoensis Bramlette & Sullivan, 1961 (Pl.5 j) Discoaster triangularis Bystricka, 1966(Pl.5 k) Discoaster trinus Stradner, 1961(Pl.5 l) Discoaster sp. (Pl.6 a) Family: Heliolithaceae Hay & Mohler, 1967 Genus: Heliolithus Bramlette & Sullivan, 1961 Heliolithus cantabriae Perch-Nielsen, 1971(Pl.6 b) Family: Lithostromationaceae Deflandre, 1959 Genus: Rhomboaster Bramlette & Sullivan, 1961 Rhomboaster cuspis Bramlette & Sullivan, 1961(Pl.6 c) http://www.nhm.ac.uk/hosted_sites/ina/taxcatalog/cenozb.htm 346 Calcareous nannofossils biostratigraphy of Jaddala Genus: Tribrachiatus Shamrai, 1963 Tribrachiatus contortus (Stradner, 1958) Bukry, 1972(Pl.6 d) Family: Sphenolithaceae Deflandre, 1952 Genus: Sphenolithus Deflandre, 1952 Sphenolithus arthurii Bown, 2005 (Pl.6 e) Sphenolithus editus Perch - Nielsen in Perch - Nielsen et al., 1978 (Pl.6 f) Sphenolithus obtusus Bukry, 1971a (Pl.6 g) Sphenolithus primus Perch-Nielsen, 1971(Pl.6 h) Sphenolithus pseudoradians Bramlette & Wilcoxon, 1967(Pl.6 i) Sphenolithus radians Deflandre in Grasse, 1952(Pl.6 j) Sphenolithus sp. (Pl.6 k) Diagram (1): Percentage of studied calcareous nannofossils taxa; (a) calcareous nannofossils groups, (b) Heterococcolithus families, (c) Holococcoliths families, (d) Nannoliths families. 347 Al-Nuaimi and Al-Badrani Plate (2): Cross-polarized and light photos of significant calcareous nannofossil taxa from Jaddala Formation. (a) Pontosphaera ocellata, (b) P. plana, (c) P. scissura, (d) Transversopontis prava, (e) Transversopontis sp.,(f) Lophodolithus nascens, (g) Nannotetrina alata,(h) N. cristata, (i) N. quadrata, (j) Blackites inflatus, (k) B. piriformis, (l) B. singulus. (Scale bar: 5 micron). Plate (1): Cross-polarized photos of significant calcareous nannofossil taxa from Jaddala Formation; (a) Helicosphaera ampliaperta, (b) H. compacta, (c) H. lophota, (d) H. papallata, (e) H. reticulate, (f) H. salebrosa, (g) H. seminulum, (h) H. wilcoxonii, (i) Helicosphaera sp., (j) Pontosphaera distincta, (k) P. fimbriata,(l) P. multipora. (Scale bar: 5 micron). 348 Calcareous nannofossils biostratigraphy of Jaddala Plate (3): Cross-polarized and light photos of significant calcareous nannofossil taxa from Jaddala Formation; (a) Blackites sp., (b) Chiasmolithus gigas, (c) C. grandis, (d) Coccolithus crassus,(e) C. pelagicus, (f) Coccolithus sp.,(g) Cruciplacolithus frequens, (h) Erocsonia formosa, (i) Cyclicargolithus floridanus, (j) C. abisectus, (k) Dictyococcites bisectus, (l) D.scrippsae. (Scale bar: 5 micron) Plate (4): Cross-polarized photos of significant calcareous nannofossil taxa from Jaddala Formation; (a) Reticulofenestra dictyoda,(b) Prinsius bisulcus, (c) Toweius occultatus, (d) T. pertusus, (e) Thoracosphaera saxae, (f) Zygrhablithus bijugatus, (g) Zygrhablithus sp., (h) Braarudosphaera bigelowii, (i) B. discula, (j) B. stylifera, (k) Braarudosphaera sp.,(l) Micrantholithus pinguis. (Scale bar: 5 micron). 349 Al-Nuaimi and Al-Badrani Plate (5): Cross-polarized and light photos of significant calcareous nannofossil taxa from Jaddala Formation; (a) Micrantholithus sp., (b) Discoaster adamanteus, (c) D. deflandrei, (d) D. floreus, (e) D. germanicus, (f) D. kuepperi, (g) D. martini, (h) D. nodifer, (i) D. saipanensis, (j) D. sublodoensis, (k) D. triangularis, (l) D. trinus. (Scale bar: 5 micron). Plate (6): Cross-polarized and light photos of significant calcareous nannofossil taxa from Jaddala Formation; (a) Discoaster sp., (b) Heliolithus cantabriae, (c) Rhomboaster cuspis, (d) Tribrachiatus contortus, (e) Sphenolithus arthurii, (f) S. editus, (g) S. obtusus, (h) S. primus, (i) S. pseudoradians, (j) S. radians, (k) Sphenolithus sp.. (Scale bar: 5 micron). 350 Calcareous nannofossils biostratigraphy of Jaddala B-Nannobiostratigraphy 1- Reticulofenestra dictyoda Partial Range Biozone (CNE 5) Definition: Partial range biozone of Reticulofenestra dictyoda. Boundaries: The biozone is determined by the last occurrence of Tribrachiatus orthostylus, to the first occurrence of Discoaster sublodoensis. Thickness: Between (1265-1250) m. depths. Correlation and Discussion: This biozone is correlated to the biozone NP13 which was studied by Martini (1971) aged of the Early Eocene (Ypresian) and to biozone CP11which was studied by Okada and Bukry (1981) aged of the Early Eocene (Y prsian). This biozone corresponds to biozne CNE 5 which was studied by Agnini et al. (2014) aged of the Early Eocene (Y prsian); therefore; Early Eocene was suggested in this study. (Gradstein et al., 2012) (Diags.1-3). 2 – Discoaster sublodoensis Interval biozone (CNE 6-7) Definition: Interval biozone of Discoaster sublodoensis. Boundaries: The biozone is determined by the first occurrence of Discoaster sublodoensis to the first occurrence of Nannoterina cristata. Thickness: Between (1250-1240) m. depths. Correlation and Discussion: This biozone is correlated to the lower biozone of NP14 which was studied by Martini (1971) aged of the Early Eocene(Y presian) and to Subbiozone CP12a which studied by Okada and Bukry (1981) aged of the Early Eocene (Yprsian). This biozone corresponds to bioznes CNE 6 and 7 which was studied by Agnini et al. (2014) aged of the Early Eocene (Y prsian), therefore, Early Eocene was suggested in this study as well (Gradstein et al., 2012) (Diags.1-3). 3 – Nannotetrina cristata Interval biozone (CNE 8) Definition: Interval biozone of Nannotetrina cristata. Boundaries: The biozone is determined by the first occurrence of Nannotetrina cristata to the first occurrence of Nannotetrina alata. Thickness: Between (1240-1225) m. depths. Correlation and Discussion: This biozone is correlated to the upper biozone of NP14 which was studied by Martini (1971) aged of the Middle Eocene (Lutetian) and to Subzone CP12b which was studied by Okada and Bukry (1981) aged of the Middle Eocene (Lutetian) this biozone corresponds to biozne CNE 8 which was studied by Agnini et al. (2014) aged of the Middle Eocene (Lutetian) therefore, the middle Eocene was suggested in this study. (Gradstein et al., 2012) (Diags. 1-3). 4 – Nannotetrina alata Interval biozone (CNE 9) Definition: Interval biozone of Nannotetrina alata. Boundaries: The biozone is determined by the first occurrence of Nannotetrina alata to the first occurrence of Chiasmolithus gigas. Thickness: Between (1225-1220) m. depths. 351 Al-Nuaimi and Al-Badrani Correlation and Discussion: This biozone is correlated to the lower biozone of NP15which was studied by Martini (1971) aged of the Middle Eocene (Lutetian) and to Subzone CP5 which was studied by Okada and Bukry (1981) aged of the Middle Eocene (Lutetian). This biozone corresponds to biozne CNE 9 which was studied by Agnini et al. (2014) aged of the Middle Eocene (Lutetian) therefore, the middle Eocene was suggested in this study (Gradstein et al., 2012) (Diags.1-3). 5 – Chiasmolithus gigas Range Biozone (CNE 10-11) Definition: Range biozone of Chiasmolithus gigas. Boundaries: The biozone determinate by the first occurrence of Chiasmolithus gigas to the last occurrence of Chiasmolithus gigas. Thickness: Between (1220-1195) m. depths. Correlation and Discussion: This biozone is correlated to the middle biozoneof NP15 which was studied by Martini (1971) aged of the Middle Eocene (Lutetian) and Subzone CP13b, which was studied by Okada and Bukry (1981) aged of the Middle Eocene (Lutetian). This biozone corresponds to biozones CNE 9 and 10 which was studied by Agnini et al. (2014) aged of the Middle Eocene (Lutetian) therefore, the middle Eocene was suggested in this study as well. (Gradstein et al., 2012) (Diags. 1-3). CONCLUSIONS The Jaddala Formation in (Aj-10) well has five biostratigraphic zones, which include the following: Reticulofenestra dictyoda Partial Range Biozone (CNE 5); Discoaster sublodoensis Interval biozone (CNE 6-7); Nannotetrina cristata Interval biozone (CNE 8); Nannotetrina alata Interval biozone (CNE 9) and Chiasmolithus gigas Range Biozone (CNE 10-11). These Biozones are correlated with other calcareous nannofossils biozones from both local and regional sections leading to conclude that the age of the studied section is Early to Middle Eocene (Yprsian toLutetian). 352 Calcareous nannofossils biostratigraphy of Jaddala Diagram (2): Range chart of calcareous nannofossils throughout studied section. 353 Al-Nuaimi and Al-Badrani Diagram (3): correlated chart of calcareous nannofossils biozones for studied section 354 Calcareous nannofossils biostratigraphy of Jaddala ACKNOWLEDGMENTS We would like to thank Mosul University, College of Science, Geology Department for supporting the authors by offering laboratory to accomplish this work. LITEREATURE CITED Al-Badrani, O. A. 2007.The study of calcareous nannofossils of Middle Eocene – Lower Miocene successions in Sinjar Anticline section, Northwest Iraq. Unpublished Ph.D. Thesis, College of Science, University of Mosul, 119 pp (In Arabic). Al-Badrani, O. A. 2011. 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( Aj-10الطباقية الحياتية لمتحجرات النانو الكلسية لتكوين جدالة في بئر) وسط العراق *عمر احمد البدراني و *اسراء صباح النعيمي قسم علوم االرض، كلية العلوم، جامعة الموصل، الموصل، العراق. * 20/6/2021 ، تأريخ النشر: 24/05/2021، تأريخ القبول: 11/02/2021تأريخ االستالم: الخالصة اجريت دراسة تفصيلية لمتحجرات النانو الكلسية لتكوين جدالة في بئر (Aj-10 ،متحجرات اجناس من نوع وسبعون واحد شخص العراق. وسط ) لها تم االمتدادات الطباقية وباالعتماد على مفتوح التسمية، منها ترك البعض ة هي: تحديد خمسة انطقة حياتية لتكوين جدال (1)Reticulofenestra dictyoda Partial Range Biozone (CNE 5), (2)Discoaster sublodoensis Interval biozone (CNE 6-7), (3)Nannotetrina cristata Interval biozone (CNE 8), (4)Nannotetrina alata Interval biozone (CNE 9), (5)Chiasmolithus gigas Range Biozone (CNE 10- 11). عمر التكوين في قورنت بمثيالتها قادت الى تحيد هذه االنطقة الحياتية هذا المقطع بااليوسين االوسط )اليبرسييان الى اللوتيشيان(. Calcareous nannofossils biostratigraphy of Jaddala