Document Type : Research Paper

Authors

1 Department of Geology, Collage of Science, University of Anbar, Anbar, Iraq;

2 Department of Geology, Collage of Science, University of Anbar, Anbar, Iraq

Abstract

The Upper Oligocene – Middle Miocene succession in Wadi Heglan, western Iraq was carried out to study microfacies and paleoenvironment.  The Anah and Euphrates formations are exposed in this section. Anah Formation consists of massive, coralline, and dolomitic limestone, while the Euphrates Formation consists of massive and become well bedded upwards, obvious porous, marly, and dolomitic limestone. The abundance of benthic foraminifera and other fossils within these facies, the appropriate paleoenvironment for the Anah and Euphrates formations were determined. The reef and back-reef environments are recognized Anah Formation and the restricted to open marine environments are recognized Euphrates Formation. The Anah Formation exposed in this section by long episode of high stand trace (HST) which represent fall sea level of back-reef facies, while Euphrates Formation was deposited during three fourth-order cycles (A, B, and C), these cycles represent a succession episode of sea level rises (TST) and stillstands (HST). These sequences are bounded by two type-1 sequence boundary SB1. The area of study show very low rate of subsidence according to sequence development and the main factors that affect the study area is the fluctuation of eustatic sea level..

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[1] Al-Dabbas  M. A., Awadh, S. M. , and Zaid, A. A., 2014. Facies analysis and   geochemistry of the  Euphrates Formation in Central Iraq.  Arabian Journal of   Geosciences,7: 1799-1810.
[2] Al-Ghreri, M.F.,2015. Benthic Foraminifera biostratigraphy of the Euphrates Formation  (Early Lower Miocene – Middle Miocene) in selected sections, Western Iraq. Iraqi Journal of Science .56(1B):424-434.
[3] Al-Qayim, B., Ibrahim, A., and Kharajiany, S., 2016. Microfacis and sequence   stratigraphy of the Oligocene–Miocene sequence at Golan Mountian, Kurdistan,   Iraq. Carbonates and Evaporites31, 259-276.
[4] Al-Nuaimy Q. A. M., 2018. Morphometric analysis of chattian- Early Aquitanian                   Miogypsinidae from Iraq and their stratigraphic distribution in the Arabian Tethys . Arabian Journal of Geosciences 10:542, 2-17.
 [5] Alkhaykanee, M. H., and Al-Dulaimi, S. I., 2019. "Biostratigraphy of Euphrates, Dhiban, and Jeribe Formations in Ajil oil field, Salah Al-Deen Governorate,  central Iraq." Iraqi Journal of Science 263-276.
[6] Ameen  F. A. , Fattah  A. I. , and Qader  B. O., 2020. Microfacies and depositional  environment of Upper Oligocene and lower Miocene successions from Iraqi Kurdistan Region . Kuwait  Journal  of Sciences. 47(4).
[7]Abdulrahman A., and Awadh S.M., 2021. Depositional Environment of the Ibrahim              Formation and Determining the Oligocene- Early Miocene Boundary in     Eastern Iraq.   The Iraqi Geological Journal, 85-97.   
[8] Qader F. M., and Ali S. M., 2022. Reservoir Characteristics of the Lower Miocene                     Carbonate Formation in Kor Mor Gasfield, Kirkuk Area, NE Iraq. Tikrit Journal of Pure Science, 27(3): 43-52.
 [9] Turki, F. H., and Awadh, S. M. (2023). Discrimination Reef and Non-Reef Environments, Using REE Geochemistry. The Iraqi Geological Journal, 1-11.
[10] Jassim, S. Z., and Goff, J. C., 2006. Geology of Iraq, 1st. Edited by Lea Novotna. Dolin, Hlavni 2732, Prague and Moravian Museum, Zelny trh 6, Brno, Czech Republic, 362 P.
[11] Fouad, S. F. A., 2007. Tectonic and Structural Evolution of Iraqi. Bulletin of Geology and Mining, Special Issue . Geology of Iraqi Western Desert.                           
[12] Geel, T., 2000. Recognition of  stratigraphic sequences in carbonate platform and                    slope  deposies: empirical models based on microfacies  analysis of  Paleocene deposits in southeastern Spain ,Paleogeography ,Paleoclimatology , Paleoecology 155: 211-223.                                             
[13] Edgell, H. S. (1997). Significance of reef Limestones as oil and gas reservoirs  in the Middle East and North Africa. 4-5 www.google.com.tmsoc.org.
 [14] Flugel ,  E.  2010. Microfacies  of  carbonate rocks : analysis, interpretation and application, 2nd ed.  Springer, Berlin 929 p.
[15] Hassan, S. H. and Ghosh, A. K.,  2003. Early Oligocene non-geniculate coralline algal assemblage from Al-Bayda Formation, Northeast Libya Current Science, , 84(4): 552-587.
 [16] Romero, J. E., and  Rossel , J., 2002. A model for the palaeoenvironmental distribution of larger foraminifera based on Late Middle Eocene deposits on the margin of the South Pyrenean basin. Palaeogeography, Palaeoclimatol ,  Palaeoecol 179 : 43– 56.
[17] Al-Ghreri, M. F., Al-Hetty, S. O., and Al-jibori, A. S., 2016. Facies characteristics, depositional environment and sequences stratigraphy of the Euphrates Formation in Hadetha Area, Western Iraq.'' Al-Nahrain Journal of Science 19(2)69-79. 
[18] Gayara A.D., and Taha L.S., 1989. Microfacies analysis of the Euphrates Limestone Formation. Northern Iraq Jour Geol Soc Iraq 22(1):123–129.
 [19] Bosellini, F. R., Russo, A., & Vescogni, A., 2002. The Messinian reef complex of the Salento Peninsula (southern Italy): stratigraphy, facies and paleoenvironmental interpretation. Facies47, 91-112.
 [20] Bassi, D. , Hottinger ,L. , and Nebelsick , H., 2007. Large Foraminifera from the  Upper Oligocene of the Venetian area, northeast Italy: Paleontology 5 (4) :845-868.
[21] Brandano , M. ,Frezza ,V. ,Tomasstti , L., Cuffaro , M., 2009 . Heterozoan carbonate    in oligotrophic tropical waters: The attard member of the lower coralline   limestone Formation (Upper Oligocene, maltal). Palaeogeography, Palaeoclimatology, Palaeoecology,  272: 1-10.
[22] Ghosh , A. M., 2002. Cenozoic coralline algal assemblage from southwestern kutch and its importance in palaeoenvironment and palaeobathymetry . Current science, Vol . 83 , No.2 ,pp.153-158.
 [23] Flugel , E., 2004. Microfacies of carbonate rocks . Analysis interpretation and application.  Springer, Berlin , 976 p.
 [24] Beavintone , S. J. ,and  Racey , A.,  2004. Ecology of extant nummulitids and other large benthic Foraminifera. Applications in Palaeoenvironmental analysis: Earth Science Review 67 (3-4): 219-265.
 [25] Rasser ,  M. W. ,  Scheibner , C. , and  Mutti , M., 2005. A  paleoenvironmental    standard  section for  lower Ilerdian tropical carbonate factories  (Pyrenees , Spain : +Corbieres . France ) . Facies , 51 : 217-232.