Facies analysis and depositional environment of Gir Bir Formation, Northwestern Iraq

Mohammed A. Al-Hajj , Ali I. Al-Juboury& Aboosh H. Al-Hadidy
Geology Department, Mosul University, Iraq
North Oil Company, Kirkuk, Iraq


Upper Cretaceous successions of the Gir Bir Formation (Cenomanian-Early Turonian)
were studied in 15 wells from northwestern Iraq. The formation is composed of
recrystallized, partly dolomitized limestone with local silicification. Benthonic
foraminifera (Miliolids, Alveolina, and Orbitolina), rudist and peloids are the main
constituents. The studied succession has been affected by several diagenetic events such
as; dolomitization, recrystallization, micritization, dissolution, compaction and
silicification. Facies analysis revealed that seven microfacies subdivided into eleven
submicrofacies could be distinguished, reflecting sedimentary environments including;
deep shelf margin, slope/shoal, rudist buildups, back reef/shoal, and protected lagoon in
a regressive shallowing-upward sequence. Lateral facies variation showed that reefal
facies were commonly located in northwestern parts of the study area, whereas lagoonal
facies existed in eastern and southeastern parts. Rimmed carbonate platform is the
acceptable model for the Gir Bir Formation.

Key Words:
Gir Bir Formation,
Facies, rudist
buildups, rimmed


[1] Murris, R.J. "Middle East stratigraphic evolution and oil habitat". AAPG Bull., 64, pp.597-618. (1980).

[2] Al-Sakini, J.A. "Summary of the petroleum geology of Iraq and the Middle East". Northern Oil
Company Press (Naft –Al-Shamal co.), Kikuk, Iraq (in Arabic), pp. 179. (1992).

[3] Saddoni, F.N. & Aqrawi, A.A.M. "Cretaceous sequence stratigraphy and petroleum potential of the
Mesopotamian basin, Iraq". In: Alsharahn A. & Scott, B. (Eds.) "Middle East Model of Jurassic-Cretaceous
carbonate system", SEPM special publication, 69, pp. 315-334. (2000).

[4] Sharland, P.R., Archer, R., Casey, D.M., Davies, R.B., Hall. S.H., Heward, A.B., Horbury, A.D., &
Simmons, M.D. "Arabian Plate Sequence Stratigraphy", GeoArabia, Special Publication 2, Gulf Petrolink.
Manama, Bahrain, pp.371. (2001).

[5] Aqrawi, A.A.M., Goff, J.C., Horbury, A.D. & Sadooni, F.N. "The Petroleum Geology of Iraq". Scientific
Press, pp. 424. (2010).

[6] Beydoun, Z.R. "Arabian hydrocarbon geology and potential, plate tectonic approach". AAPG studies in
Geology, 19-29. (1991).

[7] Buday, T. "The Regional Geology of Iraq, Stratigraphy and Paleogeography". Dar Al-Kutub publishing
house, Mosul University. Mosul, Iraq, pp. 445. (1980).

[8] Jassim, S.Z. and Goff, J.C. "Geology of Iraq". Dolin, Prague and Moravian Museum, Brno, Czech
Republic. Pp.341. (2006).

[9] Chatton, M. & Hart, E. " Review of the Cenomanian to Maestrichtian stratigraphy in Iraq". Unpublished
report, Iraq Petroleum Company, Palaeontological Department, Kirkuk.(1961).

[10] Schlager, W. & Philip, J. "Cretaceous Carbonate platforms", In: Gisburg, R.N. & Beaud, B. (Eds.)
"Cretaceous Resources, Events and Rhythms". NATO ASC series 304, Kluwer Academic Publisher, pp.173-
195. (1990).

[11] Jassim, S.Z. and Buday, T. "Late Tithonian-Early Turonian Megasequence AP8": In Jassim, S.Z. and
Goff, J.C. (eds) "Geology of Iraq". Published by Dolin, Prague and Moravian Museum, Brno. pp. 124-154.

[12] Bellen, V.R.G., Dunnington, H.V., Wetzel, R. and Morton, D.M. "Lexique Stratigraphic
International". V.3, Asie Fascicule loa-Iraq. Paris, pp. 333. (1959).

[13] Al-Jawari, H.A.KH. "Study of Upper Cretaceous at selected sections of Sfia wells NW Iraq", MSc
thesis, Baghdad University, Iraq. (1989).

[14] Al-Esa, M.E. & Fassola, N.A. "Biostratigraphy of the Upper Cretaceous reservoir at Butmah field". Oil
studies and Researches Journal, 2, 152-168. (2011).

[15] Gradstein, F.M., Ogg, J.G., Smith, A.G., Bleeker, W. & Lourens, L.J."A new geologic time scale 2004".
Cambridge University Press, pp.589.(2004).

[16] Al-Naqib, K.M. "Geology of the Arabian Peninsula, southern west Iraq". United States Geological
survey, Professional Paper, No. 560-G, pp. 54. (1967).

[17] Wilson, J.L. "Carbonate Facies in Geological History". Springer-Verlag New York Heidelberg Berlin,
pp. 471. (1975).

[18] Flügel, E." Microfacies of Limestone", Christenson, K. (Translator), Springer-Verlag, Berlin, pp.633.

[19] Flügel E. "Microfacies of Carbonate Rock, Analysis, Interpretation and Application". Springer-Verlag,
Berlin, pp. 976. (2004).

[20] Boudagher, M.K. "Evolution and Geological Significance of Larger Benthic Foraminifera".
Developments in Paleontology and Stratigraphy, 21, Elsevier, pp. 540. (2008).

[21] Mack, G. H., James, W. C. "Cyclic sedimentation in the mixed siliciclastic- carbonate Abo-Hueco
transitional zone (Lower Permian), southwestern New Mexico". Journal Sedimentary Petrology 56, pp. 635-
647. (1986).

[22] James, N.P. "Reef and mound": In Walker, R.G. and James, N.P.,(eds.) "Facies Models, Response to
Sea Level Change". Geo.Text1, Geol. Asso. of Canada, pp.27-47. (1979).

[23] Gibson, T.G. "Planktonic benthonic foraminiferal ratios: Modren Patterns and Tertiary applicability".
Marine Micropalentology, V.15, pp.29-52. (1989).

[24] Lehrman, D.J., Wei, J. and Enos. P. "Controls on facies architecture of a large Triassic carbonate
platform, the great bank of Guizhou, Nanpanjiang basin, south China". Jour. sed. Res., V.68, No.2, pp.311-

[25] Chillingar, G.V., Bissell, H.J. and Faibridge, R.W."Carbonate Rocks: Origin, Occurrence,
Classification". Elsevier Published Company Amserdam, pp.471 (1967).

[26] Adams, T.D., Khlili, M. and Khorsrovi Said, A. "Stratigraphic significance of some oligosteginid
assemblages from Lurestan province northwest Iran". Micropalaeontology , No.13, P.55-67. (1967).

[27] Pomar, L., Gilil, E., Obrador, A., and Ward, W. "Facies architecture and high-resolution sequence
stratigraphy of Upper Cretaceous platoform margin succession, southern central Pyrenees. Spain".
Sedimentary Geology, V.175, pp.339-365. (2005).

[28] Laviano, A., Maresca, M. and Tropeano, M. "Stratigraphic organization of rudist biogenic beds in the
Upper Cenomanian successions of the Western Murge (Apulia, Southern Italy)".GEOBIOS, V.22, pp.159-

[29] Carannante, G., Graziano, R., Pappone, G., Ruberti, D., and Simone, L. "Deposition system and
response to sea level oscillations of the Sennonia rudist bearing carbonate shelves, Examples from central
Mediterranean areas". Facies, V.40, pp.1-124. (1999).

[30] Simmons, M.D., Whittaker, J.E. and Jones, R.W. "Orbitolinids from Cretaceous sediments of the
Middle East-a revision of the F.R.S. Henson. and associates collection": In Hart, M.B., Kaminski, M. and
Smart, C.,(Eds). Proceeding of the 5th International workshop on Agglutinating Foraminiferal . Grzybowsiki
Foundation, special publication, 7, pp.411-437. (2000).

[31] Coogan, A. H. "Early and Middle Cretaceous Hippuritacea (rudist) of the Gulf Coast": In Bebout, D.
G., and Loucks, R.G., (eds) "Cretaceous carbonate of Texas and Mexico". Bur. of Econ. Geol., University of
Texas, report of investigation No.89, pp.32-70. (1977).

[32] Wood, R. "The changing biology of reef-building". Palaios, V.10, pp.517-529. (1995).

[33] Riding, R. "Structure and composition of organic reefs and carbonate mud mounds: Concepts and
categories". Earth-Science Reviews, V.58, pp.163-231. (2002).

[34] James, N.P. "Reef environment": In Scholle, P.A., Bobout, D.G. and Moor, C.H.,(eds.) "Carbonate
Depositional Environments". AAPG, Bull., Memoir 33, pp.345-440. (1983).

[35] Wood, R. "Nutrients, predation and the history of reef building". Palaios, V.8, pp.526-543. (1993).

[36] Antoshkina, A. "Organic buildups and reefs on the Paleozoic carbonate platform margin", Pechor-
Urale, Russia. Sedimentary Geology, V.118, pp..187-211. (1998).

[37] Forman, M.J. and Schlanger, S.O. "Tertiary reef and associated limestone facies from Lourisiana and
Guma." Geology. V.65, pp. 611-627. (1957).

[38] Murray, J.W. "Ecology and Applications of Benthic Foraminifera". Cambridge University Press,
Cambridge, pp.426. (2004).

[39] Platel, J.P. "The Turonian rudist-bearing carbonate platforms of the Charentes et du Peŕigord areas,
Aquitaine basin(France)". Gēogios, M.S,.No.22, pp.295-311. (1998).

[40] Schafer, P. and Senowbari-Daryan, B. "Facies development and palaeoecologic zonation of four Upper
Triassic patch-reefs, Northern calcareous Alps near Salzburg, Austria": In Tommey, D.F.(eds.) "European
Fossils Reef Models". SEPM, Special Publication, No.30, pp.241-260. (1981).

[41] Longman, M.W. "A process approach to recognizing facies of reef complexes": In Toomey, D.F.,(eds.)
"European Fossils Reef Models". SEPM, special publication, No.30, pp. 9-40. (1981).

[42] Hedley, R. H. and Adams, G.G. "Foraminifera". Academic press, London, pp.265. (1976).

[43] Hallock, P. and Clenn, E.C. "Larger foraminifera: A tool for paleoenvrionmental analysis of Cenozoic
carbonate depositional facies". Palaios, V.1, pp.55-64. (1986).

[44] Polsak, A. "Upper Cretaceous biolithic complexes in a subduction zone: Examples from the Inner
Dinarides, Yugoslavia": In Toomey, D.F., (eds.) "European Fossil Reef Models". SEPM., Special Publication, No.30, 
, pp.447-473.(1981).

[45] Burchette, T.P. & Britton, S.R. "Carbonate facies analysis in the exploration for hydrocarbons : a case-
study from the Cretaceous of the Middle East". In: Brenchley, P.J. & Williams, B.P. (Eds), Sedimentology,
Recent Development and Applied Aspect. Blackwell, 185-199. (1985).

[46] Read, J.F. "Carbonate platform facies models". AAPG. Bull, .1,P.1-21. (1985).

[47] Eberli, G.P., Ginsburg, R.N. "Segmentation and coalescene of Cenozoic carbonate platforms,
Northwest Great Bahama Cobequid Bay-Salmon River Estuary (Bay of Fundy)". Sedimentology. V.37,

[48] Philip, J., Borgomano, J. and Al-Makiry, S. "Cenomanian-Early Turonian carbonate platform of
Northern Oman: Stratigraphy and palaeo-environments". Palaeogeography, Palaeoclimatology,
Palaeoecology, V. 119, pp.77-92. (1995).

[49] Steuber, T., and Loser, H. "Species richness and abundance patterns of Tethyan Cretaceous rudist
bivalves (Mollusca: Hippuritacea) in the central-eastral Mediterranean and Middle East, analyzed from a
palaeontological database". Palaeogeography, Paleoclimatology, Palaeoecology, V.162, pp.75-104. (2000).

[50] Ferry, S., Merran, Y., Grosheny, D. and Mrouech, M. "The Cretaceous of Lebanon in the Middle East
(Levant) context". Notebooks on Geology, 2, pp. 38-42.(2007).

[51] Sherwani, G.H. "Sequence stratigraphy and sedimentary systems of Cenomenian-Early Turonian in
southern Iraq". Unpublished Ph.D. Thesis, University of Baghdad. Iraq, pp. 147. (1998).

[52] Metwali, M.H., Philip, G. and Moussly, M.M. "Petroleum bearing formations in Norheastern Syria and
Northern Iraq". AAPG. Bull.,V.58, No.9, pp.1781-1796. (1974).

[53] Al-Mashadani, A. "Geodynamic evolution of Iraqi sedimentary bsins: Consequences of the distribution
of fluids." DSc. Thesis, Pau University, France, pp. 320. (1984).

[54] Sadooni, F.N. "The nature and origin of Upper Cretaceous basin-margin rudist buildups of the
Mesopotamian Basin, southern Iraq, with consideration of possible hydrocarbon stratigraphy entrapment".
Cretaceous Research, V. 26, pp.213-224. (2005).

[55] Ameen, M.S. "Effect of basement tectonics on hydrocarbon generation, migration and accumulation in
Northern Iraq". AAPG. Bull, V.76, No.3, pp.356-370. (1992).