Microbiostratigraphy and paleoecology of the Qom Formation in the Goylar section, southwest of Zanjan Province


Faculty of Science, Department of Geology, Payame Noor University (PNU), Tehran, Iran


A stratigraphic section (155 meter in the thickness) was selected to determine biostratigraphic and paleoecological features of Qom Formation in southwestern Zanjan province, Central Iran geological zone. Field observations show that the Qom Formation is composed of cream to brown, thin-to thick bedded limestone, sandy limestone, alternation of shale and green marl, reef-coral limestone, and green marl and argillitic limestone.According to paleontological studies, a total of 24 genera and 18 species including 17 genera and 9 species of benthic foraminifera and 7 genera and 9 species of planktonic foraminifera have been identified. Based on the stratigraphic distribution of foraminifera, Borelis melocurdica-Borelis melomelo Assemblage Zone (Burdigalian, Early Miocene) has been recognized with certainty for the Qom Formation and 5-meters in the thickness of basal Qom deposits (Lower boundary on volcanic rocks) is considered to be the possible age of Aquitainian (?). Base on paleoecological features including the abundance of fossil assemblages, morpho-types, shell types of benthic and planktonic foraminifera, and the abundance of reef corals along with algal coexistence, the Qom sea has a normal salinity and semi warm to warm in the temperature. Also, light changes in the Qom Sea have been mainly in the Mesophotic-Oligophotic and Aphotic zones. Base on the fauna bathymetry, sedimentation of the Qom Formation has been occurred in a carbonate shelf ? in the lagoon, barrier to the deep open marine depositional setting.


Adams, T.D., Bourgeois, F., 1967. Asmari biostratigraphy Iran, Oil Operation Company, Geological Exploration. Report No. 1074, 1–37.
Aghanabati, A., 2005. Geological of Iran. Geological survey of Iran, 560.
Al-Saad, H., Ibrahim, M., 2002. Stratigheraphy micropaleontology and Palaeoecology of the Miocene Damam Formation Qatar.  Geo Arabia 7(1), 9-28.
Blow, W., H., 1969. Late Middle Eocene to recent planktonic foraminiferal biostratigraphy. In: Bronnimann P, Renz H H, eds. Proceedings of the First International Conference on Planktonic Microfossils. Leiden: E. J. Brill, 199–421.
Boggs, S., 1987. Principles of Sedimentology and Stratigraphy by Sam Boggs. Longman Higher Education.
Bolli, H., M., Saunders, J. B., 1985. Oligocene to Holocene low latitude planktic foraminifera. In: Bolli H M, Saunders J B, Perch-Nielson K, eds. Plankton Stratigraphy. Cambridge University Press, 155–262
Bozorgnia, F., 1966. Qum Formation stratigraphy of the Central Basin of Iran and its intercontinental position. Bull Iran Pet Inst 24, 69–75.
Buxton, M.W.N., Pedley, H.M., 1989. A Standardized Model for Tethyan Tertiary Carbonates Ramps. Journal of the Geological Society 146, 746-748.
Cahuzac, B., Poignant, A., 1997. An attempt of biozonation of the European basin, by means of larger neritic foraminifera. Bulletin de la Société géologique de France 168 (2), 155-169.
Ehrenberg, S.N, Pickard, N.A., Laursen, G.V., Monibi, S., Mossadegh, Z.K., Svånå, T.A., Aqrawi, A.A.M., McArthur, J.M., Thirlwall, M.F., 2007. Strontium isotope stratigraphy of the Asmari Formation (Oligocene-Lower Miocene), SW Iran. Petroleum Geology 30(2), 107–128.
Flugel, E., 2004. Carbonate sedimentary rocks: Berlin, Springer, p. 976.
Furrer, M.A., Soder, P., A., 1955. The Oligo–Miocene marine Formation in the Qom region (Central Iran). In: Proceedings of 4th World Petrology Congress. Roma, section I/A/5, 267–277.
Geel, T., 2000. Recognition of stratigraphic sequences in carbonate platform and slope deposits: empirical models based on microfacies analysis of paleogene deposits in southeastern Spain. Palaeogeography, Palaeoclimatology, Palaeoecology155, 211-238.
Iaccarino, A., Premoli-Silva, M., 2005. Practical Manual of Oligocene to Middle Miocene Planktonic Foraminifera, International School on Planktonic Foraminifera, 4th course, 14e18 February. University of Perugia Press, Perugia.
Keller, G., 1999. The Cretaceous-Tertiary Mass extinction in planktonic foraminifera: Biotic Constrains for Catastrophe theories. New York, London, p. 49-83.
Kennett, J., M., Srinivasan, M., S., 1983. Neogene Planktonic Foraminifera: A Phylogenetic Atlas. Pennsylvania: Hutchinson Ross publishing Company, p. 1–263.
Laursen, G. V., Monibi, S., Allan, T. L., Pickard, N. A., Hosseiney, A., Vincent, B., Hamon, Y., Van Buchem, F. H., Moallemi, A., Driullion, G. 2009. The Asmari Formation revisited: changed stratigraphic allocation and new biozonation. 1st International Petroleum Conference and Exhibition, Shiraz, Iran, p. 4–6.
Loeblich, A., R., Tappan, J., H., 1988. Foraminiferal genera and their classification. Van Nostrand Reinhold Company, p. 1–869.
Murray, J.W., 1973. Distribution and Ecology of Living Benthic Foraminifera.Longman Scientific & Technical, London, p. 397.
Wade, B.S., Pearson, P.N., Berggren, W.A., Pälike, H., 2011. Review and revision of Cenozoic tropical planktonic foraminiferal biostratigraphy and calibration to the geomagnetic polarity and astronomical time scale. Earth Science Review 104 (1-3), 111–142.
Wilson, B., 2005. Planktonic foraminiferal biostratigraphy and paleoecology of the Brasso Formation (Middle Miocene) at St. Fabien Quarry, Trinidad, West Indies. Caribbean Journal of Science 4, 797–803.
Wynd, J., 1965. Biofacies of the Iranian consortium agreement area.Iranian Oil Offshore Company Report No. 1082.