Facies of Miocene deposits in south of Harsin, High Zagros

Document Type : Original Article

Authors

1 Department of Geology, Faculty of Science, Lorestan University, Khoramabad, Iran

2 Department of Geology, Faculty of Science, Isfahan University, Isfehan, Iran

Abstract

Introduction
Lower Miocene deposits in Iran have a significant expansion. In Zagros and Central Iran, these sediments include Asmari and Qom formations, respectively. Due to its economic importance and especially the possibility of reservoir and cap rocks, many studies have been conducted on the Miocene deposits in areas with high hydrocarbon potential. However, in the high Zagros, due to the limited oil reserves, the Miocene deposits have been less studied. According to the geological map of Harsin in the northern parts of the high Zagros zone (Shahidi and Nazari, 1997), the Miocene deposits consist of carbonate and clastic rocks. In terms of lithology, especially the presence of clastic rocks, these deposits are very similar to the Qom Formation, but since they are located in the high Zagros zone, it may not be correct to refer to this formation. On the other hand, the lithology and appearance of these deposits are fundamentally different from the Asmari Formation. Therefore, in this paper, like the geological map of Harsin, they are called Miocene deposits. In this paper, the paleoenvironment and microfacies of Miocene deposits in the high Zagros have been studied.
Material and methods
Three sections of Miocene deposits are studied, located 23 km south of Harsin (Figure 1).
 
 
Fig. 1. Locality map of the studied area.
 
In the present study, a total of 130 sections were taken. Thin sections were prepared from rock samples and isolated fossils were isolated from soft samples. Texture properties and fossil assemblages in thin sections were examined and identified by a polarizing microscope.
Biostratigraphy
Based on foraminiferal distribution, the following assemblage zones are recognized:
1) Indeterminate Zone I: In view of the fact that we unable to find any index microfossils, comments on the age of this zone are difficult, which explains why this is here referred to as an indeterminate zone.
2) SBZ25: Larger benthic foraminiferal zone SBZ 25 can be divided into two subzones; those of M. globulina and M. intermedia.
2-a) M. globulina Subzone: This is defined by the FO of M. globulina at the base and the FO of M. intermedia at the top. It is regarded as a common global index for the Burdigalian Stage.
2-b) M. intermedia Subzone: This is defined by the stratigraphical range of M. intermedia, which is considered to be a characteristic form for the middle-upper Burdigalian (Cahuzac & Poignant, 1997).
 1) Indeterminate Zone II: In view of the fact that we could not find any index microfossils in this zone, we here refer to it as indeterminate zone. As to its stratigraphical position, we prefer an early Langhian date for this zone.
2) Orbulina suturalis Interval Zone: Planktonic foraminifera are frequent to dominant in the upper part of the Sayl Cheshmeh section. Based on their vertical distribution, a single biozone has been recognized. This is defined by the FO of O. suturalis (Brönnimann, 1951) and ends right below the conglomerate/sandstone levels of Pliocene age
Depositional model
Based on the field observations, petrographic studies and textural characteristics as well as the abundance and distribution of foraminiferal fauna and other components, 7 carbonate microfacies have been identified. These carbonate microfacies were deposited in4 facies belts including lagoon, margin facies, upper slope facies and lower slope facies (Fig. 2).
 
 
Fig. 2. Depositional model for the platform carbonate of the Miocene deposits in the Harsin area, High Zagros Zone
 
The stratigraphical position and vertical and lateral dispersion of different facies along with textural features and skeletal composition, and the presence of coral reef reefs and sudden change of facies and the absence of large tidal zones of Miocene deposars in Harsin area indicate that this sequence deposited on a rimmed carbonate platform.

Keywords

Main Subjects

References

Persian References:
-Danishian, J., Derakhshani, M. and Moalemi, A., 2015 Determination of relative age of deposits of Mishan formation based on Phraminifera and strontium isotope in northwest and west of Bandar Abbas, south of Iran, Stratigraphic and Sedimentological Researches, v. 63(32), v. 54-35.
-Shahidi, M. and Nazari, H., 1997. Geological map of Harsin, 1/100.000 scale: Geological survey of Iran.
 
English References:
-Abbasi, G., Motamedi, H., Orang, K. and Nickandish, A.A., 2020. Petroleum geology of the western part of the Central Iran Basin, Journal of Petroleum Geology, v. 43, p. 171-190.
-Adams, T.D. and Bourgeois, F., 1967. Asmari biostratigraphy. Geological and Exploration Division, Iranian Oil Offshore Company Report number, 1074, (Unpublished).
-Bahamonde, J.R., 2007. Marine red staining of a Pennsylvanian carbonate slope: Environmental oceanographic significance, Journal of Sedimentary Research, v. 77, p. 1026-1045.
-Boudagher-Fadel, M.K. and Price, D., 2010. Evolution and paleogeographic distribution of the lepidocyclinids, Journal of Foraminifera Research, v. 40, p. 79-108.
-Brandano, M., Cornacchia, I., Raffi, I. and Tomasseti, L., 2016. The Oligocene–Miocene stratigraphic evolution of the Majella carbonate platform (Central Apennines, Italy): Sedimentary Geology, v. 333, p. 1-14.
-Brandano, M., Frezza, V., Tomassetti, L., Pedley, M. and Matteucci, R., 2009. Facies analysis and palaeoenvironmental interpretation of the Late Oligocene Attard Member (Lower Coralline Limestone Formation), Malta: Sedimentology, v. 56, p. 1138-1158.
-Cahuzac, B. and Poignant, A., 1997. Essai de biozonation de l’Oligo- Miocène dans les bassins européens à l’aide des grands foraminifères néritiques, The Bulletin de la Société Géologique de France, v. 168, p. 155-169.
-Cosovic, V., Drobne, K. and Moro, A., 2004. Paleoenvironmental model for Eocene foraminiferal limestones of the Adriatic carbonate platform (Istrian Peninsula): Facies, v. 50(1), p. 61-75.
-Daneshian, J. and Ghanbari, M., 2017. Stratigraphic distribution of planktonic foraminifera from the Qom Formation: A case study from the Zanjan area (NW Central Iran), Neues Jahrbuch für Geologie und Paläontologie, v. 283, p. 239-254.
-Daneshian, J. and Ramezani Dana, L., 2019. Benthic foraminiferal events of the Qom Formation in the north Central Iran Zone, Paleontological Research, v. 23, p. 10-23.
-Dill, M.A., Seyrafian, A. and Vaziri-Moghaddam, H., 2012. Palaeoecology of the Oligocene-Miocene Asmari Formation in the Dill Anticline (Zagros Basin, Iran). Neues Jahrbuch fondlungen, v. 263, p. 167-184.
-Dunham, R.J., 1962. Classi Wcation of carbonate rocks according to their depositional texture. In: Ham, W.E. (Ed.), ClassiWcation of Carbonate Rocks: A Symposium: AAPG Bulletin, p. 108-121.
-Embry, A.F. and Klovan, J.E., 1971. A Late Devonian reef tract on northeastern Banks Island, Northwest Territories: Bulletin of Canadian Petroleum Geology, v. 33, p. 730-781.
-Flügel, E., 2010. Microfacies of Carbonate Rocks, Analysis, Interpretation and Application, 2nd edition. Springer - Heidelberg, 976 p.
-Geel, T., 2000. Recognition of stratigraphic sequence in carbonate platform and slope deposits: empirical models based on microfacies analyses of palaeogene deposits in southeastern Spain, Palaeogeography Palaeoclimatology Palaeoecology, v. 155, p. 211-238.
-Halasovas, E., Gürbüz, K. and Cosentino, D., 2013. Middle-Upper Miocene paleogeography of southern Turkey: insights from stratigraphy and calcareous nannofossil biochronology of the Olukpınar and Başyayla sections (Mut-Ermenek Basin). Turkish Journal of Earth Sciences, v. 22, p. 820-838.
-Hottinger, L.W., 1960. Recherches sur les Alvéolines du Paléocène et de l'Éocène Mémoires Suisses de Paléontologie, Basel, 243 p.
-Jones, R.W., Simmons, M.D. and Whittaker, J.E., 2006. On the stratigraphical and paleobiogeographical significance of Borelis melo melo (Fichtel and Moll, 1978) and B. melo curdica (Reichel, 1937) (Foraminifera, Miliolida, Alveolinidae), Journal of Micropaleontology, v. 25, p. 175-185.
-Kenter, J.A.M., Harris, P.M. and Della Porta, G., 2005. Steep microbial boundstone dominated platform margins examples implications, Sedimentary Geology, v. 178, p. 5- 30.
-Marangon, A., Gattolin, G., Della Porta, G. and Preto, N., 2011. The Latemar: A flat-topped, steep fronted platform dominated by microbialites and synsedimentary cements, Sedimentary Geology, v. 240, p. 97-114.
-Mohammadi, E., Vaziri, M.R. and Dastanpour, M., 2013. Biostratigraphy of the nummulitids and epidocyclinids bearing Qom Formation based on larger benthic foraminifera (Sanandaj–Sirjan fore-arc basin and Central Iran back-arc basin, Iran): Arabian Geosciences, v. 13, p. 1136-1146.
-Özcan, E. and Less, G.Y., 2009. First record of the co-occurrence of Western Tethyan and Indo-Pacific larger foraminifera in the Burdigalian of the Mediterranean province, Journal of Foraminiferal Research, v. 39, p. 23-39.
-Pomar, L.B., 2001. Ecological control of sedimentary accommodation: evolution from carbonate palaeobathymetry of corals and coralline algae in Cenozoic reef, In: (eds.) D.W.J. Bosence, and P.A. Allison, Marine Paleoenvironmental Analysis from Fossils, Geological Society, London, v. 83, p. 181-229.
-Rabbani, J., Mirzaie Ataabadi, M. and Shaahsavari, E., 2020. Microfacies, sedimentary environmental model and relative sea level change of marly strata of the Qom Formation in Zarrin-Abad section, South of Zanjan, Journal of Stratigraphy and Sedimentology Researches University of Isfahan, v. 36, p. 115-134.
-Rosen, B.R., Aillud, G.S., Bosellini, F.R., Clack, N.J., Insalaco, E., Valldeperas, F.X. and Wilson, M.E.J., 2002. Platy coral assemblages: 200 million years of functional stability in response to the limiting effects of light and turbidity: Proceedings 9th International Coral Reef Symposium, Bali, Indonesia, p. 23-27.
-Shahidi, M. and Nazari, H., 1997. Geological map of Harsin, 1/100.000 scale: Geological survey of Iran.
-Staffords-Smith, M.G., 1993. Sediment-rejection efficiency of 22 species of Australian scleractinian corals: Marine Biology, v. 115, p. 229-243.
-Strasser, A. and Strohmenger, C., 1997.Early diagenesis in Pleistocene coral reefs, southern Sinai, Egypt: response to tectonics, sealevel and climate, Sedimentology, v. 44, p. 537-558.
-Van Buchem, F.S.P., Allan, T.L., Laursen, G.V., Lotfpour, M., Moallemi, A., Monibi, S., Motiei, H., Pickard, N.A.H., Tahmasbi, A.R., Vedrenne, V. and Vincent, B., 2010. Regional stratigraphic architecture and reservoir types of the Oligo-Miocene deposits in the Dezful Embayment (Asmari and Pabdeh ormations) SW Iran. Geological Society, London, Special Publications, v. 329(1), p. 219-263.
-Vaziri-Moghaddam, H., Seyrafian, A. and Taheri, A., 2010. Oligocene-Miocene ramp system (Asmari Formation) in the NW of the Zagros basin, Iran: microfacies, paleoenvironment and depositional sequence, Revista Mexicana de Ciencias Geológicas, v. 27, p. 56-71.
-Walton, W.R. and Sloan, B.J., 1990. The genus Ammonia Brünnich, 1772: its geographic distribution and morphologic variability:  Journal of foraminifera research, v. 20(2), p. 128-156.
-Wynd, J., 1965. Biofacies of Iranian oil consortium agreement area, Iranian Oil Offshore Company, Report 1082 (Unpublished).
-Wray, J.L., 1977. Calcareous algae: Esevier Publication, Amsterdam, 185 p.
 

Files

Share

How to cite

Statistics