Biostratigraphy and paleoecology of the Asmari Formation at northwest of Deris Village, west of Fars Province

Document Type : مقالات پژوهشی

Authors

• Samir Akhzari
• Ali Seyrafian
• Hossein Vaziri-Moghaddam

University of Isfahan

10.22067/sed.facies.v10i2.55860

Abstract

Introduction
The Asmari Formation at Deris section has been studied in order to biostratigraphy and paleoecology observations. This section with the thickness of 460 m is located at northwest of Deris village, in interior Fars zone of the Zagros Basin with coordinates of E: 51° 32' 26'', N: 29° 41' 59''. The Asmari Formation deposits in this section consists of interbedded gray and cream to gray thin, medium, thick and massive limestone, with slightly dolomitic nodular and marl. Based on field studies and according to the thickness of the layers, color and lithology, 5 lithostratigraphic units have been nominated for the mentioned section.
Method and Materials
Using regional geological maps, the study section was identified and measured. Field observation focused on detailed description of bed-by-bed thickness, color, lithology and biotic components systematically. 450 samples from the Asmari Formation were collected. Field works were completed with the study of more than 270 thin-sections for identification of skeletal debris, fabric characteristics and microfacies interpretation. Biostratigraphy results have been determined and concluded based on Ehrenberg et al., (2007) and recent biozones introduced by Laursen et al., (2009) and van Buchem et al., (2010).
Result and Discussion
Biostratigraphy study based on the distribution of benthic foraminifera, led to identification of 19 genera and 19 species, accordingly two assemblage zones have been recognized and Oligocene (Rupelian-Chattian) age was introduced for the Asmari Formation in the Deris section. The suggested assemblage zones are:
1- Nummulites vascus - Nummulites fichteli Assemblage Zone (Rupelian)
This collection has been deployed from the base of the section to the thickness of 66 m and consists of Nummulites vascus, Nummulites fichteli, Nummulites sp., Operculina sp., Amphistegina sp., Heterostegina sp., Elphidium sp.1, Elphidium sp.14, Dendritina rangi, Planorbulina sp., Neorotalia viennoti, Haplophragmium slingeri, Nephrolepidina tournoueri, Nephrolepidina sp., Sphaerogypsina sp., Eulepidina sp., Subterranophyllum thomasi, corralinacean algae, miliolids and textularids.
Based on strontium isotope study by Ehrenberg et al. (2007), because of the presence of Nummulites spp. this assemblage indicates the Rupelian stage. On the other part, it is equivalent to the assemblage zone number two of Laursen et al., (2009) (Nummulites vascus - Nummulites fichteli Assemblage Zone) and van Buchem et al., (2010). The age is Rupelian stage.
2- Archaias asmaricus - Archaias hensoni - Miogypsinoides complanatus Assemblage Zone (Chattian)
This association is introduced for the thickness of 66-460 m and consists of Operculina sp., Amphistegina sp., Heterostegina sp., Elphidium sp.1, Elphidium sp.14, Dendritina rangi, Planorbulina sp., Neorotalia viennoti, Haplophragmium slingeri, Sphaerogypsina sp., Eulepidina sp., Nephrolepidina tournoueri, Nephrolepidina sp., Reussella sp., Valvulinid sp., Borelis cf. pygmaea, Triloculina trigonula, Triloculina cf. tricarinata, Pyrgo sp., Archaias asmaricus, Archaias operculiniformis, Archaias sp., Peneroplis thomasi, Peneroplis evolutus, Peneroplis sp., Austrotrillina howchini, Austrotrillina sp., Meandropsina iranica, Discorbis sp., Ditrupa sp., Spirolina sp., Spiroloculina sp., Bigenerina sp., Miogypsinoides cf. complanatus, Subterranophyllum thomasi, corralinacean algae, miliolids and textularids.
It is equivalent to the assemblage number four of Laursen et al., (2009) (Archaias asmaricus - Archaias hensoni - Miogypsinoides complanatus Assemblage Zone) and van Buchem et al., (2010). So, it is considered as Chattian in age.
In this study, the Asmari Formation biozones of Deris section also have been correlated with two other sections in the Internal Fars zone and Dezful Embayment zone of Zagros Basin. This comparison confirms that the foreland basin of Zagros becomes deeper in SE to NW protraction.
Some ecological factors such as sedimentary basin substrate, depth and hydrostatic pressure, water energy, temperature, turbidity and light influence the distribution and frequency of organisms specially benthic foraminifera (Hottinger, 1983; Romero et al., 2002; Bassi et al., 2007; Flugel, 2010). By study of skeletal elements and accumulation of carbonate grains, it was found that the Oligocene Asmari Formation carbonates have been deposited in the waters of the tropics. Moreover, detailed analysis of microfacies and paleoecology shows that the association of skeletal debris is heterozoan (foralgal, rodalgal and foramol) in this section.
 Key word: Zagros Basin, Interior Fars, Asmari Formation, Oligocene, biostratigraphy, paleoecology
 References
Bassi, D., Hottinger, L., & Nebelsick, J.H., 2007. Larger foraminifera from the Upper Oligocene of the Venetian area, North-East Italy. Paleontology, 50 (4): 845-868.                                           
Ehrenberg, S.N., Pickard, N.A.H., Laursen, G.V., Monibi, S., Mossadegh, Z.K., Svana, T.A., Agrawi, A.A.M., Mc Arthur, J.M., & Thirlwall, M.F., 2007. Strontium isotope stratigraphy of the Asmari Formation (Oligocene – Lower Miocene), SW Iran. Journal of Petroleum Geology, 30: 107-128.
Flugel, E., 2010. Microfacies of Carbonate Rocks: Springer, 984 p.                                                      
Hottinger, L., 1983. Processes determining the distribution of larger foraminifera in space and time. Utrecht Micropaleontological Bulletins, 30: 239-253.                                                                   
Laursen, G.V, Monibi, S., Allan, T.L., Pickard, N.A.H., Hosseiney, A., Vincent, B., Hamon, Y., Van Buchem, F.S.H., Moallemi, A., & Driullion, G., 2009. The Asmari Formation revisited: Changed stratigraphic allocation and new biozonation. First international petroleum conference & exhibition, Shiraz, Iran, 1-5.
Romero, J., Caus, E., & Rossel, J., 2002. A model for the paleoenvironmental distribiution of larger foraminifera based on late Eocene deposit on the margine of the south Pyrenean basin (SE Spain). Palaeogeography, Palaeoclimetology, Palaeoecology, 179: 43-56.                                                  
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., & Vincent, B., 2010. Regional stratigraphic architecture and reservoir types of the Oligo-Miocene deposits in the Dezful Embayment (Asmari and Pabdeh Formations) SW Iran. Geological Society of London, Special Publication, 329: 219–263.

Keywords

• Zagros Basin
• Interior Fars
• Asmari Formation
• Oligocene
• Biostratigraphy
• Paleoecology.‎

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References

اخزری، س.، صیرفیان، ع.، وزیری‌مقدم، ح.، 1394. ریزرخساره‌ها و مدل رسوبی سازند آسماری (الیگوسن) در شمال غرب روستای دریس (غرب استان فارس) و مقایسه ضخامت، سن و محیط رسوبی با سه برش دیگر در حوضه زاگرس. زمین‌شناسی نفت ایران، 9: 58ـ43.

آقانباتی، ع.، 1383. زمین‌شناسی ایران. سازمان زمین‌شناسی و اکتشاف معدنی، 586 ص.

خسروتهرانی، خ.، 1387. میکروپالئونتولوژی کاربردی، جلد اول: روزن‌داران. انتشارات دانشگاه تهران، 432 ص.

سازمان جغرافیایی نیروهای مسلح، 1384. نقشه کشور جمهوری اسلامی ایران، مقیاس 1:2000000.

وزیری‌مقدم، ح.، طاهری، ع.، کیمیاگری، م.، 1390. فرامینیفرا، جنس‌های شاخص و دیرینه بوم‌شناسی. انتشارات جهاد دانشگاهی واحد اصفهان، 372 ص.

Adams, T.D., & Bourgeois, F., 1967. Asmari biostratigraphy. Iranian Oil Operating Companies, Geological and Exploration Division, Unpublished Report No. 1074: 1-37.

Akhzari, S., Seyrafian, A., & Vaziri-Moghaddam, H., 2015. Oligocene ramp system (Asmari Formation) in the west of Fars province: Microfacies and sedimentary environment. National Conference on Novel Applied Researches, Urmia, 1: 60-61.

Allahkarampoor Dill, M., Seyrafian, A., & Vaziri-Moghadam, H., 2010. The Asmari Formation, north of the Gachsaran (Dill anticline), southwest Iran, facies analysis, depositional environments and sequence stratigraphy. Carbonate and Evaporites, 25 (2): 145-160.

Bassi, D., Hottinger, L., & Nebelsick, J.H., 2007. Larger foraminifera from the Upper Oligocene of the Venetian area, North-East Italy. Paleontology, 50 (4): 845-868.

Beavingtone-Penney, S.J., & Racey, A., 2004. Ecology of extant nummulitids and other larger benthic foraminifera: applications in palaeonvironmental analysis. Earth Science Reviews, 67 (3): 219-265.

Brandano, M., & Corda, L., 2002. Nutrients, sea level and tectonics: constraints for the facies architecture of a Miocene carbonate ramp in central Italy. Terra Nova, 14 (4): 257-262.

Ehrenberg, S.N., Pickard, N.A.H., Laursen, G.V., Monibi, S., Mossadegh, Z.K., Svana, T.A., Agrawi, A.A.M., Mc Arthur, J.M., & Thirlwall, M.F., 2007. Strontium isotope stratigraphy of the Asmari Formation (Oligocene – Lower Miocene), SW Iran. Journal of Petroleum Geology, 30: 107-128.

Farzipour-Saein, A., Yassaghi, A., Sherkati, S., & Koyi, H., 2009. Basin evolution of the Lurestan region in the Zagros fold and thrust belt, Iran. Journal of Petroleum Geology, 32: 5-19.

Flugel, E., 2010. Microfacies of Carbonate Rocks: Springer, 984 p.

Geel, H., 2000. Recognition of stratigraphic carbonate platform and slope deposits: empirical models based on microfacies analysis of Paleogene deposits in southeastern Spain. Paleogeography, Paleoclimatology, Paleoecology, 1550: 211-238.

Hottinger, L., 1983. Processes determining the distribution of larger foraminifera in space and time. Utrecht Micropaleontological Bulletins, 30: 239-253.

James, G.A., & Wynd, J.G., 1965. Stratigraphic nomenclature of Iranian oil consortium agreement area. American Association of Petroleum Geologists Bulletin, 49 (12): 2182-2245.

Laursen, G.V, Monibi, S., Allan, T.L., Pickard, N.A.H., Hosseiney, A., Vincent, B., Hamon, Y., Van Buchem, F.S.H., Moallemi, A., & Driullion, G., 2009. The Asmari Formation revisited: Changed stratigraphic allocation and new biozonation. First international petroleum conference & exhibition, Shiraz, Iran, 1-5.

MacQillan, H., 1975. Geological compilation map of Kharg - Ganaveh – Kazerun, 1: 250000 scale. Geological and Exploration Division Drawing, sheet No. 20512.

Renema, W., & Troelstra, S.R., 2001. Larger foraminifera distribution on a mesotrophic carbonate shelf in SW Sulawesi (Indonesia). Palaeogeography, Palaeoclimatology, Palaeoecology, 175 (1): 125-146.

Renema, W., 2002. Larger foraminifera as marine environmental indicators. Scripta Geology, 124: 1-260.

Romero, J., Caus, E., & Rossel, J., 2002. A model for the paleoenvironmental distribiution of larger foraminifera based on late Eocene deposit on the margine of the south Pyrenean basin (SE Spain). Palaeogeography, Palaeoclimetology, Palaeoecology, 179: 43-56.

Seyrafian, A., Vaziri-Moghaddam, H., Arzani, N., & Taheri, A., 2011. Facies analysis of the Asmari Formation in central and north-central Zagros basin, southwest Iran. Biostratigraphy, paleoecology and diagenesis. Revista Mexicana de Ciencias Geologicas, 28 (3): 439-458.

Soltanian, N., Seyrafian, A., & Vaziri-Moghaddam, H., 2011. Biostratigraphy and paleo-ecological implications in microfacies of the Asmari Formation (Oligocene), Naura anticline (Interior Fars of the Zagros Basin), Iran. Carbonates Evaporites, 26 (2): 167- 180.

Thomas, A.N., 1948. The Asmari limestone of southwest Iran: Report 706, (unpublished).

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., & Vincent, B., 2010. Regional stratigraphic architecture and reservoir types of the Oligo-Miocene deposits in the Dezful Embayment (Asmari and Pabdeh Formations) SW Iran. Geological Society of London, Special Publication, 329: 219–263.

Vaziri-Moghadam, H., Seyrafian, A., Taheri, A., & Motiei, H., 2010. Oligocene-Miocene ramp system (Asmari Formation) in the NW of Zagros Basin, Iran. Microfacies, paleoenvironment and depositional sequence: Revisita Mexicana de Ciencia Geologicals, 27: 56-71.

Wynd, J.G., 1965. Biofacies of the Iranian consortium-agreement area. Iranian Offshore Oil Company, Tehran, Report No. 1082: 1-80.