Investigating the paleoecological characteristics of Abtalkh Formation at Bahadorkhan Section (Central Kopet-Dagh) based on planktonic and benthic foraminifera

Document Type : Research Paper

Authors

1 ferdowsi university of Mashhad

2 ferdowsi University of Mashhad

Abstract

Study of a late Late Santonian to Late Campanian hemipelagic succession from Abtalkh Formation at the Bahadorkhan section (Central Kopet-Dagh) enabled us to verify paleoecology changes based on planktonic and benthic foraminifera assemblage. Bahadorkhan section is consisted of calcareous shale, lime marl, marl, and a few dispersed chalky limestone beds. Upper and lower boundaries of Abtalkh Formation are conformable with Abderaz and Neyzar formations. Since foraminifera are proper tools for paleoecological investigations, we used them in three methods to analyze the changes of paleobathymetry: 1) Van der Zwaan’s equations of determining depth and method (the ratio of planktonic foraminifera to benthic), 2) Leckie's morphotype model, and 3) investigating the changes of benthic foraminifera and the ratio of agglutinated benthic foraminifera to the utilized calcareous benthic foraminifera. Trox model (the ratio of epifaunal to infaunal (Ep/In)) was also used with the goal of identifying oxygen level and nutrients. According to the statistical counting, four stages of changes in depth and environmental conditions in this section with age range of late Late Santonian- Late Campanian were observed. According to the analysis, in the Early Campanian, P/B ratio and infaunal benthic are high which indicates the high level of water and eutrophic environment. In such an environment, nutrient and oxygen levels are respectively high and low. Then, at end of the Early Campanian and the beginning of Middle Campanian, water level decreases, and the environment moves toward oligotrophic conditions. During Middle Campanian and the early Late Campanian, water level increases again. Finally, during Late Campanian and along with the change of lithology to Neyzar Formation sandstones, we will witness the decrease of P/B ratio, water level drop, oxygen level increase, and nutrient decrease.

Keywords

Article Title [Persian]

بررسی شاخصه های بوم شناسی دیرینه سازند آب تلخ دربرش بهادرخان (کپه داغ مرکزی) برمبنای روزن داران شناور وکف زی

Authors [Persian]

  • محمد وحیدی نیا 2
  • عباس قادری 2
1
2 دانشگاه مشهد
Abstract [Persian]

مطالعه توالی زسوبات همی پلاژیک اواخر سانتونین پسین- کامپانین پسین سازند آب تلخ در برش بهادرخان (مرکز حوضه کپه داغ) ما را قادر ساخت تا براساس مجموعه روزن داران شناور و کف زی تغییرات بوم شناسی دیرینه را بررسی نماییم. سنگ شناسی برش بهادرخان متشکل از شیل آهکی، مارن آهکی، مارن و بصورت پراکنده چندین واحد سنگ آهک چاکی می باشد. وضعیت مرزهای زیرین و بالایی آن با سازندهای آبدراز و نیزارهمشیب و پیوسته است. از آنجا که روزن داران ابزار مناسبی برای بررسی های بوم شناسی دیرینه می باشند به منظور بررسی تغییرات عمق دیرینه از آنها به 3 روش استفاده شد: 1- معادلات تعیین عمق و روش Van derz van (نسبت روزن داران شناور به کف زی)(P/B، 2- مدل مورفوتایپی Leckie (1987) و 3- بررسی تغییرات پوسته روزن داران کف زی و نسبت روزن داران کف زی آگلوتینه به آهکی، همچنین با هدف بررسی میزان اکسیژن و مواد مغذی از مدل Trox نسبت روزن داران کف زی سطح زی به درون زی (Ep/In) استفاده شده است. بر اساس این شمارش های آماری 4 مرحله تغییرات عمق و شرایط محیطی را در این برش در محدوده سنی اواخرسانتونین پسین- کامپانین پسین مشاهده شد. طبق بررسیها در زمان کامپانین پیشین نسبت P/B و کف زی درون زی بالاست که این نشانه بالا بودن سطح آب و محیط یوتروفیک است که درچنین محیطی میزان اکسیژن کم و مواد مغذی بالا می باشد. سپس در اواخرکامپانین پیشین و ابتدای کامپانین میانی سطح آب پایین می آید و محیط به سمت شرایط الیگوتروفیک پیش میرود، طی کامپانین میانی و ابتدای کامپانین پسین سطح آب مجدداً افزایش می یابد و نهایتاً در زمان کامپانین پسین و با تغییر سنگ شناسی به ماسه سنگهای سازند نیزار ما شاهدکاهش در نسبت P/B و پایین آمدن سطح آب و افزایش در سطح اکسیژن وکاهش مواد مغذی می باشیم

Keywords [Persian]

  • سازند آب تلخ
  • بوم شناسی دیرینه
  • روزن داران شناور و کف زی
  • حوضه کپه داغ

References

Aghanabati, A., 2004. Geology of Iran. Geological survey of Iran, 568 p.
Ahmadi, M., Vahidinia, M., Ashouri, A.R., 2013. Paleoecology of Abtalkh Formation based on planktonic and benthic foraminifera in Padeha section, Kopet-Dagh Basin. Sedimentary Facies. 5(2): 119-134 (in Persian).
Alegret, L., & Thomas, E., 2001. Upper Cretaceous and Lower Paleogene benthic foraminifera from northeastern Mexico. Micropaleontology. 47: 269-316.
Alegret, L, Molina, E, Thomas, E., 2003. Benthic foraminiferal turnover across the Cretaceous/Paleogene boundary at Agost (southeastern Spain): paleoenvironmental inferences. Marine Micropaleontology. 48: 251-279.
Aubert, J. & Berggren, W. A. 1976. Paleocene benthic foraminiferal biostratigraphy and paleoecology of Tunisia. Bulletin des Centre de Recherches, Pau-SNPA .10 : 379-469.
Berger, W.H., Diester-Haass, L., 1988.  Paleoproductivity: the benthic / planktonic ratio in foraminifera as a productivity index. Marine Geology. 81: 15 -25.
Caron, M., Homewood, P. 1983. Evolution of early planktic foraminifers. Mar. Micropaleontology. 7: 435–462.
Cushman, J. A., 1946.Upper Cretaceus foraminifera of the Gulf coastal region of the United States and adjacent area. United States Geol. Sur. Prof, 241pp.
Eicher, D.L., 1969. Cenomanian & Turonian planktonic foraminifera from the Western Interior of the United States. In: Bronni- mann, P. ,  Renz, H. H. (Eds. ), Proceedings of the First International Conference on Planktonic Microfossils, E. J. Brill, Leiden. 2: 163–174.
Ghoorchaei, S., Vahidinia, M., Ashoori, A., 2012. Late Maastrichtian benthic foraminiferal response to palaeoenvironmental changes: a case study from the AbTalkh Formation, west of Kopeh-Dagh Basin, Iran,.P:.25-42
Hadavi, F., 2004. Calcareous nannofossils from the Abtalkh Formation (Campanian-Maastrichtian), Kopet-Dagh range, NE Iran. Journal of Nannoplankton Research. 26(1): 63-68.
Hadavi, F., Khodadadi, L., 2002. Calcareous nannoplankton of the Campanian-Maastrichtian of NE Iran. Journal of Nannoplankton Research. 24(2):109.
Hadavi, F., Notghi Moghaddam, M., 2002. Calcareous nannofossils from the Chalky Limestone in the Kopet-Dagh range, NE Iran. Journal of Nannoplankton Research. 24(2): 110.
Holbourn, A., Kuhnt W., Soeding E. 2001: Atlantic paleobathymetry, paleoproductivity and paleocirculation in the late Albian: the benthic foraminiferal record. Palaeogeogr. Palaeoclimatol. Palaeoecol. 170: 171-196.
Honarmand, A., Vahidinia, M., Ghaderi, A. 2015: Lithostratigraphic correlation and Biostratigraphic of the Abtalkh Formation at the Bahadorkhan section (Central Kopet-Dagh) based on planktonic foraminifera. Paleontology. 3(1) (in press), (in Persian).
Jorissen, F.J., Fontanier, C., Thomas, E., 2007. Paleoceanographical proxies based on deep-sea benthic foraminiferal assemblage characteristics. In: Proxies in Late Cenozoic Pale oceanography (Pt.2): Biological tracers & biomarkers, edited by C. Hillaire-Marcel & A. de Vernal, Elsevier, pp 843.
Keller, G. 1988. Biotic turnover in benthic foraminifera across the Cretaceous/Tertiary boundary at El Kef, Tunisia. Paleogeography, Palaeoclimatology. Palaeoecology 66, 153-171.
Keller, G. 1992. Paleoecological response of Tethyan benthic foraminifera to the Cretaceous-Trtiary boundary transition. In studies in benthic foraminifera, Benthos, 90 (eds Takagayanagi, Y. & Saito, T.), pp.77-91 (Tokyo University Press, Tokyo).
Leckie, R.M., 1987. Paleoecology of mid-Cretaceous planktonic foraminifera: A comparison of open ocean & Epicontinental Sea assemblages. Micropaleontology. 33: 164–176.
Berggren, W.A., Aubert J. 1975: Paleocene benthonic foraminiferal biostratigraphy, paleobiogeography and paleoecology of Atlantic-Tethyan regions: Midway-type fauna. Palaeogeogr. Palaeoclimatol. Palaeoecol. 18: 73-192.
Li, L., Keller, G., Adatte, T., Stinnesbeck, W., 2000. Late Cretaceous sea-level change in Tunisia: a multidisciplinary approach. Journal of the Geological Society, London. 157: 447-458.
Lüning, S., Marzouk,  A.M., Morsi, A.M., Kuss, J., 1998. Sequence stratigraphy of the Upper Cretaceous of south-east Sinai, Egypt. Cretaceous Research. 19: 153- 196.
Nagy, J., Finstad E.K., Dypvik, H., Bremer, M.G.A. 2001: Response of foraminiferal facies to trasgressive-regressive cycles in the Callovian of northest Scotland. J. Foram. Res. 31: 324–349.
Nyazi, M., Vahidinia, M.,­­ Ashouri, A.R., 2013. Microbiostratigraphy and Paleoecology of the Abtalkh Formation based on foraminifera at Qareh-Sou section (Southwest of Kalat-e-Naderi, NE Iran). Sedimentary Facies 6(1), 95-114 (in Persian).
Premoli-Silva, I., Sliter, W.V., 1999. Cretaceous pale oceanography: evidence from planktonic foraminiferal evolution. Geology. Soc Am. Spec. 332: 301–328.
Sliter, W. V. & Baker, R. A. 1972. Cretaceous bathymetric distribution of benthic foraminifers. Journal of Foraminiferal Research. 2:167-183.
Vahidinia, M., 2007. The biostratigraphy of deposits in Kopet-Dagh Basin during Senonian to Maestrichtian. Shahid Beheshti University (Unpublished PhD. Thesis in Persian).671pp.
Van der Zwaan, G.J., Jorissen, F.J., De Stigter, H.C., 1990; the depth-dependency of planktonic / benthic foraminiferal rations; constraints & applications, Marine Geology. 95: 1–16.
Cushman, J.A., 1946. Upper Cretaceous foraminifera of Gulf coastal region of the United States and adjacent area. United States Geo. Sur. Prof. 206: 1-241.
Van der Zwaan, G.J., Duijnstee, I.A.P., Den Dulk, M., Ernst, S.R., Kouwenhoven, N.T., 1999. Benthic foraminifers: proxies or problems A review of paleoecological concepts. Earth Sci. Rev. 46: 213-236.
Van Morkhoven, F.P.C.M., Berggren, W.A., Edwards, A.S., 1986. Cenozoic cosmopolitan deep water benthic foraminifera. Elf-Aquitanian, pau.
Velic, I., 2007. Stratigraphy and Palaeobiogeography of Mesozoic Benthic Foraminifera of the Karst Dinarides (SE Europe). Geologia Croatica. 1-113.
Wright, R.G., 1977. Planktonic-benthonic ratio in Foraminifera as paleobathy metrictool:quantitative evaluation. Annu. AAPG and Soc. Econ. Paleontol. Mineral. Conv., Washington, D. C., 65.
Geopersia
Volume 6, Issue 1 - Serial Number 22287825
Winter and Spring
March 2016
Pages 117-128

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History

  • Receive Date: 22 November 2015
  • Revise Date: 29 May 2016
  • Accept Date: 26 June 2016

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