Planktonic foraminiferal-based Biostratigraphy of Upper Cretaceous deposits with emphasis on the Cenomanian-Turonian and Cretaceous-Paleogene boundaries in the northeastern part of the Kabirkuh anticline, southeastern Ilam
Subject Areas : stratigraphySakineh Arefifard 1 , Noshin Moradi Lirkashasi 2 , Thomas Algeo 3 , Jonathan Schueth 4 , Lei Zhang 5
1 - Associate professor of Geology Department, Basic Sciences Faculty, Lorestan University, Khorramabad, Iran
2 - Geology Department, Lorestan University, Khorramabad, Lorestan 68151-44316, Iran
3 - Department of Geosciences, University of Cincinnati, Cincinnati, USA
4 - Department of Geography/Geology, University of Nebraska Omaha, Omaha, USA
5 - Department of Geosciences, China University of Geosciences, Wuhan, Chinana
Keywords: Upper Cretaceous biostratigraphy, planktonic foraminifera, Kabirkuh Anticline, southeastern Ilam,
Abstract :
In this study, the biostratigraphy of Upper Cretaceous deposits in the Pakal-e Garab section—with a thickness of 708 meters—located in the northeastern part of the Kabirkuh anticline, southwestern Iran, is investigated. This stratigraphic succession includes the Sarvak, Surgah, Ilam, and Gurpi formations, as well as the basal part of the Pabdeh Formation. To conduct a detailed biostratigraphic analysis and assess the diversity and distribution of planktonic foraminiferal fauna in the Upper Cretaceous deposits, the 708-meter-thick Pakal-e Garab section was studied. The investigation led to the identification of 24 genera and 75 species of planktonic foraminifera. Based on the recognized microfossils, 16 biozones and 2 sub-biozones were identified. According to these biozones, the age of the Sarvak Formation is assigned to the early Cenomanian to middle Turonian, the Surgah Formation to the Late mid Turonian to earliest Santonian, the Ilam Formation to the early Santonian to early–middle Campanian, and the Gurpi Formation to the middle Campanian to late Maastrichtian. At the base of the Pabdeh Formation, a 5-meter-thick purple shale containing diagnostic Paleocene fauna was identified, suggesting a Danian age for this part of the section. This study also presents evidence for the impact of the Oceanic Anoxic Event 2 (OAE2) at the Cenomanian–Turonian boundary and the end-Cretaceous mass extinction at the K/Pg boundary on the planktonic foraminiferal communities in the Pakal-e Garab section. These events are reflected in reduced diversity and significant changes in the faunal assemblages.
- ALAVI, M., 2004, Regional stratigraphy of the Zagros fold-thrust belt of Iran and its proforeland evolution: American Journal of Sciences, 304, 1-20.
- ARENILLAS, I., ARZ, J.A. and GILABERT, V., 2018, Blooms of aberrant planktic foraminifera across the K/Pg boundary in the Western Tethys: Causes and evolutionary implications: Paleobiology, 44(3), 460-489.
- ARTHUR, M.A., SCHLANGER, S.T. and JENKYNS, H.C., 1987. The Cenomanian-Turonian Oceanic Anoxic Event, II. Palaeoceanographic controls on organic-matter production and preservation: Geological Society, London, Special Publications, 26(1), 401-420.
- BOLLI, H.M., SAUNDERS, J. B. and PERCH-NIELSEN, K., 1985, Plankton stratigraphy, Vol. I., Cambridge University Press, Cambridge, 87-154.
- CARON, D.A., MICHAELS, A.F., SWANBERG, N.R. and HOWSE, F.A., 1995, Primary productivity by symbiont-bearing planktonic sarcodines (Acantharia, Radiolaria, Foraminifera) in surface waters near Bermuda: Journal of Plankton Research, 17(1), 103-129.
- CHANG, B., HUANG, J., ALGEO, T.J., PANCOST, R.D., WAN, X., XUE, Y., JIA, J., WANG, Z., HU, J., WANG, J. and WANGg, S., 2022, Episodic massive release of methane during the mid-Cretaceous greenhouse: GSA Bulletin, 134(11-12), 2958-2970.
- CHOARENZA, A.A., FARNSWORTH, A., MANNION, P.D., LUNT, D.J., VALDES, P.J., MORGAN, J.V. and ALLISON, P.A., 2020, Asteroid impact, not volcanism, caused the end-Cretaceous dinosaur extinction: Proceedings of the National Academy of Sciences, 117(29), 17084-17093.
