Late Cretaceous to Early Paleogene global sea level fluctuations and the sedimentary environment in central Alborz (Nort
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ORIGINAL PAPER
Late Cretaceous to Early Paleogene global sea level fluctuations and the sedimentary environment in central Alborz (Northern Iran) Javad Rabbani 1 & Reza Emamgholi 2 & Nasrollah Abbassi 1 & Mohammad Saeed Shariatzadeh 3 Received: 17 July 2019 / Accepted: 14 November 2020 # Saudi Society for Geosciences 2020
Abstract The Cretaceous-Paleogene sequence, including K-Pg transition, located 45 km from the South of Sari in the North of Iran was analyzed in regards to lithology, lithofacies, foraminifera, and palynology evaluation. The main aim of this study was the reconstruction of sedimentary environmental condition including relative sea level changes during the K-Pg transition. Seventy rock samples were collected from 133 m of sedimentary rocks, mainly comprising limestone, sandstone, siltstone, and evaporate. Two species of foraminifera, ten species of spore, and seven species of pollen grains have been identified. K/ Pg boundary has been determined based on the first occurrence of Tricolpites phillipsii in the 133 m above the base of the studied section. Two palynofacies have been identified based on statistical analysis of palynofacies factors (SOM, MP, Ph). Palynofacies analysis suggests nearshore (inner ramp) as a sedimentary environment for these sequences. Our palynofacies data indicate sealevel regression near K/P which can be correlated to the global sea level trend. Keywords K/Pg boundary . Sea-level change . Sedimentary environment . Alborz Basin . Iran
Introduction The Alborz Mountains, forming a gently sinuous eastwest range across northern Iran south of the Caspian Sea, constitute a northern part of the Alpine-Himalayan orogeny from western Asia (Stöcklin 1974). The Upper Cretaceous sequence in the Alborz Mountain is composed of marine calcareous marl but displays various facies
Responsible Editor: Beatriz Badenas * Javad Rabbani [email protected] Reza Emamgholi [email protected] Nasrollah Abbassi [email protected] Mohammad Saeed Shariatzadeh [email protected] 1
Geology Department, University of Zanjan, Zanjan, Iran
2
University of Zanjan, Zanjan, Iran
3
The Khazar Exploration and Production Company (Kepco), Tehran, Iran
between the West and the East of Alborz. At the base of the Paleogene, a polygenic, basal conglomerate unconformably overlies the Mesozoic formations in the Southern Alborz. In the North, the Lower Paleogene shallow marine sediments conformable overlie the Cretaceous carbonates (Rezaeian 2009). Cretaceous-Paleogene strata is well exposed in the Northern Alborz (South of Sari) near Shahid Rajaee dam. Few paleontological studies had been carried out in this area including Miocene vertebrate fossils from takam area (Stehlin 1931) and a report from vertebrate footprints in the Shahid Rajaee dam district (Ataabadi and Abbassi 2007). The Neogene sediments of the northern Alborz Mountains show high potential for hydrocarbon detection (Mohajer Soltani and Shariat Zadeh 1393). This study is concerned about relative dating and reconstruction of sedimentary
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