Univrsity of Tehran Press Geopersia 2228-7817 12 2 2022 12 05 Biostratigraphy of Paleocene strata based on calcareous nannofossils at Zard-Darreh section, southern central Alborz Mountains, Northern Iran - 299 316 87710 10.22059/geope.2022.333947.648641 EN Fariba Foroughi Department of Geology, Faculty of Sciences, University of Tehran, Tehran, Iran. Hadi Ghadim Khatoon Abad Department of Geology, Faculty of Sciences, University of Tehran, Tehran, Iran. Hossein Kamyabi Shadan Exploration Directorate of the National Iranian Oil Company, Tehran, Iran. Journal Article 2021 11 14 <span dir="ltr" style="left: 154.5px; top: 805.585px; font-size: 17.2172px; font-family: serif; transform: scaleX(1.00262);" role="presentation"><span dir="ltr" style="left: 154.5px; top: 488.187px; font-size: 17.2172px; font-family: serif; transform: scaleX(0.994856);" role="presentation">The study area is located in the Zard-Darreh</span><span dir="ltr" style="left: 457.235px; top: 488.187px; font-size: 17.2172px; font-family: serif;" role="presentation"> </span><span dir="ltr" style="left: 461.599px; top: 488.187px; font-size: 17.2172px; font-family: serif; transform: scaleX(0.999388);" role="presentation">village nearby Damavand city in the eastern part of Tehran</span> <span dir="ltr" style="left: 154.5px; top: 507.987px; font-size: 17.2172px; font-family: serif; transform: scaleX(1.02397);" role="presentation">province. Late Cretaceous strata are well-exposed in the Zard-Darreh</span><span dir="ltr" style="left: 642.185px; top: 507.987px; font-size: 17.2172px; font-family: serif;" role="presentation"> </span><span dir="ltr" style="left: 647.999px; top: 507.987px; font-size: 17.2172px; font-family: serif; transform: scaleX(1.01474);" role="presentation">village, comprising siliciclastic</span> <span dir="ltr" style="left: 154.5px; top: 527.886px; font-size: 17.2172px; font-family: serif; transform: scaleX(1.06477);" role="presentation">sediments with limestone stringers, which are overlain by red conglomerate deposits of the Fajan</span> <span dir="ltr" style="left: 154.5px; top: 547.686px; font-size: 17.2172px; font-family: serif; transform: scaleX(1.01734);" role="presentation">Formation. This study was carried out on a 96 m interval of the K3 and Fajan Formation to determine</span> <span dir="ltr" style="left: 154.5px; top: 567.586px; font-size: 17.2172px; font-family: serif; transform: scaleX(1.04187);" role="presentation">the precise age of the sampling interval. Eighty-nine surface samples were collected and treated for</span> <span dir="ltr" style="left: 154.5px; top: 587.385px; font-size: 17.2172px; font-family: serif; transform: scaleX(1.00128);" role="presentation">calcareous nannofossils. 53 species (27 genera) and 15 families were identified and nine biozones were</span> <span dir="ltr" style="left: 154.5px; top: 607.185px; font-size: 17.2172px; font-family: serif; transform: scaleX(1.01514);" role="presentation">established. Biozone CC20/UC15b</span>^{<span dir="ltr" style="left: 399.5px; top: 604.845px; font-family: serif; transform: scaleX(0.999151);" role="presentation">TP</span>}<span dir="ltr" style="left: 412.322px; top: 604.845px; font-size: 11.0073px; font-family: serif;" role="presentation"> </span><span dir="ltr" style="left: 416.6px; top: 607.187px; font-size: 17.2172px; font-family: serif; transform: scaleX(1.04763);" role="presentation">occurs in the lowermost part of the K3 and represents the Late</span> <span dir="ltr" style="left: 154.501px; top: 627.087px; font-size: 17.2172px; font-family: serif; transform: scaleX(1.06522);" role="presentation">Cretaceous (Campanian) age. The NP1 to NP8 biozones are present the rest of the study interval,</span> <span dir="ltr" style="left: 154.501px; top: 646.887px; font-size: 17.2172px; font-family: serif; transform: scaleX(1.07112);" role="presentation">suggesting Early Paleocene (Danian-Thanetian) age. Based on calcareous nannofossils the Early</span> <span dir="ltr" style="left: 154.501px; top: 666.786px; font-size: 17.2172px; font-family: serif; transform: scaleX(0.99907);" role="presentation">Paleocene is recorded for the first time in the Zard-Darreh village in the Alborz Mountains. Likewise, a</span> <span dir="ltr" style="left: 154.501px; top: 686.586px; font-size: 17.2172px; font-family: serif; transform: scaleX(1.08142);" role="presentation">hiatus exists between the Late Cretaceous </span><span dir="ltr" style="left: 591px; top: 686.587px; font-size: 17.2172px; font-family: serif; transform: scaleX(1.10881);" role="presentation"><span dir="ltr" style="left: 154.501px; top: 686.586px; font-size: 17.2172px; font-family: serif; transform: scaleX(1.08142);" role="presentation">(CC20/UC15b</span>^{<span dir="ltr" style="left: 578.2px; top: 684.245px; font-family: serif; transform: scaleX(0.991346);" role="presentation">TP</span>}<span dir="ltr" style="left: 590.922px; top: 684.245px; font-size: 11.0073px; font-family: serif;" role="presentation"> </span><span dir="ltr" style="left: 591px; top: 686.587px; font-size: 17.2172px; font-family: serif; transform: scaleX(1.10881);" role="presentation">) </span> and Early Paleocene (NP1), which</span> <span dir="ltr" style="left: 154.5px; top: 706.387px; font-size: 17.2172px; font-family: serif; transform: scaleX(1.01743);" role="presentation">encompasses the Maastrichtian stage and part of Early Paleocene. Finally, some small size <em>calcareous</em></span><em> </em><span dir="ltr" style="left: 154.5px; top: 726.187px; font-size: 17.2172px; font-family: serif; transform: scaleX(0.994466);" role="presentation"><em>nannofossils</em> such as</span><span dir="ltr" style="left: 294.223px; top: 726.187px; font-size: 17.2172px; font-family: serif;" role="presentation"> </span><span dir="ltr" style="left: 298.1px; top: 726.187px; font-size: 17.2172px; font-family: serif; transform: scaleX(1.00817);" role="presentation"><em>Biantholithus sparsus</em>, <em>Cruciplacolithus primus</em>, <em>Cruciplacolithus intermedius</em>,</span><span dir="ltr" style="left: 836.763px; top: 726.187px; font-size: 17.2172px; font-family: serif;" role="presentation"> </span><span dir="ltr" style="left: 840.799px; top: 726.187px; font-size: 17.2172px; font-family: serif; transform: scaleX(0.994343);" role="presentation">and </span><span dir="ltr" style="left: 154.5px; top: 746.086px; font-size: 17.2172px; font-family: serif; transform: scaleX(1.00573);" role="presentation">Cruciplacolithus asymmetricus</span><span dir="ltr" style="left: 369.324px; top: 746.086px; font-size: 17.2172px; font-family: serif;" role="presentation"> </span><span dir="ltr" style="left: 374.1px; top: 746.086px; font-size: 17.2172px; font-family: serif; transform: scaleX(1.0045);" role="presentation">are present in the NP1 biozone of Early Paleocene, which may indicate</span> <span dir="ltr" style="left: 154.5px; top: 765.886px; font-size: 17.2172px; font-family: serif; transform: scaleX(1.08764);" role="presentation">the effect of various environmental factors. Furthermore, some calcareous nannofossils such as</span> <em><span dir="ltr" style="left: 154.5px; top: 785.786px; font-size: 17.2172px; font-family: serif; transform: scaleX(0.986992);" role="presentation">Sphenolithus</span></em><span dir="ltr" style="left: 243.198px; top: 785.786px; font-size: 17.2172px; font-family: serif;" role="presentation"> </span><span dir="ltr" style="left: 248.7px; top: 785.786px; font-size: 17.2172px; font-family: serif; transform: scaleX(1.01546);" role="presentation">spp. and</span><span dir="ltr" style="left: 306.92px; top: 785.786px; font-size: 17.2172px; font-family: serif;" role="presentation"> </span><em><span dir="ltr" style="left: 311.999px; top: 785.786px; font-size: 17.2172px; font-family: serif; transform: scaleX(1.02173);" role="presentation">Discoaster mohleri</span></em><span dir="ltr" style="left: 445.284px; top: 785.786px; font-size: 17.2172px; font-family: serif;" role="presentation"> </span><span dir="ltr" style="left: 450.599px; top: 785.786px; font-size: 17.2172px; font-family: serif; transform: scaleX(1.02269);" role="presentation">are present in NP6 and NP7 biozones of the study area that</span> <span dir="ltr" style="left: 154.5px; top: 805.585px; font-size: 17.2172px; font-family: serif; transform: scaleX(1.00262);" role="presentation">may indicate a warning climatic condition toward the Eocene.</span></span> https://geopersia.ut.ac.ir/article_87710_7c9ae1d51bc008a861793150117bc0d0.pdf