Conodonts of the Mississippian/Pennsylvanian boundary interval in Central Iran A. Bahrami a,⇑ , I. Boncheva b , P. Königshof c , M. Yazdi a , A. Ebrahimi Khan-Abadi a a Department of Geology, University of Isfahan, Isfahan 81746, Iran b Geological Institute, Bulgarian Academy of Sciences, Sofia 1113, Bulgaria c Senckenberg – Research Institute and Natural History Museum Frankfurt, Senckenberganlage 25, 60325 Frankfurt am Main, Germany article info Article history: Received 28 November 2013 Received in revised form 12 June 2014 Accepted 24 June 2014 Available online 9 July 2014 Keywords: Mississippian Pennsylvanian Conodont Central Iran abstract The record of conodonts related to the Mississippian/Pennsylvanian boundary interval was investigated in four sections in Central Iran from two different structural units. Two sections from the Sanandaj–Sirjan trend zone (Asad-abad, and Darchaleh sections) and two from the East-Central Iran Microplate (Shesh-angosht and Kale-Sardar sections) exhibit a nearly complete record previously described across the Mississippian/Pennsylvanian boundary in Iran. The investigated sections can be subdivided in three formations (Ghaleh-, Absheni-, and Zaluda Formation) which belong to the Sardar Group. The mid-Carboniferous boundary was defined by the occurrence of Declinognathus noduliferus s.l.. Bio-event characteristics of the Carboniferous conodont fauna (Mississippian genera Gnathodus and Lochriea have been replaced by Pennsylvanian genera Declinognathus and Idiognathodus) as well as sedimentological changes within overall shallow water deposits were located approximately 33° S of the paleoequator and suggest sea-level changes within the framework of the Late Paleozoic Ice Age (LPIA). Furthermore, a widespread crinoid marker horizon previously described from two localities in Iran can be subdivided into three units of different ages. Ó 2014 Elsevier Ltd. All rights reserved. 1. Introduction Four sections in Iran, each spanning the Mid-Carboniferous boundary interval were studied on the Sanandaj–Sirjan zone and on the East-Central Iran Microplate. During the Paleozoic, Iran was part of the northern margin of Gondwana. Marine conditions occurred in northern and Central Iran from the Middle Devonian to early Frasnian and persisted into the Early Pennsylvanian. A widespread uplift in the latest Carboniferous led to continental environments before the onset of a new marine cycle during the Early Permian. Major overviews on stratigraphy, facies patterns and paleogeography of the entire area of northern, central and southeastern Iran have been published by Wendt et al. (2002, 2005). The main Paleozoic successions of Central Iran occur in the North–South trending Tabas block which is bounded by the Kalmard strike-slip fault to the West and Naybandan fault to the East (Alavi, 1991, Fig. 1b). Carboniferous and Permian deposits in Central Iran occur most completely in the area of Tabas (Shotori range, Shirgesht area, and Ozbak-Kuh areas) and have been described earlier in a series of publications (Korn et al., 1999; Partoazar, 1995; Ruttner et al., 1968; Stepanov, 1971; Stöcklin, 1971; Stöcklin et al., 1965; Wendt et al., 2002; Wendt et al., 2005). The entire sequence of Carboniferous – Permian deposits is divided into three lithostratigraphic units: the Shishtu Formation (Devonian-Viséan), the Sardar Group (Viséan-earliest Permian) and the Jamal Formation (Permian). Recent fieldwork included sampling of the sediments yielded: (1) poorly studied fusulinids (Leven and Gorgij, 2006, 2007, 2009; Leven and Taheri, 2003; Leven and Vaziri, 2004; Leven et al., 2006; Sohrabi, 2006) and (2) detailed suite of conodont samples by Yazdi (1999) and Boncheva et al. (2007). According to Yazdi (1999) the Bahram For- mation is considered to be mainly of Frasnian age. The Shishtu For- mation reaches into the Viséan and is overlain by the Ghaleh Formation (Boncheva et al., 2007). The Late Palaeozoic Ice Age (LPIA) has been considered as one of the most prominent ice ages spanning much of Late Devonian to Permian time, when ice sheets waxed and waned across southern Gondwana (Veevers and Powell, 1987). It is clear that the LPIA con- sisted of several discreet icehouse climates with warmer periods of glacial minima. Intervals of glacial minima and maxima have been reported from low-latitudes (e.g., Bishop et al., 2009, 2010; Frakes et al., 1992; Heckel, 1986, 1994; Soreghan and Giles, 1999) as well as in high-latitudes (e.g., Caputo et al., 2008; Isbell et al., 2008a, http://dx.doi.org/10.1016/j.jseaes.2014.06.017 1367-9120/Ó 2014 Elsevier Ltd. All rights reserved. ⇑ Corresponding author. E-mail addresses: Bahrami_geo@yahoo.com (A. Bahrami), boncheva2005@ yahoo.com (I. Boncheva), peter.koenigshof@senckenberg.de (P. Königshof), meh. Yazdi@gmail.com (M. Yazdi), abramian22@gmail.com (A. Ebrahimi Khan-Abadi). Journal of Asian Earth Sciences 92 (2014) 187–200 Contents lists available at ScienceDirect Journal of Asian Earth Sciences journal homepage: www.elsevier.com/locate/jseaes