Magnetostratigraphy of Permian/Triassic boundary sequences in the Cis-Urals, Russia: No evidence for a major temporal hiatus Graeme K. Taylor a, ⁎, Christopher Tucker a , Richard J. Twitchett a , Timothy Kearsey a , Michael J. Benton b , Andrew J. Newell c , Mikhail V. Surkov d , Valentin P. Tverdokhlebov d a School of Earth, Ocean and Environmental Sciences, University of Plymouth, Drake Circus, Plymouth PL4 8AA, UK b Department of Earth Sciences, University of Bristol, Bristol BS8 1RJ, UK c British Geological Survey, MacLean Building, Wallingford OX10 8BB, UK d Geology Institute of Saratov State University, Astrakhanskaya 83, 410075 Saratov, Russia abstract article info Article history: Received 6 June 2008 Received in revised form 3 February 2009 Accepted 6 February 2009 Available online 5 March 2009 Editor: R.D. van der Hilst Keywords: Magnetostratigraphy Permian–Triassic boundary Russia Tatarian During the last five years there has been considerable doubt over the age of the continental uppermost Permian Russian stages, the Kazanian and Tatarian. Traditionally they have been regarded as Late Permian but were re-dated as Middle Permian in the 2004 international time scale, despite fossil evidence that the Tatarian, at least, is Late Permian. These debated ages are tested by magnetostratigraphic study of five sections spanning the Permian Triassic Boundary (PTB) of the SE Urals in the Orenburg region of Russia. The Upper Permian and Lower Triassic of this region have a well documented vertebrate fauna whose evolution has a significant bearing on our understanding of the PTB mass extinction event. If the Tatarian is viewed as Mid Permian, then the Late Permian in Russia is marked by a 9–10 Ma stratigraphic gap. The palaeomagnetic data yield a distinct series of polarity zones that provide clear local and regional correlation and are readily tied to a recently compiled global magnetostratigraphic record. On the basis of this correlation the sampled sections span the upper Guadalupian to Induan stages without any obvious break, so confirming the traditional view that the Tatarian is Late Permian in age. Anomalies in the magnetic inclination are consistent with sediment compaction (inclination shallowing, a common phenomenon of red beds) but declination anomalies between these sites and elsewhere in Russia may suggest localised vertical axis rotation. © 2009 Elsevier B.V. All rights reserved. 1. Introduction The Late Permian mass extinction event is regarded as the greatest single extinction event in geological history with an estimated loss of 80–90% of marine species (Benton, 2003). Our knowledge of this event has grown significantly in recent years (Twitchett, 2006) following stratigraphic research of marine Permian–Triassic strata associated with identification of the base-Triassic GSSP (Global Boundary Stratotype Section and Point), which is accepted as the first appearance datum of the conodont Hindeodus parvus, in Meishan, South China (Yin et al., 2001). Our understanding of the extinction event in the terrestrial realm is, however, relatively poor. A key problem is the dating and correlation of the terrestrial deposits. Hitherto, the main correlative tool for Permian continental successions has been a fossil vertebrate-based biostrati- graphic scheme derived from the study of the Karoo Supergroup in South Africa (Rubidge, 1995; Lucas, 2006). However, these biozones cannot be directly correlated with marine stratigraphy, and phylogenetic problems with some of the key zonal taxa (e.g. Dicynodon), may limit their use in global correlation (Angielczyk and Kurkin, 2003). Attempts to establish a stratigraphic system based on carbon isotopes have proved difficult because of the non-global nature of some carbon isotope excursions (Tabor et al., 2007). Magnetostratigraphy is an attractive alternative to these approaches as it utilises the globally synchronous nature of magnetic reversals and is, essentially, a facies-independent technique. It does however rely upon the construction of a coherent and composite magnetostratigraphic record, linked to biostratigraphy, and significant progress has been made toward a global, composite Permian/ Triassic boundary (PTB) record (Gallet et al., 2000; Scholger et al., 2000; Molostovskii, 2005; Steiner, 2006; Szurlies, 2007). Most studies of the late Permian mass extinction event in the terrestrial realm have focussed on the southern palaeohemisphere, in particular South Africa, Australia and Antarctica (Smith and Ward, 2001). To test whether trends and patterns of extinction recorded in these studies are truly global, we have studied the Permian–Triassic record of northern palaeohemisphere sections in Russia (Benton, 2003; Tverdokhlebov et al., 2005). However, in order to integrate the rich and diverse fossil tetrapod assemblages of this region (Tverdokh- lebov et al., 1997; Tverdokhlebov et al., 2002; Tverdokhlebov et al., 2005; Surkov et al., 2007) into global estimates of species loss at this critical extinction event, it is necessary to demonstrate how the Russian sequences correlate with the global stratigraphic scheme. It Earth and Planetary Science Letters 281 (2009) 36–47 ⁎ Corresponding author. Tel.: +44 1752 584770; fax: +441752 584776. E-mail address: GTaylor@plymouth.ac.uk (G.K. Taylor). 0012-821X/$ – see front matter © 2009 Elsevier B.V. All rights reserved. doi:10.1016/j.epsl.2009.02.002 Contents lists available at ScienceDirect Earth and Planetary Science Letters journal homepage: www.elsevier.com/locate/epsl