Journal of the Geological Society , London, Vol. 161, 2004, pp. 513–522. Printed in Great Britain. 513 Early Cambrian location and affinities of the Brunovistulian terrane (Central Europe) in the light of palaeomagnetic data J. NAWROCKI 1 , A. Z ˙ YLIN ´ SKA 2 , Z. BULA 3 , J. GRABOWSKI 1 , P. KRZYWIEC 1 & P. POPRAWA 1 1 Polish Geological Institute, Rakowiecka 4, 00-975 Warsaw, Poland (e-mail: jnaw@pgi.waw.pl) 2 Department of Geology, University of Warsaw, Zwirki iWigury 93, 02-089 Warsaw, Poland 3 Upper Silesian Branch, Polish Geological Institute, Kro ´lowej Jadwigi 1, 41-200 Sosnowiec, Poland Abstract: The Brunovistulian was one of the first tectonic units of Central Europe to be defined as a ‘terrane’. In spite of extensive studies, the Early Palaeozoic palaeogeographical position and provenance of this unit remains unclear. A palaeomagnetic study of the Lower Cambrian red beds and a study of the trilobite fauna were performed to provide constraints on the palaeogeographical position of the terrane in Early Cambrian time. Good quality palaeomagnetic data obtained from the Lower Cambrian red beds suggest the mixed nature of the Early Cambrian geomagnetic field and a nearly equatorial position (a palaeolatitude of c.78) of the Brunovistulian terrane in the Early Cambrian. Comparison of this palaeolatitude with existing palaeogeo- graphical models leads to the conclusion that at this time the Brunovistulian terrane was separated by a great distance from the Avalonian margin of Gondwana. The terrane was located within the Cadomian belt, occupying a position north of the present-day northern margin of Africa. It was coupled to the present-day southern margin of Baltica during the Cambrian, when Baltica moved along the Cadomian margin of Gondwana. Another possibility is that the Brunovistulian terrane could have remained near this margin of Baltica since Grenvillian time and was incorporated into the Cadomian orogen. Keywords: Brunovistulian terrane, Cambrian, palaeogeography, palaeomagnetism, trilobite fauna. The Brunovistulian terrane (e.g. Dudek 1980; Poz ˙aryski 1991; Dadlez 1995; Bula et al. 1997) is situated near the southwestern edge of the East European Craton, in the area of the Trans- European Suture Zone (Fig. 1). It was one of the first tectonic units of Central Europe to be defined as a ‘terrane’ (Brochwicz- Lewin ´ski et al. 1986) and still remains the best documented terrane of the central part of the Trans-European Suture Zone (Poz ˙aryski 1991; Dadlez 1995; Franke 1995; Pharaoh 1999). An exotic position of the Brunovistulian terrane with respect to the East European Craton, as well as to the Malopolska and Bohemian Massifs during the early Palaeozoic, is suggested by the composition of the basement (Dudek 1980), the development of sedimentary cover (Bula et al. 1997; Bula 2000), and the presence of major wrench zones, which border the Brunovistu- lian terrane, particularly in the north and east (Z ˙ aba 1999; Bula 2000). The researchers postulating an allochthonous origin for the Brunovistulian terrane interpreted it as a fragment of the crust derived from the Gondwanan margin. This was based on the general geological framework (Unrug et al. 1999), faunal provincialism (Moczydlowska 1997), the results of provenance studies of detrital minerals (Belka et al. 2000), Nd model ages and the age of single zircon grains from the basement (Finger et al. 2000a, b; Hegner & Kro ¨ner 2000; Friedl et al. 2001). According to these interpretations of the Brunovistulian terrane as an allochthonous terrane, it was located in the peri-Gondwa- nan belt during the Neoproterozoic–Early Cambrian, in its South American (Hegner & Kro ¨ner 2000; Friedl et al. 2001) or North African region (Unrug et al. 1999; Leichman & Ho ¨ck 2001). A more stationary model was presented by Z ˙ elaz ´niewicz (1998) and Z ˙ elaz ´niewicz et al. (2001), who suggested, on the basis of U–Pb sensitive high-resolution ion microprobe (SHRIMP) data, that the Neoproterozoic (Vendian) foreland flysch basin of the Brunovistulian terrane and neighbouring Malopolska block was developed next to the East European Craton. The basement of the Brunovistulian terrane is composed of metamorphic and igneous rocks, mostly Cadomian (Neoproter- ozoic) in age (Dudek 1980; Van Breemen et al. 1982; Finger et al. 2000a, b;Z ˙ elaz ´niewicz et al. 2001). In some places they are covered by Vendian greenschist-grade metasediments (Z ˙ elaz ´niewicz et al. 2001). The Cadomian basement of the Brunovistulian terrane is overlain by gently deformed Lower Cambrian to Ordovician unmetamorphosed sedimentary rocks (Bula 2000). The chronostratigraphy of the Lower Cambrian clastic sediments, which in the northern part of the Brunovis- tulian terrane continue into the Middle Cambrian and Ordovi- cian units, is based on acritarch and trilobite fauna (Orlowski 1975; Moczydlowska 1995, 1997; Jachowicz & Prˇichystal 1998). These sediments are subdivided into two lithostrati- graphic units: an older Borze ¸ta Formation and a younger Goczalkowice Formation (Fig. 1c) (Bula et al. 1997). The sediments of the Borze ¸ta Formation are recognized only along the eastern margin of the Brunovistulian terrane, with a maximum thickness of about 1000 m. The thickness of the Goczalkowice Formation increases from the SW to the east and north, and is estimated to be up to c. 2000 m in the marginal part of the Brunovistulian terrane. The basal sequence of the Cambrian, i.e. the Mogilany Member of the Goczalk- owice Formation, consists of hematitic quartzo-feldspathic sandstones, and pebbly sandstones. The remaining part of the Cambrian sequence represents a complete marine transgressive cycle, which follows terrestrial deposition of the basal se- quence (Moczydlowska 1997). The Lower Palaeozoic rocks of the Brunovistulian terrane are covered by Lower Devonian sandstones of the ‘old red’ type (Konior & Turnau 1973). They were succeeded by the develop- ment of thick carbonate cover that accumulated up to Vise ´an time (Narkiewicz 1978; Belka 1985), followed by Vise ´an flysch sediments in the western part of the Brunovistulian terrane