A new lower Cambrian eodiscoid trilobite fauna from Swedish Lapland and its implications for intercontinental correlation

Abstract

A lower Cambrian eodiscoid trilobite fauna and an associated holmiid trilobite,Holmiasp., are described from a bioclastic limestone at the top of the Torneträsk Formation in the Luobákti section, south of Lake Torneträsk, northern Sweden. Other associated polymerid trilobites includeOrodes?lapponicaandStrenuaeva inflata. The precise age of the trilobite fauna cannot be determined, but its generic composition and stratigraphical position at the top of the lower Cambrian suggest that it was recovered from theOrnamentaspis?linnarssoniAssemblage Zone. Two species of eodiscoids are present:Neocobboldiaaff.dentataandChelediscus acifer. The latter species is known previously from England and southeastern Newfoundland, and provides a novel link between upper lower Cambrian successions in Baltica and Avalonia.

Morphology, ontogeny and distribution of the Cambrian Series 2 ellipsocephalid trilobiteStrenuaeva spinosafrom Scandinavia

“…1, area 1), northern Lapland (Føyn 1967;Ahlberg 1980;Thelander 1982;Axheimer et al 2007;Cederström et al 2011b); (2) the Laisvall mining district (Fig. 1, area 2), central Lapland (Kautsky 1945;Willdén 1980;Kulling 1982;Ahlberg 1984a;Vidal & Moczydłowska 1996;Moczydłowska et al 2001) and (3) the Lake Storuman area (Fig.…”

“…1, Torneträsk area; 2, Laisvall mining district; 3, Lake Storuman area; 4, Fånån area at Lake Sörsjön; 5, Mjøsa area, SE Norway. Based on Axheimer et al (2007, fig. 1a).…”

“…The biostratigraphy and regional correlation of Cambrian Series 2 of Scandinavia has been reviewed by Ahlberg (1981Ahlberg ( , 1985Ahlberg ( , 1991, Bergström (1981), Ahlberg et al (1986), Moczydłowska (1991), Moczydłowska et al (2001), Ebbestad et al (2003), Nielsen & Schovsbo (2006 and Axheimer et al (2007). Zonation has been commonly based on polymerid trilobites, acritarchs, and in the lowermost part of the section, trace fossils and small shelly fossils.…”

“…Recent studies have revealed important new information on the distribution and stratigraphic significance of trilobites in these successions (e.g. Moczydłowska et al 2001;Ebbestad et al 2003;Axheimer et al 2007;Cederström et al 2009Cederström et al , 2011b. The trilobite faunas include olenelline (holmiid) and ptychopariid (ellipsocephalid) trilobites, together with a few eodiscoids (Moberg 1908;Kiaer 1917;Ahlberg 1980Ahlberg , 1984aAhlberg , 1984bAhlberg & Bergström 1983;Axheimer et al 2007;Cederström et al 2009Cederström et al , 2011b.…”

Biostratigraphical divisions

“…The top of the dentifera-plana Biozone is generally equated with the top of the Ornamentaspis? linnarssoni/"Protolenus" interval, but Axheimer et al (2007, fig. 3) depicted correlation of the latter to be either diachronous or uncertain, rising from the base of the Cephalopyge notabilis Trilobite Zone to the base of the Eoparadoxides harlani Trilobite Zone (Fig.…”