A paradoxidid–agnostoid fauna from the mid-Cambrian (Stage 5) of the Caledonian Lower Allochthon on Tåsjöberget, Ångermanland, Sweden

Abstract

We describe faunas, formerly very little known, from allochthonous mid-Cambrian strata in the Fjällbränna Formation (Tåsjön Group) in Ångermanland that are equivalent to the “Paradoxides oelandicus Beds” of the autochthon. Paradoxidid trilobites are by far the commonest forms but are represented only by dissociated sclerites; 7–10 taxa appear to be present, but most of them are so incomplete that they cannot be identified with certainty. They are accompanied by rare agnostoids of two taxa, Pentagnostus praecurrens and Acadagnostus acadicus. The assemblages lack eodiscoid or other polymerid trilobites, molluscs and brachiopods, and in this respect contrast with shallower-water shelf faunas in the “Oelandicus Beds” of the Swedish autochthon, but bear comparison with shelf-edge or slope faunas from Novaya Zemlya (Arctic Russia), the Moesian Platform (Romania) and South Carolina (USA).

Keywords::

• Trilobites
• Acadoparadoxides (Baltoparadoxides) oelandicus Superzone
• Lower Allochthon
• Caledonides
• Sweden

Acknowledgements

The authors thank Linda Wickstrom (Swedish Geological Survey, Uppsala), for enabling a loan of the type specimen of P. torelli and Dr Vivianne Berg-Madsen (Museum of Evolution, Uppsala) for assistance with the literature. Most of the photography was accomplished by Phil Crabb and Phil Hurst (Natural History Museum, London). The authors thank Prof. David L. Bruton (The Natural History Museum at the University of Oslo) and Prof. Per Ahlberg (Department of Geology, Lund) for helpful reviews of the manuscript.