The shelly fauna and biostratigraphy of the lower Cambrian (provisional series 2, stage 4) Evjevik Member, Ringstrand Formation in the Mjøsa area, Norway

Magne Høyberget,Bjørn Funke,Hans Arne Nakrem,Jan Ove Røysi Ebbestad

doi:10.17850/njg95-1-02

Abstract

New, extensive fossil material collected in situ from the lower Cambrian Evjevik Member in the Mjosa type area, southern Norway, allows a reevaluationof the faunal distribution and diversity of the ‘Ornamentaspis’ linnarssoni Zone. Described taxa include three holmiid, six ellipsocephalidand one eodiscoid trilobite in addition to five helcionelloid molluscs. A Holmia species with affinities to the Swedish H. lapponica is common in the Evjevik Member. Librigenae, thoracic segments and pygidia from the poorly known, but biostratigraphically important trilobite ’Ornamentaspis’ linnarssoni (Kiaer, 1917) are documented for the first time. The species is redescribed and transferred to Ellipsocephalus. Helcionelloid molluscs arerepresented by Helcionella antiqua (Kiaer, 1917), Stenotheca norvegica (Resser, 1938), Mackinnonia puppis n. sp., Mackinnonia? sp. and Latouchella sp.These are similar to taxa reported from coeval strata at Gislovshammar in southern Sweden and may prove to have biostratigraphical potential. TheHolmia kjerulfi Zone, the Ellipsocephalus linnarssoni Zone and the Comluella? scanica–Ellipsocephalus lunatus Zone are readily recognised in theLower Allochthon of the Mjosa area and are in this report treated as distinctive, successive zones. New illustrations are provided of the brachiopod Magnicanalis rotundata (Kiaer, 1917), together with the enigmatic fossil Mongolitubulus Missarzhevsky, 1977, recorded for the first time in Norway.

Highlights

The biozonation established for the upper part of the lower Cambrian in Scandinavia is based on the fossili ferous sequences in the Mjøsa area, southern Norway
This zone is recognisable in numer ous outcrops in southern Norway, southern Sweden and Høyberget, M., Ebbestad, J.O.R., Funke, B. & Nakrem, H.A. 2015: The shelly fauna and biostratigraphy of the lower Cambrian Evjevik Member, Ringstrand Formation in the Mjøsa area, Norway
This paper describes the trilobite and helcionelloid mollusc fauna of the ‘O.’ linnarssoni Zone from the type area in Norway, most importantly placing ’O.’ linnarssoni (Kiær, 1917) within Ellipsocephalus

Summary

Introduction

The biozonation established for the upper part of the lower Cambrian in Scandinavia is based on the fossili ferous sequences in the Mjøsa area, southern Norway. 222, 239; Cederström et al, 2012) and one pos sible specimen co-occurring with E. gripi from the grey mudstone of the Gärdsjön Formation in Fånån, Jämtland (Cederström et al, 2009, unfigured), both occurrences interpreted by Nielsen & Schovsbo to be coeval with the lower part of the underlying Tømten Member in the Mjøsa area; suggesting that the distribution of the H. kjerulfi and ‘O.’linnarssoni zonal assemblages reflects biofacies rather than temporal differences. A diverse and abundant fauna of helcionelloid molluscs from this E. linnarssoni-bearing lower part of the Gislöv Formation (Ebbestad et al, 2009) is similar to the pres ently described material from the lower limestone bed in the Evjevik Member. PMO 227.622 is collected from the lower limestone bed

Discussion

Conclusions