The late Cambrian (Furongian) Acerocarina Superzone (new name) on Kinnekulle, Västergötland, Sweden

Abstract

The traditional Furongian biozones of Scandinavia, based on olenid trilobites, are proposed elevated to superzonal rank. For the time being they are treated informally, except that the designation Acerocarina Superzone is proposed as replacement name for the uppermost superzone, formerly referred to as the Acerocare Zone. It comprises four zones. The lowest of these zones, hitherto referred to as the Peltura transiens Zone, is renamed as the Acerocarina granulata Zone. The distribution of the Acerocarina Superzone in Baltoscandia is mapped. A newly discovered 1.4 m thick succession on Kinnekulle, Västergötland, yielded Parabolina heres heres, P. transiens, Peltura costata, Peltura scarabaeoides westergaardi and Sphaerophthalmus alatus. In addition, A. granulata, Pelturina punctifera and Leptoplastides? sp. were collected from loose boulders deriving from the same interval. This is the first unambiguous record of P. costata and P. punctifera in Sweden. The fossil assemblage, assigned to the P. costata Zone, contains species hitherto considered characteristic of five different biozones, viz. the Ctenopyge tumida Zone, the Parabolina lobata Zone, the P. transiens Zone, the P. costata Zone and the Westergaardia scanica Zone. P. transiens, P. scarabaeoides westergaardi and S. alatus are assumed to have been reworked, whereas P. punctifera appears one zone earlier than in Norway. Parabolina (Parabolina) heres lata, not found during this study, may turn up in the P. costata Zone or even earlier. The Acerocarina Superzone is resting on the P. lobata Zone, and the intervening zone, characterized by Peltura paradoxa (uppermost “Peltura scarabaeoides” superzone), is missing in the succession on Kinnekulle.

Keywords:

• Trilobites
• biostratigraphy
• Acerocarina Superzone
• Furongian
• Sweden

Acknowledgements

We thank A. Buchholz, Stralsund, and M. Høyberget, Mandal, for discussion on the co-occurrence of trilobites in the “P. scarabaeoides”–Acerocarina superzone boundary interval as well as taxonomic issues. F. Rudolph, Wankendorf, kindly directed our attention to the in situ occurrence of the P. costata Zone in the Trolmen Quarry. Fredrik Terfelt is acknowledged for discussions on reworking of trilobites in the Alum Shale. Reviewers Fredrik Terfelt and Per Ahlberg, Lund, are thanked for constructive comments that improved the original manuscript.