The Lower Cambrian of Scandinavia: Depositional environment, sequence stratigraphy and palaeogeography

• Published in: Earth-science reviews 2011-08, Vol.107 (3), p.207-310
• Main Authors: Nielsen, Arne Thorshøj, Schovsbo, Niels Hemmingsen
• Format: Article
• Language: English
• Subjects: Baltica; Basins; biostratigraphy; chronostratigraphy; Correlation; Deposition; Early Cambrian; Earth science; Floods; Formations; Geography; Marine; Mountains; nomen novum; Northeast; palaeogeography; phosphorite; Regional; Sea level; sea-level changes; sequence stratigraphy; starvation; Stratigraphy; Subsidence; tectonics; transgressive segregation
• ISSN: 0012-8252; 1872-6828
• DOI: 10.1016/j.earscirev.2010.12.004

Lower Cambrian successions described from Scandinavia are reviewed and subjected to sequence stratigraphical analysis; comparisons are also made with successions described from northeast Poland, Estonia, Latvia and Lithuania. The treated stratigraphic interval is bounded upwards by a regional unconformity ascribed to the Hawke Bay Event. The East European regional stage classification, comprising the Rovnian, Lontovan, Dominopolian, Ljubomlian, Vergalian, Rausvian and Kibartian, is adopted for the Lower Cambrian of Scandinavia. These units are approximately equivalent to the Terreneuvian and Cambrian provisional series 2. The Rovnian and Lontovan stages are pre-trilobitic. The Dominopolian and ‘Ljubomlian’ stages encompass the ‘ Rusophycus’ and Schmidtiellus mickwitzi zones; whether the former zone is of pre-trilobitic age is uncertain but possible. The ‘Ljubomlian’ is treated informally because the definition adopted in this paper does not correspond to the original concept of the stage. The Vergalian and Rausvian are for the time being classified as one combined stage. The lower main part of the Vergalian–Rausvian corresponds to the new informal Holmia kjerulfi– ‘Ornamentaspis’ linnarssoni zone, whereas the upper part is separated as the new informal Comluella?–Ellipsocephalus lunatus zone. This zone also includes the Kibartian Stage. Volborthella and poorly known olenellid trilobites range into the Kibartian and the stage is considered of Early Cambrian age. The Holmia inusitata Zone is abandoned; it is contemporaneous with the traditional ‘ O.’ linnarssoni Zone. The autochthonous strata underlying the Hawke Bay unconformity in the Laisvall sector, Swedish Lapland, are assigned to the Laisberg and Grammajukku formations and it is proposed to abandon the Laisvall and Såvvare formations. The Laisberg Fm can locally be divided into the Ackerselet, Saivatj, Maiva, Kautsky Ore, Tjalek, Nadok Ore and Assjatj members. The Vakkejokk Breccia near Luopakte is likely impact related. Sequences are defined as transgressive–regressive depositional cycles bounded by maximum regressive surfaces and their correlative conformities. Sea-level rises are identified by fining-upward lithologies, cratonwards shifts in facies and depocentres, formation of widespread thin lime- and ironstones as well as precipitation of phosphorite and glaucony; the latter formed at remarkably shallow depth in comparison with the modern world. Sea-level falls are identified by coarsening-upward