A Timanian foreland basin setting for the late Neoproterozoic–Early Palaeozoic cover sequences (Dividal Group) of northeastern Baltica

Abstract

LA-ICP-MS U–Pb and Hf-isotope data on detrital zircons from the Ediacaran and Cambrian Dividal Group demonstrate that the autochthonous cover sequence above the Fennoscandian Shield in northernmost Scandinavia is not derived from an easterly Archaean and Palaeoproterozoic source within Baltica as commonly thought. Detrital zircon age populations on four samples from the Dividal Group are dominated by Mesoproterozoic zircons with relatively few Palaeoproterozoic and Archaean zircons. Two samples, from Altevann and Reisadalen have, in addition, a significant population of Ediacaran zircons (c. 570–560 Ma), indicating a Timanian source area for most of the lower Cambrian Dividal Group sediments. The 176Hf/177Hf isotope data show the Ediacaran zircons to be derived from two separate plutonic complexes within the Timanides. It is argued that the Dividal Group sediments were deposited in a foreland basin south and SW of the Timanide Orogen. Similarities with clastic zircon age populations from Cambrian deposits in Akkajaure, Ladoga/White Sea and St Petersburg areas indicate that this foreland basin possibly extended southward for at least 1000 km. A foreland basin setting for the Ediacaran and Cambrian deposits in Central and Southern Scandinavia can thus account for the enigmatic Neoproterozoic detrital zircons in these deposits.Supplementary material:Analytical LA-ICP-MS data on detrital zircons from Dividal Group samples AA12-1, AA12-2, AA11-29 and AA11-30 are available at http://www.geolsoc.org.uk/SUP18731.

New perspectives on the Caledonides of Scandinavia and related areas: introduction

“…These sequences are dominated by the presence of Meso-to Early Neoproterozoic detrital zircon grains, which is taken as evidence for the existence of a 'North-Atlantic branch' of the Grenvillian -Sveconorwegian Orogen in the Neoproterozoic, similar to what has been suggested by Lorenz et al (2012). Andresen et al (2014) studied detrital zircon populations in the Ediacaran -Early Cambrian autochthonous to parautochthonous sedimentary cover in northern Norway. These sequences are dominated by Ediacaran detrital zircon grains, which, rather than being the erosional product of their own basement, indicate that these rocks represent foreland deposits of the contemporaneous Timanian orogen.…”

Detrital zircon signatures of the Baltoscandian margin along the Arctic Circle Caledonides in Sweden: The Sveconorwegian connection

“…7). Data from the underlying autochthonous sandstones of the Dividal Group (Andresen et al, 2014) likewise are dominated by the same Mesoproterozoic to late Paleoproterozoic populations, despite the lack of rock units of these ages in the underlying basement. Notably, these autochthonous strata also include a strong Timanian (c. 550-650 Ma) signature.…”

Middle to Late Devonian–Carboniferous collapse basins on the Finnmark Platform and in the southwesternmost Nordkapp basin, SW Barents Sea

“…These Greenstone belts formed as NW-SE-trending rift basins in the Paleoproterozoic during the opening of the Kola Ocean Torske, 1986, 1988), although more recent studies tentatively reinterpret these rocks as foreland basin deposits derived from the Svecokarelian Orogeny (Torske and Bergh, 2004). A thin cover of Neoproterozoic to Cambrian (para-)autochthonous metasedimentary rocks occurs on top of Paleoproterozoic basement rocks in Finnmark (Siedlecki, 1980;Ramsay et al, 1985;Andresen et al, 2014;Corfu et al, 2014). Other Neoproterozoic-Ordovician units in eastern Finnmark include metasedimentary rocks of the Barents Sea and Tanafjorden-Varangerfjorden regions (Siedlecki, 1980;Siedlecka and Roberts, 1992), which are exposed on the Varanger Peninsula (Fig.…”