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

Abstract

AbstractLA-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.