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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.

The development of fast and reliable instrumental methods for U-Pb dating and Lu-Hf isotope analysis of zircon has caused detrital zircon to become a popular provenance indicator for clastic sediments and an important tool in basin analysis. In parallel with the increasing ease of access to data, advanced methods of data interpretation have been developed. The downside of some techniques for visualization and comparison of detrital zircon distribution patterns is that the results are difficult to relate to what the zircon grains really record: The age and nature of geological processes in a protosource terrane. Some simple methods of data presentation and inter-sample comparison that preserve a direct and intuitively understandable relationship between the data and the age of zirconforming processes in the protosource are proposed here: Comparison of confidence intervals around empirical, cumulative distribution curves combined with the use of a plot of upper vs. lower quartile values of cumulative zircon U-Pb age or Lu-Hf model age distributions. This approach allows a robust and transparent separation to be made between samples whose detrital zircon distributions are indistinguishable from each other, and those that are more or less similar. Furthermore, it allows simple comparison between detrital zircon distributions and the geological age record of potential protosource terranes, or the detrital zircon distributions of possible sedimentary precursors.

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U–Pb and Lu–Hf isotope analyses of detrital zircon from the latest Ordovician (Hirnantian) Langøyene Formation, the Late Silurian Ringerike Group and the Late Carboniferous Asker Group in the Oslo Rift were obtained by laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS). Overall the U–Pb dating yielded ages within the range 2861–313 Ma. The U–Pb age and Lu–Hf isotopic signatures correspond to virtually all known events of crustal evolution in Fennoscandia, as well as synorogenic intrusions from the Norwegian Caledonides. Such temporally and geographically diverse source areas likely reflect multiple episodes of sediment recycling in Fennoscandia, and highlights the intrinsic problem of using zircon as a tracer-mineral in ‘source to sink’ sedimentary provenance studies. In addition to its mostly Fennoscandia-derived detritus, the Asker Group also have zircon grains of Late Devonian – Late Carboniferous age. Since no rocks of these ages are known in Fennoscandia, these zircons are inferred to be derived from the Variscan Orogen of central Europe.