Significance of a late neoproterozoic – Early Cambrian southern Baltica active margin in late-stage Rodinian and early Gondwanan reconstructions

Abstract

New whole-rock geochemical data indicate changing provenance of sedimentary rocks deposited on the southern margin of Baltica in the late Neoproterozoic to early Paleozoic. The oldest part of the sequence is characterized by highly weathered detritus sourced from a mafic igneous source, inferred to be the nearby Volyn Large Igneous Province (L.I.P.), in an intracontinental rift (aulacogen) setting. Neoproterozoic–Cambrian boundary sequences are weakly weathered and sourced from intermediate to felsic rocks in an active margin setting whereas the youngest parts of the sequence exhibit significant quartz accumulation consistent with deposition of recycled material in a passive margin setting. These data support published U-Pb and Lu-Hf zircon data from the same sedimentary sequence where the Neoproterozoic-Cambrian boundary strata are characterized by anomalously high Ediacaran–Cambrian zircon contribution with juvenile isotopic composition. Taken together, these data indicate a cryptic late Neoproterozoic–early Cambrian active margin along the periphery of southern Baltica. Based on a correlation of similarly aged foreland basin and accretionary complexes, and links to paleomagnetically constrained plate reconstructions it is hypothesized that this detritus was sourced from the Avalonian micro-continent and a Cambrian arc terrane that is today preserved in high-grade metamorphic complexes of the European Variscides. These findings have potentially profound implications for our understanding of the supercontinent cycle that links the Rodinia to Pangea supercontinents, in particular the role played by Baltica-derived terranes in Paleozoic collisional orogeny.