New evidence for the Baltican cratonic affinity and Tonian to Ediacaran tectonic evolution of West Avalonia in the Avalon Peninsula, Newfoundland, Canada

Abstract

Provenance studies of quartzite clasts and enclosing sandstone units in the Avalon Peninsula, Newfoundland, Canada, were conducted to test the Baltican or Gondwanan cratonic affinities of West Avalonia and examine the stratigraphic archives of Neoproterozoic arc evolution. Four cobble-sized quartzite clasts from a syn-orogenic, Ediacaran fluvial unit mostly yield ca. 1220, 1510, and 1900–2200 Ma detrital zircon age maxima and were probably derived from sub-arc basement units. Detrital zircon U-Pb-Hf isotope statistical assessments of the clasts indicate provenance ties with Proterozoic strata of the Sarmatian craton and Timanian passive margin of northern Fennoscandia, which corroborates models for proto-Avalonia to have originated near southern or northeastern Baltica, respectively. Analogous quartzite basement units in Nova Scotia and New England also have Baltican cratonic affinities and reflect provenance from southern Fennoscandia. Ediacaran exhumation of arc and basement infrastructure was accommodated by transpressive faults during the Avalonian orogeny and resulted in the deposition of Signal Hill Group terrestrial strata. Eleven Signal Hill Group sandstone samples are correspondingly dominated by Tonian to Ediacaran detrital zircon age fractions that constrain the crustal evolution of West Avalonia. The composite dataset includes 818–777 Ma detrital zircon grains that record the rifting of a proto-Avalonia sliver or ribbon arc from Baltica. Tonian igneous rocks are rare in West Avalonia, but ca. 760 Ma and 730 Ma detrital zircon grains indicate both crust and mantle contributions to the oceanic Burin arc, its tectonic interactions with proto-Avalonia, and subsequent arc magmatism across the composite terrane. Cryogenian detrital zircon ages substantiate the timing of 700–670 Ma magmatism and 670–640 Ma tectonic interactions with Baltica or another block. The detrital zircon U-Pb-Hf isotope record of the 640–600 Ma magmatic phase includes 6–9 Myr-long, fluctuating cycles that indicate the frequency of West Avalonian arc processes in the Mirovoi Ocean prior to Avalonian orogenesis.