EVOLUTION OF MESOPROTEROZOIC BASINS IN ARCTIC CANADA DURING RODINIA ASSEMBLY (Invited Presentation)

The stratigraphic architecture of the late Mesoproterozoic Borden Basin on northern Baffin Island (Arctic Canada) exhibits sag, rift, and foreland-basin–like phases. Although the succession starts with flood basalt indirectly attributed to the ~1270 Ma Mackenzie LIP, geochronological data indicate that deposition of most of the Bylot Supergroup took place ca. 1100–1050 Ma. The thin, partly subaqueous basal basalt is overlain by mature shallow-marine quartz arenite, upward-deepening siltstone and shale marking the beginning of rifting, a complex suite of rift-controlled carbonate units containing two dramatic internal unconformities and evidence of unusual basinal environments, and an uppermost flysch-molasse–like siliciclastic succession. Detrital zircon geochronology indicates that material derived from the Grenville orogen was first delivered after deposition of the unusual carbonates, of which some exhibit evidence of lacustrine deposition and alternating compressional and extensional stress regimes. Given the temporal constraints on deposition of the Bylot Supergroup and the idiosyncratic architecture of the basin-fill, the rift cannot be interpreted as an aulacogen as in previous work. Its detailed characteristics are instead more compatible with a rift system that developed in response to far-field stress caused by continent–continent collision (a type of rift known as an impactogen) during Rodinia’s assembly.