Precambrian–Cambrian boundary interval deposition and the marginal platform of the Avalon microcontinent

摘要: Abstract Thick terminal Proterozoic–lowest Cambrian successions allow reference of the Saint John, New Brunswick, and MacCodrum Brook, southern Cape Breton Island, areas to marginal platform Avalon microcontinent. Marginal-platform siliciclastic-dominated sequences form a cover on Late Precambrian arc from Brunswick North Wales. Their deposition in fault-bounded basins began with origin microcontinent development persistent transtensional regime latest Precambrian. The Avalonian consists three successive lithofacies associations: lower subaerial rift marginal-marine facies; overlying cool-water, wave-influenced, marine sandstones shales; higher macrotidal quartz arenites (=Avalonian depositional 1–2). Only Lower onlap southeast, where they oldest unit inner platform. These major are Rencontre, Chapel Random formations, respectively, America. Southwest thinning Rencontre–Chapel Island–Random interval reflects slower subsidence area city John. sequence 1–2 unconformity, which falls sub-trilobitic Watsonella crosbyi Zone Island Formation, persists for 650 km along southeastern Newfoundland and, potentially, appears Island. Latest Precambrian-earliest epeirogenic history was very uniform platform, unified lithostratigraphic nomenclature is appropriate.