Abstract

The identification of a late Archean arc–trench assemblage in northwestern Ontario provides the opportunity to compare depositional systems developed in a Precambrian convergent setting with Cenozoic examples. Two types of sedimentary associations exist in the accretionary complex. Medium- to thick-bedded Bouma A, AB, and ABC felsic turbidites dominate the belt. These are primarily organized into unstructured sequences and reflect deposition in a ramp-like environment with multiple feed points supplying sediment from a forearc basin. Mafic turbidites with possible shallow water reworked intervals form isolated pods within the metasedimentary belt. Erosion of upthrust blocks of sedimentary strata containing ultramafic masses supplied this sediment to elevated slope basins. These types of depositional systems are similar in many respects to those developed in Cenozoic and Holocene arc–trench settings.

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