Garth A. Prime

Late paleozoic deposition in Maritime Canada primarily occurred in the Fundy Basin, a large trough system which is thought to have formed within a transcurrent fault zone. It consisted of a series of interconnected subbasins and uplifted basement blocks, with remnants of the basins existing today as thick Devono-Carboniferous cover. The Antigonish Basin is one of these remnants. A sedimentological study of its rocks provides insight into its sedimentary tectonic history.

The development of the Antigonish Basin occurred in two stages: (1) an initial stage of tectonic activity, and (2) a final stage of tectonic quiescence. Tectonic activity extended from the Middle-Late Devonian to the Tournaisian, during which time there were at least two major episodes of uplift of the Browns Mountain Massif. A large alluvial-fan system shed extensive deposits to the northeast while a transverse fluvial system occupied more distal regions. The Visean marked the beginning of tectonic quiescence, a period during which local topography was subdued with source areas generally located well beyond the basin margins. A marine invasion of the basin in the Visean repeatedly inundated a coastal floodplain. Marine influences ended in the Namurian with the appearance of an extensive lake system. In Early Westphalian time the lake system was replaced by successive major river systems with distant source areas. Deposition apparently ceased after this time.

The initial tectonic activity in the basin can be traced to movement along two major splaying strike-slip faults, the Chedabucto and Hollow Faults, which enclosed the Antigonish Basin and Browns Mountain Massif. When these dextral faults were concurrently active, a region of compression and uplift developed where they converged. Correspondingly, extension and subsidence occurred where they diverged. This setting produced a major source area which supplied relatively constant detritus to the adjacent fault-wedge basin. When concurrent movement along the faults declined in the Visean, local tectonism became reduced as well. Consequently all subsequent deposition was influenced by more regional tectonic mechanisms and regional sediment dispersal patterns.

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Pages: 240
Supervisor: Paul E. Schenk