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Abstract

The 2.3 km thick Lower Devonian Battery Point Formation conformably overlies shallow marine sandstones of the York River Formation and coarsens upward into proximal braidplain deposits of the Malbaie Formation. Whereas the lower part consists largely of west to northwesterlydraining distal sandy braidplain and meandering fluvial systems, the uppermost Fort Prevel Member (760 m thick) contains a variety of fluvial deposits formed in direct (tectonic) and indirect (climatic) response to early Acadian deformation.

Four lithofacies associations are recognized in the Fort Prevel Member. The lowest (Association 1, 80 m thick) consists of isolated and amalgamated sheet sandstones with parallel lamination and trough crossbedding deposited in low sinuosity, north to northeastwardflowing, sandbed fluvial channels.

Association 2 (235 m thick) largely comprises laterally and vertically variable thin channelfill and sheetflood sandstones deposited on extensively desiccated ephemeral mudflats. In the lower part, these sediments interbed with mainly parallellaminated, amalgamated sheet sandstones, with crosscutting channel fills flowing toward the north and northeast. At the top of the association, axial ESEflowing, more perennial fluvial systems traversed ephemeral mudflats.

Association 3 (165 m) consists of stacked planar and trough crossbedded sandstones deposited in major ESEflowing axial drainage systems, overstepped by more proximal, though still axially flowing, sandy braidplain facies of Association 4 (260 m thick).

A tectonic model is proposed for the reversal in dispersion direction of axial drainage systems in the Battery Point Formation, incorporating recent views on the Acadian Orogeny as involving oblique continental collision of several microcontinents. Collision with the St. Lawrence promontory initiated subsidence in the Gaspe Basin and supplied longitudinal fluvial systems flowing westward into a coastal embayment during lower Battery Point Formation time. Later collision of the New York promotory to the southeast reversed basin axis slope during deposition of the Fort Prevel Member. This supplied sediment longitudinally eastward and southeastward into an uplifted, probably enclosed semiarid basin. Marginal basin uplift to the south later generated the Malbaie Formation conglomerates.

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