Abstract

The Lower Carboniferous Bonaventure Formation of western Chaleur Bay, Gaspé and New Brunswick, is a terrestrial redbed succession with abundant calcretes, deposited in a semi-arid paleoclimate. Facies can be grouped into three associations, conglomeratic, sandstone, and mud-dominated, within two 100–150 m upward-fining megasequences. The megasequences are attributed to alluvial fan progradation due to tectonic rejuvenation.Vertical facies relationships and internal structures indicate that varied alluvial environments are represented. Alluvial fans formed on steep slopes adjacent to fault scarps and are dominated by deposits of the conglomeratic association. Lateral and downslope coalescence of fans into a braid plain is represented by transition from the conglomeratic to the sandstone facies association. Distally, the braid plain is transitional into deposits of the mud-dominated association.Paleocurrents and clast compositions show that sediment in the Gaspé outcrops was derived from the northwest, and that in New Brunswick from the southwest. This indicates that Chaleur Bay is an exhumed Carboniferous paleovalley, with axial drainage to the east.

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