A Study of Carbonate Rocks From the Late Visean to Namurian Mabou Group, Cape Breton Island, Nova Scotia
Allen, Tammy L.
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The Late Visean to Namurian Mabou Group of Cape Breton Island conformably overlies the marine to non-marine Windsor Group and unconformably to conformably underlies the fluviatile Cumberland Group. It represents the first non-marine to brackish sediments deposited after the retreat of Windsor seas. Regionally, the Mabou Group comprises two lithologic facies, a grey lacustrine facies and a red fluviatile facies. The grey facies, or lowermost unit, consists predominantly of grey siltstones and shales with interbedded sandstones, and thin carbonates, with gypsum near the base of the section. The grey facies forms the Hastings Formation in the Western Cape Breton Basin, the Cape Dauphin Formation in the Sydney Basin, and the MacKeigan Lake Formation in the Loch Lomond Basin. The upper unit, or the red facies, consists of red with minor green and grey sandstones, siltstones, shales, and minor pedogenic carbonates. Throughout the grey facies of the Mabou Group carbonate rocks occur. Lateral discontinuity of these carbonate rocks does not provide good lithostratigraphic correlations, although their ubiquitous presence in the grey facies of the Mabou Group serves to indicate stratigraphic position. These thin carbonate units consist of various types, ranging from wackestones to grainstones and contain intraclasts, ooids, serpulids, and peloids as constituents. Stromatolitic bindstones comprise the largest percentage of carbonates within the lower unit of the Mabou Group. Carbonate rocks and their associated sediments act as important paleoenvironmental indicators and suggest that deposition of the Mabou Group grey facies occurred within a shallow, subaqueous environment undergoing periods of subaerial exposure. Kwywords: lacustrine, Carboniferous, Mabou Group, stromatolites, ooids, carbonates Pages: 87 Supervisor: Peter Giles