John R. Dickie

B. Sc. Honours Thesis

Upper Carboniferous Fluvial Sedimentation in the Gulf of St. Lawrence Coal Basin, Mabou Mines, Nova Scotia

(PDF - 5.9 Mb)

Mabou Mines is located on the northwestern coast of Cape Breton Island, Nova Scotia. Steeply dipping sedimentary strata of the Upper Carboniferous Pictou Group (dated as Late Westphalian C) are exposed on the shoreface. These are faulted slivers of coal measures that can be correlated to strata extending far out into the Gulf of St. Lawrence Coal Basin (Hacquebard, in press).

The section contains four major lithosomes; two are shale-dominated and two are sandstone-dominated. Beds within these units were classified on the basis of parameters such as lithology, sedimentary structures, fossil content and colour and subsequently described as lithofacies for analysis.

Shale lithosomes contain abundant shale, coal and black limestone and have been interpreted as flood-plain deposits. The flood-plain was heavily vegetated and studded with shallow lakes. Sandstone lithosomes are interpreted as fluvial channel sandstones on the basis of their lithology and facies associations.

The depositional environment for these strata was a braided river system, not unlike the South Saskatchewan River in Western Canada. Thick vegetative growth on the flood-plain, however, was much greater than in a normal sandy braided river, restricting lateral channel movement. This resulted in an entrenched river that developed vertically-stacked channels through aggradation. As a result, the Carboniferous fluvial system at Mabou Mines developed characteristics usually associated with either braided or meandering systems.

Keywords:
Pages: 129
Supervisor:  Martin Gibling