BASIN-MARGIN FACIES OF THE PENNSYLVANIAN RAGGED REEF FORMATION, CUMBERLAND BASIN, NOVA SCOTIA

Proximal facies of the Ragged Reef Formation (Pennsylvanian; Duckmatian-Bolsovian) crop out along the southern shore of Chignecto Bay in the Cumberland Basin of Nova Scotia between Spicers Cove and Sand River. Basin-margin facies at Spicers Cove consist of matrix-supported alluvial fan deposits that pass laterally into muddy floodplain deposits with sheet sandstones, thin coals, and drab-colored mudrocks. At West Beach (2.5 km from the basin margin), 2 to 43-m-thick, multistorey sandstone channel bodies make up ~60% of the thickness of the section. These bodies are organized into stacked sets of trough cross-beds capped by horizontal- and ripple cross-laminae. Floodplain deposits (0.2 to 9.4 m thick) are composed of sheet sandstones and red to drab mudrocks with carbonized roots, Stigmaria, in situ lycopsids, and transported calamite and fern fragments. Exposures between Edgetts Beach and Birch Cove (~9 km from the basin margin), are composed of conglomeratic channel bodies (up to 34 m thick; ~50% of section thickness) and drab-colored floodplain deposits. Channel bodies are composed of >50% clast-supported, pebble to cobble conglomerate with crude horizontal stratification, imbricated clasts, and cross-beds up to 2.2 m thick. Floodplain deposits range from 0.2 to 5.1 m thick and are dominated by drab mudrocks and sheet sandstones.

Exposures at Sand River (~11 km from the basin margin) consist of multistorey channel bodies up to 17 m thick (~69% of section thickness) composed of pebbly sandstone organized into trough cross-beds capped by horizontal- and ripple cross-laminae. Overbank deposits (~30% of section thickness) consist of sheet sandstone and red mudrocks with scatted carbonized roots and are similar to those in the type section of the Ragged Reef Formation.

This transect records the transition from basin-margin alluvial fans and peat-forming wetlands at Spicers Cove, to conglomeratic fluvial systems and floodplain wetlands between West Beach and Birch Cove, to redbeds and sandstone channel bodies at Sand River. In addition to changes in drainage and fluvial style, these sections record a progressive shift from a local source area in the Cobequid Highlands of Nova Scotia to a more extensive, through-going drainage system sourced in the Caledonia Highlands of New Brunswick or beyond.