COARSE-GRAINED MEANDERING FLUVIAL SYSTEMS OF THE PENNSYLVANIAN RAGGED REEF FORMATION, CUMBERLAND BASIN, NOVA SCOTIA

The type section of the Pennsylvanian Ragged Reef Formation (Duckmantian) crops out along the shore of the Bay of Fundy in the Cumberland Basin of Nova Scotia. The 864-m-thick type section consists of 47 channel bodies (57%) separated by red (42%) and drab (2%) floodplain deposits. Channel bodies range from 1.9 m to 21.5 m thick and appear to be broad sheets with minimum width:thickness ratios >50. Most channel bodies record southeasterly paleoflow, suggesting a source area in the Caledonia Highlands of New Brunswick and/or the more distant Appalachian Orogen. Channel bodies are composed of multiple stories that range from 1-11 m thick. Storey boundaries are marked by significant erosional relief and are lined with pebbly lags. Internally, many stories have pronounced lateral accretion surfaces with abundant trough cross-beds, and are capped with horizontal- and ripple-cross laminae. Average grain size ranges from fine-grained sandstone to pebbly, coarse-grained sandstone and broadly increases upwards through the formation. Beds of cross-bedded, matrix-supported, pebble conglomerate (max. clast size = 9 cm) become abundant above 727 m.

Overall, the type section of the Ragged Reef Formation is interpreted to represent a meandering fluvial system that transported sand and gravel across a seasonally oxidizing floodplain. A coarsening-upwards trend within the formation records the progradation of proximal facies from the Caledonia Highlands into the center of the western Cumberland Basin. Although overbank deposits are predominantly composed of redbeds deposited in a seasonally-oxidizing floodplain, they lack well-developed paleosols, calcareous horizons, and other obvious paleoclimate indicators.