Type Locality:

Polly Brook, near River Philip, Cumberland County, Nova Scotia (NTS 11 E/12). The type section extends along Polly Brook from Smith's Pond on the Rodney Road, downstream (northeast) for about 3 km. The formation also outcrops along Polly Brook downstream to about 550 m from the junction with the River Philip.

Distribution:

The Polly Brook is best developed in the south-central parts of the Cumberland Basin near the Cobequid Highlands, but appears to be absent in the eastern part of the Tatamagouche Syncline and in the Joggins section. Although not fully exposed in the type area, the Polly Brook is estimated to be 1400 m thick (Ryan et al., 1991). In the Springhill area, the formation is about 600 m thick (Calder, 1985) and rapidly thins to the east, west and north.

Lithology:

The formation is an intermediate-marginal, polymictic conglomerate; the ortho- and paraconglomerates range from pebble to boulder size and are moderately to poorly rounded and sorted. The clasts are commonly rhyolite, granite, diorite and metamorphic rocks derived from the Cobequid Highlands Massif. Older Carboniferous sedimentary clasts, especially from the Boss Point Formation, are locally common and help to distinguish the Polly Brook from the Claremont Formation, which has predominantly igneous and metamorphic clasts. Intercalated with the conglomerates towards the top of the formation, are 5-10 m thick, pebbly, immature, cross-stratified sandstones. There are rare mudstones. In the type area of the Springhill Mines Formation, the uppermost strata of the Polly Brook are finer grained with thinly interstratified, poorly sorted, granule conglomerate and silty mudrock. The Polly Brook Formation represents primarily debris flow deposits.

Relationship:

The Polly Brook Formation is one of eight formations of the Cumberland Group (Davies et al., 2005); these are, in approximate ascending order: the Claremont, the Boss Point, the Little River, the Joggins, the Springhill Mines, the Polly Brook (which is collectively equivalent to the Little River, the Joggins and the Springhill Mines), the Ragged Reef, and the Malagash formations. The lower boundary with the underlying Boss Point Formation is rarely exposed. From an outcrop along Black River, near Deep Brook, Bell (1938a, 1944b) interpreted rocks now included in the Polly Brook as unconformably overlying the Boss Point. But faulting complicates the relationship. The Polly Brook is transitional to disconformable with the Boss Point in the River Philip area; there is an angular discordance in the Donaldson's Mill Brook area. In the western part of the Cumberland Basin, the Polly Brook Formation nonconformably overlies basement rocks of the Cobequid Highlands Massif. Ryan et al. (1991) regarded the Polly Brook as being laterally equivalent to, and probably interfingering with, the Joggins Formation and the lower beds of the Springhill Mines Formation (Calder, 1984).

History:

Strata now included in the Polly Brook Formation were previously mapped as the "Lower Coarse Facies" of the Cumberland Group (Shaw, 1951; Copeland, 1959; Calder, 1984; Ryan, 1986; Ryan et al., 1987.

Other Citations:

Bell 1938a, 1944b; Calder, 1984, 1985; Copeland, 1959; Davies et al., 2005; Dolby, 1988; Ryan, 1986; Ryan et al., 1987, 1991.

References:

Bell, W.A., 1944b. Carboniferous rocks and fossil floras of northern Nova Scotia; Geological Survey of Canada, Memoir 238, 277 p.

Calder, J.H. 1985: Depositional environment of the Westphalian B, Cumberland Basin coals of Springhill, Nova Scotia. In: Report of Activities, Mines and Minerals Branch, 1984. Edited by K.A. Mills and J.L. Bates. Nova Scotia Department of Mines and Energy, Report 85-1, pp.11-12.

Calder, J.H., 1984. Sedimentology studies within the Springhill coalfield, Cumberland County, Nova Scotia, pp. 1-6: in J. Szostak and K.A. Mills (eds.), Report of Activities, 1983; Nova Scotia Depart-ment of Mines and Energy, Mineral Development Division, Report 84-1, 341 p.

Copeland, M.J., 1959. "Coalfields, west half Cumberland County, Nova Scotia"; Geological Survey of Canada, Memoir 298, 89 p.

Davies, S.J., Gibling, M.R., Rygel, M.C., Calder, J.H. and Skilliter, D.M., 2005. The Pennsylvanian Joggins Formation of Nova Scotia: sedimentological log and stratigraphic framework of the historic fossil cliffs; Atlantic Geology, vol. 41, pp. 115-142.

Dolby, G. 1988: Palynological analysis (of) samples from the Cumberland Basin and Cape Breton Island, Nova Scotia.; Part II. Unpublished report prepared for the Nova Scotia Department of Mines and Energy, 34 p.

Ryan, R.J. 1986: Geology of the Tatamagouche Syncline, Cumberland Basin, Nova Scotia. Geological Survey of Canada, Open File 1257, 56p.

Ryan, R.J., Boehner, R.C. and Calder, J.H. 1991. Lithostratigraphic revisions of the upper Carboniferous to lower Permian strata in the Cumberland Basin, Nova Scotia and the regional implications for the Maritimes Basin in Atlantic Canada; Bulletin of Canadian Petroleum Geology, vol. 39, No. 4, pages 289-314.

Ryan, R.J., Calder, J.H., Donohoe, H.V. Jr and Naylor, R. 1987: Sedimentation and basin evolution adjacent to the Cobequid Highlands Massif, eastern Canada. In: Basins and Basin Forming Mechanisms. Edited by C. Beaumont and A. Tankard. Canadian Society of Petroleum Geologists, Memoir 12, pp. 311-317.