SEDIMENTOLOGY OF THE LOWER SPRINGHILL MINES FORMATION, CUMBERLAND BASIN, NOVA SCOTIA

The Pennsylvanian (Langsettian-Duckmantian) Springhill Mines Formation is a 660 m thick, coal-bearing unit deposited in the Cumberland Basin of mainland Nova Scotia. Although this formation represents the uppermost part of the world-famous Joggins “section,” this study is the first detailed sedimentological examination of the lower 180 m of this unit.

The basal 10 m consists of interbedded dark gray shale and fine-grained, wave-rippled, sheet sandstones. This interval records flooding of the basin and deposition in a standing body of water deep enough to inhibit plant growth. The overlying 170 m consists of seven alternations between poorly-drained and well-drained floodplain facies. Poorly-drained floodplain deposits (8-22 m thick) include green and gray mudstones, thin coal beds, channel bodies, and sheet sandstones with entombed lycopsids and calamites. These facies were deposited in forested, clastic and peat-forming wetlands. Well-drained floodplain deposits (14-25 m thick) consist of red mudstones and sheet sandstones. Roots and scattered green mottles are present throughout well-drained intervals. Well-drained facies are interpreted to represent deposition on a seasonally-oxidizing floodplain.

The facies and stratigraphic architecture of the lower Springhill Mines Formation is remarkably similar to that of the underlying Joggins Formation. This similarity suggests that alternations between poorly-drained and well-drained facies record sea-level fluctuations in a tectonically active basin.