THE SPRINGHILL MINES FORMATION, CUMBERLAND BASIN, NOVA SCOTIA: EVOLUTION OF CHANNEL BODY ARCHITECTURE WITHIN A PENNSYLVANIAN FLUVIAL SYSTEM

The Pennsylvanian Springhill Mines Formation has been previously interpreted to represent the deposits of an ancient anastomosed river system. Reexamination of the channel bodies within this unit reveals more complexity and variety than previously recognized.

Channel bodies are grouped into three distinct morphologies. Fixed channel bodies tend to be single story and exhibit a simple cut and fill architecture. These channel bodies are composed of fine to medium grained sandstone organized into trough cross-beds and ripple cross-laminae; muddy abandonment fills are present locally. Sheet-like channel bodies exhibit a more complex architecture dominated by low angle, cross cutting erosional surfaces. These channel bodies are composed of fine to medium grained sandstone with trough cross-beds and ripple cross-laminae. Laterally-accreting channel bodies exhibit a single story architecture, dominated by lateral accretion surfaces. The lower portion of these bodies consist of trough cross-bedded sandstone that passes upwards into inclined heterolithic packages of mudstone and ripple cross-laminated sandstone.

Channel bodies within the Springhill Mines Formation increase in thickness and abundance near the top of the formation. Overall these channel bodies record a southeasterly paleoflow direction, which does not systematically vary with size, morphology or stratagraphic position. Large meandering channel bodies dominate the top and bottom of the section; resembling those within underlying and overlying formations. Fixed and sheet-like channel bodies are found in the middle of the formation; dominated by red beds. Systematic changes in architecture may reflect long term changes in climate or geomorphic position on the floodplain.