BIOTIC-SEDIMENT INTERACTIONS IN A SEQUENCE STRATIGRAPHIC FRAMEWORK: THE LATE CARBONIFEROUS SYDNEY MINES FORMATION AT MORIEN BAY, NOVA SCOTIA

Coastal exposures of the Sydney Mines Formation (Westphalian D) at Morien Bay provide a detailed perspective on the paleoecology of a Carboniferous wetland environment. The strata consist of fluvial, restricted marine, and possibly lacustrine strata, with economic coals. Measured 75-150m sections at Schooner Pond, Long Beach and Port Morien include the Emery to Harbour seam interval. Stacked high-frequency sequences, 10-30m thick, are bounded by mature paleosols (calcretes, vertisols), with maximum flooding defined by thick coal and faunal (bivalve)-concentrate limestone/shale. Grey, wetland facies are well represented in the Transgressive and Highstand Systems Tracts, and red/grey dryland facies in the topmost Highstand to Lowstand Systems Tracts.

Forested horizons of calamitacean and lepidodendrid trees standing in their growth position are observed at many levels, with large stigmarian rooting systems. Most horizons were found in grey siltstone and sandstones with small distributary-type channels, implying poorly drained or wetland associations within the Transgressive and Highstand Systems Tracts. Abundant compression flora of Neuropteris, Alethopteris, Pecopteris, and Cordaites sp. are recorded throughout all sections, mainly in wetland facies but also as rarer litter identified in red beds of the Highstand through Lowstand Systems Tracts.

A well-preserved tetrapod trackway was discovered at Long Beach, just below the Phalen Seam. Preserved tracks are rare in the Sydney Basin and have not been significantly studied. Located within a shallow gully in a multi-story dryland channel body deposit (Lowstand Systems Tract), this ~3m long trackway preserves 18 footprints generated in a soft, wet substrate. Ripple marks indicate that the direction of travel was downflow, and dryland conditions are suggested by rainprints, rill marks, and windblown sand. A smaller set of tetrapod trackways was found higher in the section as well as two separate Arthropleura trackways.