Tidal signatures in a shelf-margin delta
Tidal signatures in a shelf-margin delta
Geology (Boulder) (April 2006) 34 (4): 249-252
- Atlantic Ocean
- basins
- bottom features
- Canada
- clastic rocks
- coastal environment
- continental margin sedimentation
- continental shelf
- continental slope
- Cretaceous
- deltaic environment
- depositional environment
- Eastern Canada
- geophysical methods
- geophysical surveys
- inner slope
- intertidal environment
- lithofacies
- Lower Cretaceous
- Maritime Provinces
- Mesozoic
- Missisauga Formation
- mudstone
- North Atlantic
- Northwest Atlantic
- Nova Scotia
- offshore
- oil and gas fields
- outer shelf
- paleo-oceanography
- petroleum
- progradation
- sandstone
- sea-level changes
- sedimentary basins
- sedimentary rocks
- sedimentation
- seismic methods
- sequence stratigraphy
- surveys
- terrigenous materials
- tidal currents
- Sable Subbasin
- Glenelg Field
Based on its anomalous thickness ( approximately 150 m) and stratigraphic position above continental-slope mudstone, an upward-coarsening succession consisting in part of tidal rhythmites in the Glenelg Field, offshore Nova Scotia, Canada, is interpreted to be a strongly tide-influenced shelf-margin-delta deposit. A large, funnel-shaped erosional shelf-edge invagination is observed where the paleoshelf edge is resolved in three-dimensional seismic data adjacent to Glenelg. We propose that the delta at Glenelg prograded into a similar shelf-edge invagination within which tidal currents were amplified and wave energy was attenuated. Given that funnel-shaped invaginations (e.g., slope canyon heads, slump scars, fluvially incised knickmarks) are relatively common along modern shelf edges, and that fluvio-deltaic systems should be focused into these topographic lows during regression across the shelf, it seems likely that shelf-edge invaginations play an important but underappreciated role in mediating terrigenous clastic sedimentation during sea-level lowstands.
