Distribution of subtidal sedimentary bedforms in a macrotidal setting: The Bay of Fundy, Atlantic Canada

• Sedimentary bedforms in the Bay of Fundy were mapped using multibeam sonar.
• Large two-dimensional, flow-transverse dunes occur in fields and linear trains.
• Three-dimensional, flow-transverse dunes occur in sand sheets.
• Horse mussel bioherms are numerous, straights mounds aligned with current flow.
• Banner banks flank prominent headlands and a prominent reef.

The Bay of Fundy, Canada, a large macrotidal embayment with the World's highest recorded tides, was mapped using multibeam sonar systems. High-resolution imagery of seafloor terrain and backscatter strength, combined with geophysical and sampling data, reveal for the first time the morphology, architecture, and spatial relationships of a spectrum of bedforms: (1) flow-transverse bedforms occur as both discrete large two-dimensional dunes and as three-dimensional dunes in sand sheets; (2) flow-parallel bedforms are numerous straight ridges described by others as horse mussel bioherms; (3) sets of banner banks that flank prominent headlands and major shoals. The suite of bedforms developed during the Holocene, as tidal energy increased due to the bay approaching resonance. We consider the evolution of these bedforms, their migration potential and how they may place limitations on future in-stream tidal power development in the Bay of Fundy.