Geologic characterization of Northeast Atlantic Submarine Canyons and Seamounts using observations from the NOAA Deep Connections 2019 Expedition

The Deep Connections 2019 expedition (EX1905L1 and EX1905L2) aboard the NOAA Ship Okeanos Explorer sought to fill knowledge gaps regarding submarine canyons and seamounts in the area between Halifax, Nova Scotia to the north and Newport, Rhode Island to the south. Deep Connections mapped 19,000 km2 of seafloor to date using high resolution multibeam sonar and acquired video and sample observations from numerous unexplored submarine canyons. These new data augment our understanding of geologic processes occurring in Northeast Atlantic submarine canyons, which have recently been found to be more geologically active during sea level highstands than conceptualized during early investigations.

Seafloor mapping conducted during leg 1 of Deep Connections 2019 show ample evidence of recent geologic activity within submarine canyons, including axial channel incision, high reflectivity/rugosity “fresh” debris fields downslope of canyon walls, and occasionally sediment ripples. A small subset of the general area of interest has been surveyed by NOAA three times using high resolution multibeam: prior to 2009, 2013, and 2019. The difference in depth between these surveys identify recent slope failures and potential post-failure modification of large landslide scars. ROV dives during Deep Connections 2019 provided ground truth evidence of recent geological activity, including slope-parallel erosional rills down canyon walls, talus and debris fields without sediment drape, and gravel-laden canyon floors. These observations corroborate previous recent findings indicating submarine canyons host widespread albeit small scale geological activity during sea level highstands.