Development of Middle Cretaceous Canyons in the Nova Scotian Margin: Significance/Nature of Gravity-Driven Deposits and Their Relationship With Slope Background Sedimentation

Abstract

The middle Cretaceous stratigraphic succession (Logan Canyon Formation) in the Nova Scotia margin has been described as a shale-prone interval with few sandstone units. However, seismic mapping shows that canyon incision and channels are ubiquitous across the margin, even though there are variations in the frequency and distribution of these sedimentary pathways. The presence of canyons, several kilometers wide and hundreds of meter thick, which incised the entire slope region beyond the salt deformation domain, suggests that gravity-driven flows were able to take advantage of these pathways and reach areas to the west of the New England Seamounts within the Sohm abyssal plain. In contrast, areas outside the canyons present seismic facies that are typical of background slope sedimentation where there is poor evidence for the presence of gravity-driven deposits. These basic observations trigger a series of questions regarding the nature of deep-water systems in general: (1) What is controlling the location of these mega-canyons? Is it possible that major transform faults affecting the margin could be defining long-lived, underlying structural controlled corridors that helped position these mega-canyons during the Middle Cretaceous?, (2) What is the nature of the vertical and horizontal stacking of sediment-gravity deposits within these canyons? What portion corresponds to deposits generated by turbidity currents versus mass-wasting events? What portion of the sediments is derived from the margins of the canyon versus the outer-shelf? and 3) What is the relation between the source and catchment areas and the length of these deposits? Answering some of these questions could bring useful insights into the nature of ancient deep-water stratigraphic systems.

AAPG Datapages/Search and Discovery Article #90291 ©2017 AAPG Annual Convention and Exhibition, Houston, Texas, April 2-5, 2017