How Do Submarine Canyon-Channel Systems (re)Shape Continental Margins?
Submarine canyon-channel systems are the primary conduits transporting sediment from continental shelves to ocean basins. Accordingly, the sediment distribution (erosion, deposition, and transport) patterns of these conduits should influence the geomorphology and stratigraphy along continental margins. To explore canyon-channel evolution and its relationship to continental shelf-to-basin profiles, we use depth-slope profiles to compare and classify the morphologies of 50 modern submarine canyon-channel systems and related continental margins (25 passive-margin and 25 active-margin examples).
We hypothesize that, if unaffected by external forcing (e.g., tectonics), erosive and depositional forces will move channels and continental margins toward graded (equilibrium) profiles with low maximum slope, minimal slope inflections, and an overall smooth slope profile. We consider such systems ‘mature,’ whereas characteristics of ‘immature’ systems include high maximum slope, multiple inflections and highly irregular slope profiles. For slope profiles of both channels and continental margins, we divided the spectrum of maturity into 5 categories based on qualitative and quantitative metrics, including unsupervised machine learning (factor analysis). Quantitative relationships indicate that canyon-channel and continental margin morphologies (on both active and passive margins) do not mature together at consistent rates. Continental margin maturity typically lags behind channel maturity, and ‘mature’ canyon-channel systems develop on margins spanning the full range of maturities.
We propose endmember pathways (erosion vs. deposition dominated) by which canyon systems can achieve mature, graded profiles and use two-dimensional geometric models to explore the implications for the preservation and evolution of stratigraphic architecture. These results suggest three important conclusions: 1) Continental margins are typically less mature than associated canyon-channel systems. 2) The relative importance of incision vs. deposition on the evolution of a canyon-channel system appears to vary between systems, likely due to relative differences in maturity, sediment supply, and tectonism. 3) The relative importance of erosional vs. depositional processes drives the evolution of a canyon-channel system and therefore affects the depositional stratigraphy of the system near the canyon-channel transition.
AAPG Datapages/Search and Discovery Article #90350 © 2019 AAPG Annual Convention and Exhibition, San Antonio, Texas, May 19-22, 2019