Quantifying the relative influence of ice sheets, faults, and instability on channel and gully cross-profile shapes in the Gulf of Alaska

Convergent tectonics and glaciomarine sedimentary processes in the northern Gulf of Alaska have produced a variety of troughs, canyons, channels, gullies, and other drainage related features over a range of spatial scales. To evaluate the effects of glaciomarine and fault processes on observed drainage morphology we measured regional drainage feature cross-profile shape characteristics across the area. Our results show overlap between U-shaped feature cross-profile locations, ice sheet extents, and instability zones on the shallow shelf and slope that were previously inferred by observations of potential mass-movement structures such as slumps, slides, and debris flows. U-shaped profiles were also observed in areas of recent slope progradation such as the flank of the proximal deep-sea Surveyor Fan. We used principal component analysis (PCA) and geographically weighted regression (GWR) to relate drainage cross-profile morphology to proxy variables for ice sheets, faults, and instability zones. This method enables quantitative evaluation of the effects on cross-profile shape explainable by each variable as indicated by the magnitude, distribution, and variation of parameter coefficients both at the local and regional scale. Our multiple variable GWR model can explain most of the regional variability in cross-profile shape with the contribution of each parameter varying throughout the study area. Parameters associated with ice sheet extent have the strongest overall relationship with drainage shape, while the distance from an instability zone is the strongest local relationship. The fault proxy parameter shows relatively strong correlations with cross-profile shape near the Transition Fault, and the narrowest zone of morphologic influence overall.