Comparison of submarine gully morphologies in passive and active margin settings

Abstract:

Passive and active tectonic margins have inherently different hypsometry, due to local patterns of

deformation and subsequent impacts on the style of sedimentation. One way we can analyze and

compare the two settings is through observation of submarine gullies, which are small channel

features that form along the continental slope as it descends to the ocean floor. By documenting

the geometries of gullies that have formed on passive margins and gullies that have formed on

active margins, we attempt to distinguish differences in gully morphologies in these two settings.

We manually mapped over 600 gullies and interfluves from shaded relief and contour maps

generated from bathymetric data across the globe, including the coast of California, the Beaufort

Sea, and the Black Sea. We extrapolated and plotted elevation profiles of the gullies along their

downslope distance, and compared a range of gully properties, such as length, spacing, and

slope, to look at the correlations among those elements of gullies and their tectonic setting. We

find that gullies forming on active margins show the greatest variability in their slopes,

exhibiting both the steepest and the shallowest slopes of the dataset. The slopes of the passive

margin gullies fall within the range of the active margin gully slopes, but interestingly, we note

patterns in the ranges of gully steepness at different localities. These results differ from our our

anticipation that active margin gullies are steeper than passive margin gullies, but suggest that

gullies in all settings display a variety of morphologies. Additional mapping of active margin

gullies will better determine if there are morphological differences between the two settings.