The lower continental slope of the northwestern Gulf of Mexico is underlain by shallow, allochthonous salt. Keathley Canyon is one of several large canyons that locally define the salt front, extending into the interior of the slope province. We studied multichannel seismic reflection profiles and bathymetric data to evaluate canyon morphology, origin, and evolution. The canyon can be divided into two morphologically contrasting parts: (1) the upper canyon, consisting of a narrow valley, and (2) the lower canyon, consisting of a broad reentrant. Unlike most other canyon systems, it contains no levees, tributary valleys, distributaries, nor the expected sedimentary fan at its mouth. Also, it is too far seaward to be related to rivers that, in other areas, have initiated ma y submarine canyons during sea-level lowstands.

Multichannel seismic reflection profiles provide evidence of salt control on the formation of the canyon. Beneath the upper canyon, laterally moving salt occurs as two large lobes and a smaller one in the middle. These salt wedges uplifted the continental slope and rise sediments and coalesced, resulting in a valley-like feature with walls of uplifted and deformed strata. Once established, the narrow upper canyon was preserved and/or steepened by erosive, gravity-controlled processes. In the downslope position, a broad bathymetric low in the interlobal area between the two large salt lobes forms the lower canyon.

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