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ABSTRACT

The path of Bryant Canyon was identified during the structural and sequence stratigraphic mapping of reprocessed, migrated, 72-fold seismic data in the Garden Banks OCS area. The canyon pathway winds around and through salt structures in Garden Banks and continues to the south where it eventually overrides the allochthonous salt sheet that extends to the Sigsbee Escarpment. Stratigraphic evidence suggests that Bryant Canyon may be 0.2-0.3 Ma in age. It is now almost entirely infilled with shelf-derived (probably deltaic) sediments near the shelf/slope break and with turbidite and/or slump deposits farther down slope. Erosional features and reentrants in paleoshelf margins suggest that earlier canyons may also have occupied this pathway. The path of Bryant Canyon may be a primary and long standing conduit for shelf-derived coarse clastic sediments being transported into deep water.

Sediments and sedimentation associated with Bryant Canyon have affected salt body geometries observed within the Garden Banks area in three ways. First, updip and lateral differential loading by sediments infilling Bryant Canyon helped drive salt migration. Variations in size and location of these differential loads influence the direction and rate of salt flow. Second, sediment transported down Bryant Canyon has physically eroded and incised certain salt structures. Although rare, deep water erosion and dissection of salt structures directly affects their observed geometries. Third, erosion has removed the sediment covering some shallowly buried salt structures thus exposing them to sea water. Geometries of the exposed structures are affected by both the disruption of isostatic equilibrium and by the effects of salt water dissolution.

Nearest the shelf margin the effect of differential sediment loading is most advanced. There, sedimentation has dissected the allochthonous salt into closely spaced salt stocks. Farther down slope the dissection process is less complete. Bryant Canyon intersects and parallels a dip-oriented salt ridge. In southernmost Garden Banks, the effects of differential sediment loading are least advanced. Sediment transported down Bryant Canyon has created a series of dip-oriented salt-free fensters within the continuous allochthonous salt sheet.

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