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Distribution of Salt Keels in the Deepwater Northern Gulf of Mexico


The distribution of salt keels projecting below the base of allochthonous salt as observed on modern 3-D seismic data in the deep Northern Gulf of Mexico is not random. Although keels may form by several different processes, a suite of keels which form due to extension of sub canopy sediments on a detachment within Oligocene-to-Eocene strata have a unique profile and distinct location. Regional mapping of the base of the salt canopy reveals that keels of this type are found parallel to, but offset shelfward (updip) from the present day Sigsbee Escarpment. This relationship holds across all of Keathley Canyon OCS area and into the Alaminos Canyon OCS area. Keels formed by other processes do not show this unique pattern. The distanced between keel structures and the Sigsbee Escarpment varies from 10-30 km. The keel structure itself is not a single discrete feature but a series of linked smaller keels. Linkage style between keels appears similar to that for growth faults (relays). The location for detachment initiation and the orientation of individual keels can change markedly between salt lobes comprising the allochthonous canopy. The location for detachment initiation is often found in close relationship with deeper salt structures. Sparse well data indicate that the timing for displacement, which occurred after emplacement of the shallow canopy, is Plio-Pleistocene and therefore geologically quite recent. We speculate that the location where displacement initiates is structurally controlled and has relationships to deeper salt features and flexure points caused by updip crustal loading.