DEVELOPMENT OF A PALEOGENE SALT CANOPY SYSTEM AND ASSOCIATED SEDIMENTARY RAFTS, WEST-CENTRAL DEEPWATER GULF OF MEXICO, U.S.A

Canopy salt in the deepwater Gulf of Mexico is the result of regional compressive forces remobilizing thick Jurassic salt first into salt stocks, then into salt lenses extruded onto the sea floor which laterally extend over great distance (10’s of miles/kilometers) primarily through gravitational forces. There is a close temporal correlation between the development of significant deltaic clastic depopods and the extrusion of deepwater canopy salt.

Canopy salt in the Garden Banks / Keathley Canyon protraction areas of the deepwater Gulf of Mexico typically overlay interpreted Oligocene–upper Eocene strata, indicating that this was the age of emplacement of a large regional canopy system in the subject area. This contrasts with the younger, generally Miocene, canopy emplacement in the east-central deepwater Gulf of Mexico, and a younger (Miocene-Pliocene) successor canopy system in the western Gulf.

Examination of the Paleogene canopy system reveals numerous rafts of lower Tertiary and Mesozoic strata preserved above the canopy. Norton (GB 754) and Vienna (GB 840) wells documented these rafts; reflection seismic data reveal many more probable rafts of similar seismic signature but uncertain age. These rafts originated as in-place strata deposited above autochthonous salt; subsequent canopy development dissected these roof rocks and transported them during allochthon expansion.

Recent well control reveals the presence of remnant raft section where the original canopy salt has been drastically thinned or welded, presenting a seemingly chronostratigraphically continuous seismic section. The Sumatra well (GB 941) penetrated subsalt section including blocks of upright and overturned Miocene strata overlying an intact Eocene-to-Mesozoic raft. This raft, originally lying on a Paleogene salt canopy, docked onto normal Oligocene section as the canopy deflated to a weld.

Examination of regional reflection seismic data reveals that the Sumatra salt weld can be correlated to intact Paleogene canopy, confirming the contemporaneous emplacement age and allowing better understanding of the emplacement and deformation history of the Paleogene canopy system. Numerous additional potential raft blocks have been identified on regional seismic data.