Steve Hall1, Tim Smith2
(1) BP Amoco, Houston, TX
(2) BP Amoco, Houston
ABSTRACT: Compressional Salt Diapirs In The Deepwater US Gulf Of Mexico
A compressional diapir is defined as a salt diapir that is derived from the crest of a thrust related compressional structure. Good examples exist in the Gulf of Mexico, including Green Knoll, which is described in this paper. Green Knoll is a well exposed solitary diapir displaying strong seabed relief. It is located in the SE corner of the Green Canyon protraction area. It is sourced from a NW vergent ramp anticline, part of the Atwater fold-belt, that can clearly be mapped extra salt. Both section and map restorations over the structure are described, which suggest the following evolution:-
1) Middle-Late Jurassic: NE trending relief was developed, with thicker salt being to the NW of the ridge. 2) Cretaceous-Middle Miocene: salt was withdrawn from the north, and a salt cored pillow with possible seabed relief and minor extensional faulting was formed (analog structure to the SW of Green Knoll). 3) Late Miocene-Early Pliocene: compression lead to the development of a NW vergent thrust, which detached within the salt, and was nucleated over the crest of the pillow. Additionally, the hanging wall was eroded, and a salt flow conduit was formed close to sea-bed. 4) Middle Pliocene-Pleistocene: salt continued to flow through the conduit, as it withdrew from within the main salt basin, and from the surrounding area, generating a salt withdrawal syncline around the structure.
Two main trap types are proposed: 1) seal against salt, 2) seal against an unconformity. The prospect is highly dependent on the hangingwall dip.
AAPG Search and Discovery Article #90906©2001 AAPG Annual Convention, Denver, Colorado