Mechanical Stratigraphy of Salt Induced Structures from Southern Gulf
of Mexico
Barrios, Jorge1, Felipe
Audemard2 (1) PEMEX Exploracion y Produccion, Villahermosa, Mexico
(2) Schlumberger - DCS, Mexico, Villahermosa, Mexico
3D reflection seismic data from the Salina Basin illustrate the style of
extensional -contractional nature of the structures
triggered by salt movement. Many times these are viewed as independent piercement structures. When evaluated in a regional context
these structures are developed from a specific mechanism coupled with the stratigraphy. This tectonic assemblage is defined by the
interplay of at least six different decoupling surfaces developed along well
defined stratigraphic intervals The
sedimentary sequence could be summarized into three major Packages which are rheologically independent. The uppermost Eocene-Recent
interval is essentially of siliciclastic nature. The
intermediate lime Paleocene – Upper Jurassic (Tithonian)
is mainly carbonate and the lower penetrated portion of the Jurassic is made of
siliciclastic and evaporites.
The seismic character underneath this sequence is interpreted as the
autochthonous plastic salt layer. Two salt packages are identified in many
places and correspond to the lowermost decoupled levels. The over pressured Tithonian source beds are locally a decoupling surface
adjusting the deformation associated with the salt cored structures. The interphase between the competent Mesozoic carbonate and the
overlain clastic unit is also a detachment surface at
regional scale. The shale rich Oligocene-Lower Miocene interval is an evident
decoupling layer associated to a very distinctive chaotic character. The
uppermost surface is hosted in the limits of the middle-Upper Miocene. In many
places the upper 2 surfaces constitute the sole of shale diapirs.
All these surfaces can be viewed as salt weld hosting allochthonous
salt masses commonly overlain by rotated sedimentary packages