Systemic Stratigraphy

Seminar

A salt interval (colored in purple), deposited near the bottom of the margin, induced a significant tectonic disharmony between the infra and supra-salt sediments. Such a salt induced tectonic disharmony, matching the bottom of the salt and/or primary correlative salt-welds* (double red dots), separates deformed (lengthened by normal faulting) from undeformed sediments (infra-salt margin sediments). Two high angle fault planes, injected by salt, seem to be associated with reactivated fracture zones that affect not only the Gondwana basement, but the Atlantic-type divergent margin as well. These faults defined faulted-blocks that played with a movement similar to that of piano keys. Such tectonic movement creates local compressional tectonic regimes (σ₁ horizontal) responsible of the shortening visible in restricted areas of the margin. It is important to differentiate the uplift of the sediments induced by the local compressional tectonic regimes from the uplift induced by the halokinesis** (salt diapirs ). In the first case, the uplifted sediments are shortened, while in the second they are lengthened. It can be said, the margin sediments were lengthened by the continuous seaward tilting and by halokinesis, but they were also, locally, shortened by the recent movements of the old Gondwana fracture zones. This seems to be particularly true for the deformation of the red unconformity, on the upper part of the seismic line, which is, easily, recognized by the associated onlap seismic surface. At the level of such unconformity, which indicates a significant relative sea level fall, the fracture zones, seem to be the responsible for the upper and lower limits of the continental slope.
*Surface or junction zone of strata, originally separated by autochthonous or allochthonous salt. A salt weld is a negative salt structure that results from a complete or nearly complete removal of the salt.

**Kind of salt tectonics in which the salt-flow is just due to its buoyancy (release of the potential energy of gravity). Halokinesis is induced by the lateral and vertical flow of evaporite levels in the absence of any significant lateral tectonic stress, i.e., in the absence of a compressive tectonic regime.
Summary:
- Depositional Model
- Depositional Coastal Break
- Paleo-Water Depth
- Accomodation
 - Bayline
- Sealevel Curve versus Tectonic Signal
- Exercices
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