Salt Diapirism Generated by Shortening and Buckle Folding

Bruno C. Vendeville, UMR PBDS, Université de Lille 1, UFR Sciences de la Terre, Cité Scientifique - Batiment SN5, Villeneuve d'Ascq cedex, 59655, France, phone: +33 3 20 33 70 39, fax: +33 3 20 43 49 10, bruno.vendeville@univ-lille1.fr and Virginie Gaullier, LEGEM, Université de Perpignan, 52, Avenue Paul Alduy, Perpignan, 66860, France.

Seismic data from the Gulf of Lions show a series of large piercement diapirs at the downdip end of the system, in a region otherwise dominated by salt-cored folds. Can shortening or buckle folding lead to the formation of piercement diapirs? Piercement to the surface requires that the average density of the overburden exceeds the density of salt. For clastic sediment, this requires a thickness of 3750 m, a computation that varies depending on which compaction curves are used. It is thus difficult to imagine early piercement to the surface through a clastic overburden. Could shortening provide an answer? In salt-cored buckle folding, salt originally flows into the fold cores, and then is later forced back out as the fold tightens. However, if the synclines are grounded, there is no salt layer for the salt to flow back into. Continued tightening of the folds forces salt to rise up as it would in a diapir rejuvenated by shortening. This can lead to piercement, even if the overburden is less dense than the salt. Grounding of synclines is favored in a simple shear scenario, where the overburden is shortening more than the salt.

Improved Understanding of Plays Related to Salt and Shale Tectonics I
2005 AAPG International Conference and Exhibition (September 11-14, 2005) Technical Program