Gaullier, Virginie¹, Laurence Droz², Marina Rabineau², Eliane Le Drezen³, Alain Normand³, Juan Baztan², Gwenael Jouet², Guy Rothwell⁴, Sara Colas⁵, Giuseppe Verdicchi⁶, Antonio Cattaneo⁶, Cedric Bonnel⁷, Fabienne Duval³, Estelle Le Roux³, David Amblas⁵
(1) Université de Perpignan, Perpignan, France
(2) CNRS, 29280 Plouzané, France
(3) Ifremer Brest, Plouzané, France
(4) Southampton Oceanography Center, United Kingdom
(5) Barcelona University, Spain
(6) ISMAR, CNR, Bologne, Italy
(7)  Université Bordeaux I, France

ABSTRACT: Distal Multidirectional Contractional Salt Tectonics in The Deep-Water NW Mediterranean: Evidence from The PROGRES Cruise, North-Balearic Basin (Contribution to the EUROSTRATAFORM European Programme, Contract No EVK3-00200)

Plio-Quaternary tectonics in the Northwestern Mediterranean is dominated by gravity-driven gliding-spreading associated with thick Messinian evaporites, characterized by proximal extension, mid-slope translation, and distal shortening. In the North-Balearic Basin, the distal region comprises numerous circular or elongate diapirs whose rise was driven by combined shortening and sediment loading, rather than density inversion. Although these salt structures have been identified previously, very few high-resolution academic data were available until now to precisely determine their geometry and the associated structural features in the overburden.
During the recent PROGRES cruise (R/V “Suroît”, July – August 2003) we collected bathymetric data and back-scattering imagery using SIMRAD EM300 multibeam sounding system, 3.5 kHz profiles (CHIRP) and 6-channels seismic lines over the deep-water North-Balearic Basin, including in and west of the Rhône deep-sea fan.
Dip profiles (2000-2900 m water depths) clearly illustrate the different salt provinces (upslope domain, with listric normal growth faults, salt rollers, and rollover folds; midslope region with broad undulations; and downslope province with salt-cored anticlines and diapirs). Distal shortening is concentrated in a highly-deformed belt comprising, first a huge salt-cored anticline, a squeezed, thick sediment depocenter, and, more distally, a very large salt emergent diapir. At least three regional unconformities have recorded successive salt tectonics pulses. Downslope, the overburden is less deformed, except along the flanks of diapirs, whose size and number decrease basinward. Strike lines also show contractional features, indicating that shortening was multidirectional and was mainly accommodated by squeezing salt ridges whose stems often are pinched off entirely.

AAPG Search and Discovery Article #90026©2004 AAPG Annual Meeting, Dallas, Texas, April 18-21, 2004.