Experimental Modeling of Salt Tectonics During Rifting and Inversion

M. A. Durcanin
Rutgers University, Department of Geological Sciences

Scaled experimental models show that the presence of synrift salt strongly affects deformation patterns during rifting and subsequent basin inversion. In the models, wet clay represents rocks with brittle behavior, whereas silicone polymer represents rocks with ductile behavior (e.g., salt). The models have two phases of deformation: 1) an extensional phase producing a rift basin, and 2) a subsequent shortening phase. A ductile layer (putty), overlain by a more brittle layer (wet clay), represents synrift basin infill. During rifting, two fault-zones develop: 1) the main border-fault zone, and 2) secondary hanging-wall faults. In models without putty, all faults are basement-involved. In models with putty, cover deformation depends on the lateral extent of the putty layer. It is decoupled from basement deformation in areas with putty, but is linked to basement deformation in areas without putty. Putty diapirs form during extension, and putty withdrawal produces broad, shallow depressions. During inversion, shortening amplifies salt-cored anticlines and synclines into localized highs and deep asymmetric depressions, respectively. Some detached normal faults in the cover reactivate as reverse faults, whereas other faults (e.g., those near putty conduits) continue to have normal slip during shortening. Some putty conduits rejuvenated by contraction continue to extrude putty, whereas other putty conduits close forming vertical welds. The structural features observed on 2D seismic data from the Orpheus graben, offshore Nova Scotia, have similar geometric characteristics as the structural features in the experimental models, giving new insights into the tectonic evolution of this basin.

AAPG Search and Discover Article #90087 © 2008 AAPG/SEG Student Expo, Houston, Texas