G. Schreurs¹, R. Hänni¹ & P. Vock²

¹Institute of Geological Sciences, University of Bern, Baltzerstrasse 1, CH-3012 Bern, Switzerland
schreurs@geo.unibe.ch
²Institute of Diagnostic Radiology, Inselspital, CH-3010 Bern

Abstract

Analogue model experiments were done to study the influence of brittle-viscous multilayers on faulting during rifting. In each experiment a lower viscous layer was placed over the entire base of the model, whereas a second interbedded viscous layer separated lower brittle strata from upper brittle strata. The presence of an interbedded viscous layer led to the development of two independent, decoupled conjugate normal fault systems in upper and lower brittle strata. Initial width between conjugate faults depended on the thickness of the brittle strata overlying a viscous layer. With progressive extension, fault-bounded blocks rotated about horizontal axes. Rotations of these fault blocks and accompanied lateral viscous flow caused locally reverse faulting in upper brittle strata. Continued extension eventually led to local linkage between faults in lower and upper brittle strata. Location and orientation of extensional transfer zones were directly linked to the geometry of the interbedded viscous layer. Where the initial boundaries of the upper viscous layer were parallel to the extension direction, the strike of the transfer zones was also parallel. Where this boundary was oblique, the strike of the transfer zones was also oblique.

Single stage rifting - Experiment 77

Multiple rifting - Experiment 78