Study of Multilayer Wrench-Fault System Using Rock Models Deformed Under Confining Pressure

Ching-Weei Lin

Rock models are deformed under 600 bars confining pressure to evaluate the influence of structural stratigraphy (mechanical layering) on the deformation of a multilayered wrench-fault system. Specific objectives of this study are to investigate the effects of lithology and thickness of layering on the progressive development of structures, strain distributions, and deformation fabrics within the wrench-fault zone in space and time.

A stratigraphic sequence consisting of limestone (or sandstone) and lead is subjected to strike-slip displacement along a lubricated 45° pre-cut in an underlying sandstone forcing block. It is deformed at an average displacement rate of 1.0 × 10^-4 cm sec^-1 at room temperature and dryness and at 600 bars confining pressure. Experimental parameters to be studied include (1) ratio of limestone to lead, (2) thickness of the lead layers, and (3) loading conditions across the ends of the specimens. The forcing block is sandwiched between two sets of sedimentary layers consisting of lead and limestone plates, thereby providing two sets of data (i.e., models) for each experiment.

Displacement along the 45° precut in the forcing block produces both strike-slip and dip-slip displacement along the precut and within the lead/limestone veneer. Results to date indicate that as the ratio of lead to limestone and the thickness of the lead increase, the fracture density decreases in the limestone along the wrench fault above the lead and drape-folding of the limestone is favored over faulting.

AAPG Search and Discovery Article #91025©1989 AAPG Midcontinent, Sept. 24-26, 1989, Oklahoma City, Oklahoma.