Pressure Solution Slip-faulting Associated with the Quatal Thrust Fault
Kevin Mass
Whittier College
spy2000@starquest.net
Mentor: Jan Vermilye, Whittier College
This project is based on the analysis of pressure solution strain measurements to infer stress orientations. Vermilye and Seeber [1999] conducted similar research on the San Cayatano fault. We plan to apply this same methodology to the Quatal fault.
Pressure solution involves the process in which grains dissolve along the contacts where compressive stress is the greatest. Evidence of pressure solution is contained in the sandstone and conglomerate outcrops throughout the region. In conglomerates, the squeezing together of cobbles results in indentations on the cobble surface. This indentation forms perpendicular to the maximum compressive stress. These strain measurements can be analyzed to infer the principal stress orientations.
Other deformation structures, such as small
pressure solution slip-faults, can be used to infer the principal
stresses. Field measurements of fault orientations and displacements
are taken at many locations. The data are analyzed using the methodology
of Michael [1984] and a program by Allmendinger et al. [1989].
Each field location are analyzed in order to interpret the principal
compressive (s1) and extensional (s3) axes. Since the Quatal fault
is a thrust fault, we expect the inferred stresses to reflect
a typical thrusting regime, with sub-horizontal compression and
near-vertical extension. Finally, we offer possible explanations
for the variability of stress orientations between individual
locations.
Table of Contents
Pressure Solution Slip-faulting Associated with the Quatal Thrust Fault