The Kaibab uplift is a Laramide-age (~90-50Ma) basement-cored uplift near the western edge of the Colorado Plateau.  Its curved but generally north-south-trending axis stretches from Flagstaff, AZ to near Bryce, UT. 

An interesting fault pattern exposed at the surface along the eastern limb of the Kaibab uplift was the focus of my dissertation research: fault geometries and slip vectors indicate that development of the Kaibab uplift involved a significant component of right-lateral offset that was previously not recognized.  The oblique offset roots into a reactivated basement fault at depth, and is tied to oblique convergence between the North American and Farallon plates during the Laramide orogeny.

Outer-arc extension commonly accompanies folding, so the presence of normal faults on the crest and in the steep monoclinal limb of the Kaibab uplift is not surprising.  What IS surprising is that some of the normal faults appear to preserve syn-tectonic sedimentation in strata that were deposited BEFORE the onset of Laramide deformation.  Are these really outer-arc normal faults associated with an early pulse of uplift, are they related to detachment along shallow, weak evaporites, or is there another tectonic cause of extensional faulting?

The origin of the Kaibab normal faults may be related to the origin of similar normal faults on the Rock Springs uplift in Wyoming.  Basil Tikoff and Selena Mederos are investigating the possibility that an early phase of deformation, perhaps driven by lithospheric buckling, occurred in the Rock Springs area.  I spent September in Rock Springs mapping and measuring normal faults and looking at sedimentation patterns, but more work remains to be done. 

In cooperation with structural geologists at Mobil Technology Comapny (now ExxonMobil), I ran a series of physical analog models to examine fault patterns that form in sedimentary cover over reactivated, oblique-slip basement faults.  Model resuts were essential in supporting the oblique-slip interpretation of the Kaibab uplift. 

An unexpected model result was the development of oblique normal faults on fold crests.  I am now designing a series of models to look specifically at factors influencing the orientations and distributions of outer-arc faults associated with basement-cored uplifts.

Deformation band shear zones (DBSZs) are brittle fault zones that accommodate volume reduction and shear offset during deformation of porous sandstones. DBSZs form by porosity reduction and cataclasis, such that the porosity of DBSZs is about an order of magnitude less than the sandstone host rock, and permeability is reduced by up to three orders of magnitude. DBSZs develop by the millions, forming a closely-spaced, interlocking network that can isolate small, impermeable compartments throughout an otherwise porous and permeable sandstone.

Joints are planar, opening-mode fractures that frequently accommodate layer-parallel extension.  Joints are often ignored in considerations of petroleum reservoir permeability because larger features like faults and persistent fractures provide the primary pathways for fluid flow. However, a well-developed joint set may provide essential connectivity in porous sandstone reservoirs that are otherwise compartmentalized by deformation band shear zones (DBSZs).

The DBSZs in our study area display closely-spaced, open joints that do not extend into adjacent sandstone.  George Davis (University of Arizona) and I have been examining the relationship between joint spacing and DBSZ thickness, and our preliminary work has led to more interesting questions.  Is it possible to predict joint spacing based on rheology of DBSZs and their host sandstone?  Do DBSZ joint orientations differ from regional joint sets? Can joints in DBSZs restore reservoir permeability? 

We (Eric Horsman and I) abandoned honey as a potential modeling material after one deliciously sloppy experiment.  We're now trying silicone putty, but the goal of the models is the same: to quantify particle rotations and velocity gradients associated with convergent flow. 
(What?)
We're forcing a viscous material to flow from a roomy reservoir through a constricted area, in order to find out what parts of the roomy reservoir (like the edges, the middle) flow out faster or slower, and to see if elongate markers rotate in a systematic way in order to make it through the constriction.
(How?)
We started with a simple experimental design that was not intended to replicate any natural system in any way: filming clear silicone putty with neutrally buoyant plastic markers flowing out of a funnel.  It worked pretty well - we have systematic results and consistent observations already, but we're making significant modifications to the experimental design and techniques in order to get better results.
(WHY?!)
We hope eventually to relate experimental results to rock fabrics developed during intrusion of dikes, sills, and lobes.  Results may also be applicable to patterns of flow around rigid inclusions within ductile shear zones.