-Geologic Maps of the Panamint Valley region
Neogene extensional tectonic overprinting of Panamint Valley
I am currently working on deciphering the strain history of a complex transtensional system of active faulting in the Death Valley/Walker Lane region.
I have measured over 1000 fault planes with fault striae and I am in the process of separating these striae into distinct sets which reflect the multiple strain fields this area has experienced. Mesozoic striae are easily distinguished based on their eastward thrust sense and greenschist facies mineral striae and association with ductile deformation. Neogene (Miocene to Recent) striae have iron oxides associations and some obviously cross cut modern alluvial, and pluvial deposits and surfaces. More than one event of deformation has occurred during Neogene time and separating these events is more complex because there is no distinct metamorphic assemblage and often there is a lack of timing constraints. Once I can separate these, I can model the strain history and examine the changing geometries with time to try to explain the overly complex and non-intuitive nature of the active faulting.
Field-based Geographic Information Systems (GIS)
I am pursuing new approaches to collecting geologic information in the field (based on experiences with Doug Walker, my doctoral dissertation advisor). My current approach uses a lightweight, ruggedized laptop computer running GIS software. This digital field data collection system saves many weeks of office work digitizing my paper maps and notebook. Other huge bonuses are that I don't have to fold and unfold paper maps during a windstorm and I can easily update or append previous mapping.
This software allows mapping of any geologic data as points, lines or polygons at any scale and with any background spatial dataset you can get into a digital format. I have mapped using vectorized topographic contour lines (free from the USGS, but requires some tweaking to use them in ARCGIS), digital orthophotoquadrangles (free from the USGS), LANDSAT satellite images (USGS), Aster satellite images (USGS), digital elevation models (DEMs, also free from the USGS) and other digital data sets generated by me or others (see links page and my geologic maps page for examples of these data).
I have successfully used this setup in the harsh conditions of the Panamint-Death Valleys region of California. Despite temperatures of 110 to below freezing, windblown dust and sand, steep topography, jagged rocks, sudden rain and snow storms, and use as a not so comfortable pillow on afternoon naps at the top of mountains this system has been a success. No performance-debilitating damage has been done to the operator or the computer so far after about 9 months worth of field use.
So far I have used ARCVIEW and lately ARCGIS software by ESRI running on Microsoft Windows 98 and XP. For those without cushy university site licenses for expensive ESRI software and the latest field computer, I am setting up to experiment with using a cheaper setup on an older ruggedized computer (Panasonic Toughbook MF-34, pictured above, weighing 3 lbs. and purchased for $350 on E-bay,) running free GIS software GRASS with LINUX as an operating system.
Mesozoic arc-related deformation of the Panamint Range
My doctoral dissertation focused on a study of the tectonic evolution of the Panamint Range, California during the Mesozoic. The Mesozoic of the western North America was an active collisional boundary during much of this time. Many studies have looked at the timing and kinematics of deformation in this region but because of later deformation during the Cenozoic there was no know area in which all of the myriad deformations were seen together and so cross-cutting relationships were poorly constrained for closely-spaced (temporally) events. My approach was to identify and interpret deformational fabrics and to look for cross-cutting relationships of deformation fabrics and plutonic/volcanic bodies. I sampled the important igneous bodies and applied the U-Pb zircon geochronometer to calculate ages of emplacement and thus constrain the ages of the cross-cutting structures.
I am currently rewriting this data and interpretations of this study for re-submission for publication.
Cenozoic tectonics of Huizopa, Chihuahua, Mexico
I have collected fault plane and striae data along with dike, tension gash, bedding, joint and vein data of a little studied area along border of the Mexican states of Chihuahua and Sonora. This area is included in most geologic compilations as part of the great Sierra Madre Occidental ignimbrite-caldera field. While working here I have seen neither caldera or ignimbrite, creating some doubt about the extent of geologic knowledge in this region and wondering if things are only know next to roads. This area was previously unmapped at any usable scale. It is dominated by greater than kilometer thicknesses of basaltic-andesite lavas with local volcaniclastics and rhyolite lava flows tilted westward. These lavas are probably Oligocene in age, but nothing has been dated so far. I will examine the strain history of this area based on the paleostresses of structures and then I will be trying to fit that intot he poorly known regional tectonic framework.
Active
deformation of Io (a moon of Jupiter)
I have done a preliminary compilation of NASA Voyager, Galileo, and Cassini images from Io to look at systematic structures across Io. Io is the most active volcanic object known in the Solar System and structures observed there must be young based on the rapid resurfacing rate of Io. I am trying to examine what mechanism creates the high topographic relief of mountains on Io, for instance the 10 km relief of Tohil Mons. This analysis has been hampered by NASA's weird (but practical?) image format (Isis) and lack of adequate high-resolution coverage. I will be installing UNIX on one of my machines so I can start a more systematic process of structural analysis using NASA image software.