In a related project, I am working with Dr. Adolph Yonkee at Weber State University to study deformed diamictites on Antelope Island in the Great Salt Lake of Utah. We are particularly interested in linking strain measurements with information about fluid interaction during deformation. Kim Johnson is currently working on part of this project for her master's thesis, using FTIR to measure water content in quartz grains and UWM's XRF facility to quantify changes in chemistry across the strain gradient.
Research Philosophy and Goals:
My emphasis in structural geology is to link structures in naturally deformed rocks
with processes of deformation using a variety of tools: field work, thin section
analysis,
mathematical models, physical analogue models, electron microscopy, and geophysical
techniques. In
deformed ductile rocks, resultant fabrics provide a record of the
deformation
history. Therefore, understanding the processes of fabric
development is an
important step in deciphering the history of deformed terranes and
solving the
fundamental problem of how earth materials respond to tectonic
forces. By
learning in detail how rocks deform, we can best characterize the
dynamics of
crustal materials. I am especially interested in addressing
fundamental
questions concerning rheology and deformation processes as
mechanisms for
production of structural fabric and the way in which fabrics vary
due to
lithologically controlled rheology contrasts at a variety of scales,
from
individual mineral grains to the terrane scale.
Some Present work:
1) Rheology and Conglomerates
Due to natural variations in the response to strain, heterogeneous
deformed
rocks such as conglomerates provide natural laboratories to observe
rheologically-controlled deformation. Polymictic conglomerates (those
with clasts
having a range of compositions), in particular, are ideal to study
rheologically-controlled deformation. By exploiting the natural
rheological
contrasts within the conglomerates, we hope to address the processes
of
deformation partitioning within rheologically heterogeneous rocks.
I am
currently working on a collaborative project with Dr. Basil
Tikoff and Dr. Eric Horsman
at UW-Madison to address this problem. Darlene Fissler also worked on this project for her master's thesis where she measured strain in the Seine conglomerates. Terra Anderson is currently working on part of this project for her master's thesis, using electron backscatter diffraction (EBSD) to measure the quartz crystallographic fabrics with increasing strain. We are using many techniques in this study including strain analysis, EBSD, and petrographic analysis. This work is funded by the Tectonics program of NSF. See award abstract. 2) Syntectonic Dikes and Veins- unravelling a strain history
I am working on a collaborative project with Dr. Jordi Carreras and Dr. Elena
Druguet
from Universitat Autònoma de Barcelona (Spain) in the Superior Province
near Rainy
Lake and the Cap de Creus region in Spain. We are looking at the complex field geometries formed with
multiple
intrusions during a prolonged deformation event. We have made
photomosaics of
boudined and folded veins and dikes and used the geometries
to unravel part of the deformation history. In future parts of this project, we are interested in developing a general model for dike orientations in transpression and studying how mechanical anisotropies in the host rocks control dike and vein emplacement geometries.3) The Baraboo Quartzite, cleavage refraction, and rheological
contrasts
This is a collaborative project with Dr. Carol Ormand.
Within the Baraboo Quartzite of south-central Wisconsin, there are
interbedded
shaly layers. We are looking in detail at the cleavage refraction
associated
with the layering and correlating that refraction with the
mineralogical or
fabric differences we see in the rocks. With undergraduate, Victoria Robison, we are also looking at the boudinage in the Baraboo Quartzite and how the boudin shape may help to elucidate rheology.4) The Mountain Shear Zone
This is a collaborative project with Dr. Prajukti Bhattacharyya at University of Wisconsin-Whitewater. We are using GIS technologies to characterize fabric features in gneissic rocks deformed by the Mountain Shear Zone and looking at small-scale changes in fabrics and mineralogy with increasing strain.5) Fabrics in Cataclasites and Deformation Bands
Graduate Student Becky Byars used mathematical functions called wavelets to characterize fabrics in cataclasite zones from north-central New Mexico. I would like to continue this work by using wavelets to characterize other aspects of cataclasite fabrics including compositional segregation of components.6) The Initiation and Development of Foliation Fabrics
I an interested in the processes of initiation and further development of fabrics in tectonites. Undergraduate Melissa Meeuwsen studied the role of competence contrasts in the localization of foliations for her independent progrect. I am continuing work in this area including petrographic analysis and EBSD of fabrics across a strain gradient. The work was funded by UWM's RGI program. For pictures of the field areas, see the Virtual Fieldtrip Page.
I am always looking for good students! If you are an undergraduate at UWM and are interested in learning more about structural geology or you are a student thinking of doing a graduate work (MS or PhD) in structural geology- please contact me. I'd be happy to discuss project ideas!