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. 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) Deformation in Conglomerates and Other Fragmental Rocks
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 have worked on a collaborative project with Dr. Basil Tikoff at UW-Madison and Dr. Eric Horsman (now at Eastern Carolina University) 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 was funded by the Tectonics program of NSF. See award abstract.
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. Amy Nachbor worked on geochemistry XRF measurements for her MS thesis. Kim Johnson and Christy Barszewski are currently working on parts of this project for their MS theses, using FTIR to measure water content in quartz grains, UWM’s XRF facility to quantify changes in chemistry across the strain gradient, and cathodoluminescence to look at deformation textures. 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.
Graduate student Andrew Parisi is doing a follow-up project relating to this work by using a technique to estimate the local strain in three-dimensions.
3) The Baraboo Quartzite, cleavage refraction, and rheological contrasts
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. This project began as collaborative work with Dr. Carol Ormand when we began looking at the kinematics of folding in Baraboo. Undergraduate researcher Victoria Robison did some preliminary research to look at the boudinage in the Baraboo Quartzite to see how the boudin shape may help to elucidate rheology. Graduate student Jo Traut looked at the boudin shapes and cleavage refraction to further constrain rheologic parameters of deformation for her thesis project.
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. Graduate student Mike DeVasto worked on details of this project for his master’s thesis and developed a GIS technique to “map” deformed rocks at the grain scale. The work was funded by UWM’s RGI program.
5) Shear Zone Network Geometries
Shear zones often form in anastomosing geometrical networks. Dr. Prajukti Bhattacharyya from the University of Wisconsin-Whitewater and I have developed GIS techniques to quantify aspects of shear zone networking.
In a collaborative project with Dr. Jordi Carreras and Dr. Elena Druguet from Universitat Autònoma de Barcelona (Spain) and Dr. Peter Hudleston from the University of Minnesota, we studed network formation in the Rainy Lake region.
As a follow-up project to this work, graduate student Ernie Thalhamer is studying shear zone network geometries in the same gabbroic rocks for his MS thesis.
6) Syntectonic Plutons
I am just starting a new project with Dr. Basil Tikoff at UW-Madison to study the emplacement of plutons in the northwest Scottish Highlands. Graduate student Justin Calhoun is working on this project, focusing on AMS (magnetic fabric technique) and microstructural analysis.
7) 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.
8) 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 information about published papers related to these and other studies, see the Publications Page.
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!