Bob Wintsch

Robert Wintsch

Professor of Geological Sciences
Metamorphic Petrology, Structural Petrology, Tectonics, Geochronology

Office:   GY325
Phone:   812-855-4018
Email:   wintsch@indiana.edu

Educational Background

  • Ph.D., 1975, Brown University
  • B.A., 1969, Beloit College

Research Interests

Research of Wintsch and students working with him spans several aspects of metamorphic geology, from diagenesis and low grade metamorphism in slaty rocks to high grade metamorphism and partial melting. Much of this research focuses on identifying the relationships between deformational and metamorphic processes, from the grain scale and pressure solution to the scale of terranes and terrane assembly.

Recent Research Projects

Analysis of Suspect Terranes

Much of our most recent work has dealt with the identification of suspect or exotic lithotectonic terranes in the Appalachians, and with the history of terrane accretion.

Our approach is a multidisciplinary one that requires a variety of techniques. It relies on field work, where we try to understand the significance of ductile faults, which mark the boundaries of most terranes.

We sample and analyze metamorphic assemblages within terranes to try to identify discontinuitites in metamorphic grade. This work is done on the IU campus, but we date minerals by 40Ar/39Ar and U-Pb methods by collaborating with isotope geologists at the USGS, again to identify discontinuitites in the time of metamorphism or of cooling from metamorphic conditions. Some of our work is in the southern Appalachians, but we have worked most intensively in southern New England. We have begun work in central New England, where we collaborate with geologists from Massachusetts, New Hampshire and Maine, and again with USGS geochronologists.

Analysis of Suspect Terranes

Low Grade Rocks and Slaty Cleavage

 Low Grade Rocks

Wintsch is working on low grade rocks with the goal of identifying the reactions that occur during diagenesis, and determining if these reactions occur in environments closed or open on the scale of a hand specimen. The degree of openness is being inferred through determining whether the progress of these reactions correlates with changes in the bulk composition of the whole rock. A related study is looking at the mudstone to slate transition, to determine if pressure solution of mudstones could release, or "mobilize" major components for recycling in the upper crust. Collaborative work on fission track ages in apatite and zircon helps to inductively reconstruct the loading and unloading history of sedimentary basins.

 

Mylonites and Fault Rocks

Mylonites

We are exploring the relationships among chemical and mechanical processes in metamorphism, and especially in fault zones, where mechanical processes are relatively important. Chemical processes turn out to have a relatively large role in the evolution of fault rocks, from pressure solution-like dissolution/precipitation reactions in a near closed system, to reaction softening and reaction hardening in relatively open systems. We have identified ductile processes in very shallow fault zones where brittle deformation is expected, and evidence for brittle (seismic?) deformation in rocks as high grade as the sillimanite zone, where ductile deformation is expected. We have been working on fault rocks from the Moine thrust, Scotland, Insubric line southern Swiss Alps, and the northern and central Appalachians.

Recent Graduate Student Projects

Deasy, Ryan T. M.S. 2015. "The bedrock geology of western New Haven Quadrangle, Connecticut."
Document URL

Fetherston, Daniel B. M.S. 2014. "Alleghanian Metamorphism of the Southern Narragansett Basin, RI: Thermobarometric Constraints on Burial and Exhumation." Document URL

Cola, Elizabeth C. M.S. 2014. "Deformation-induced development of kyanite and fibrolitic sillimanite in monzodiorite orthogneiss, southwest Connecticut." Document URL

Undergraduate Projects and Opportunities

There are opportunities for student participation in field, analytical, and in some cases geochronologic work, and we are flexible about what kinds of problems to approach and where field relations can most effectively be addressed.