Sandra J. Wyld
Ph.D., Geology, Stanford University, 1992
M.S., Geology, University of California, Berkeley
B.S., Geology, University of Illinois, Champaign-Urbana
My research interests focus on the structural and tectonic evolution of convergent plate margins. I am particularly interested in how convergent margins grow over time, and how the structural evolution of these margins can be related to plate tectonic interactions.
Current topics of specific interest include: (1) Characteristics and causes of space-time variations in the structural evolution of convergent margins, both along-strike and across-strike from the forearc to the backarc; (2) How and why structures are partitioned between different levels of the crust during deformation, and the consequences of this partitioning for the evolution of orogenic belts; (3) The relative importance of strike-slip faulting in the structural development of convergent margins and in the resulting distribution of allochthonous terranes; (4) Influences of plutonism on the timing and character of deformation and metamorphism in orogenic belts; (5) Techniques which can constrain the uplift/burial history and paleotopography within deformed terranes. In addition, I am interested in how sedimentation patterns within depositional basins are influenced by tectonism and how these patterns can be used as a means of elucidating both local structural histories and larger-scale tectonic processes.
One main region of study has been the Nevada and California portion of the U.S. Cordillera, working on the Mesozoic and Paleozoic tectonic history. Additional areas of study and/or interest are: the Paleozoic of the southern Appalachians, the Paleozoic and Mesozoic of the Canadian Cordillera, and the Mesozoic and Cenozoic tectonics of the Caribbean region.
My research is strongly field-based and attempts to address problems from both a fine-scale, process-oriented standpoint as well as from a regional to global tectonic perspective. Detailed mapping and structural analyses form the backbone of most projects, but these techniques are commonly coupled with complementary study of metamorphism, magmatism, sedimentation, stratigraphy and geochronology that may shed additional insight on regional tectonic processes. Students interested in working with me should have good field skills (including attendance at a field camp), and those interested in working on any of the projects out west should have the ability to work in remote and rugged areas with at least some camping and lots of hiking.
1) Cretaceous strike-slip faulting in the western U.S. Cordillera
This ongoing project focuses on evidence for major dextral strike-slip faulting in the U.S. Cordillera during Early Cretaceous time. Previous studies have documented or suggested dextral strike-slip faulting during this time frame in eastern California and western Idaho. We have found evidence for dextral strike-slip faulting of similar age within the intervening region of northwest Nevada and southeast Oregon, and we are hypothesizing that all these strike-slip systems represent related elements of a single structural boundary that accomodated several 100 km of dextral slip in the Early Cretaceous. Some of the exciting implications of this new work are as follows. First, our data and hypothesis suggests that all terranes located outboard (west) of this boundary have been displaced northward by several 100 km from their pre-Cretaceous position along the continental margin; this has profound implications for paleo-tectonic reconstructions of the U.S. Cordillera. Second, it appears that this major strike-slip boundary served as a fundamental weak zone in the crust that localized younger shortening deformation and emplacement of arc magmas.
This is a field based project that involves data collection in key areas from northwestern Nevada (region from Pyramid Lake to the Pine Forest Range near the Oregon border) to southeast Oregon (Pueblo Mountains) to the Blue Mountains province of east-central Oregon. In some areas, we are engaged in detailed mapping projects, whereas in other areas we are mostly engaged in sample collection for geochronology.
Some publications resulting from this project are listed below.
Wright, J. E., and Wyld, S.J., 2007, Alternative model for the Late Jurassic/Early Cretaceous tectonic evolution of the Great Valley Group, California, in Cloos, M., Carlson, W.D., Gilbert, M.C., Liou, J.G., and Sorensen, S.S., eds., Convergent margin Terranes and Associated Regions: A Tribute to W.G. Ernst: Geological Society of America Special Paper 419, p. 81-95, doi: 10.1130/2007.2419(04).
Wyld, S. J., and Wright, J. E., 2001, New evidence for Cretaceous strike-slip faulting in the U.S. Cordillera; and implications for terrane displacement, deformation patterns and plutonism: American Journal of Science, v. 301, p. 150-181.
Abstracts and Theses
2) Reconstructing displacements on known Cretaceous-Tertiary strike-slip faults of the northwest Cordillera, and revised interpretation of the Neoproterozoic-early Paleozoic tectonic evolution of the Cordillera
These two projects involved new analyses of existing data sets collected by other workers rather than collection of any new data by myself or colleagues, and resulted in two comprehensive regional overview papers and several abstracts.
Wyld, S.J., Umhoefer, P., and Wright, J. E., 2006, Reconstructing northern Cordilleran terranes along known Cretaceous and Cenozoic strike-slip faults: Implications for the Baja BC hypothesis and other models, in Haggart, J.E., Enkin, R.J., and Monger, J.W.H., eds., Paleogeography of the North American Cordillera: Evidence For and Against Large-Scale Displacements: Geological Association of Canada, Special Paper 46, p. 275-296.
Wright, J. E., and Wyld, S.J., 2006, Gondwanan, Iapetan, Cordilleran interactions: A geodynamic model for the Paleozoic tectonic evolution of the North American Cordillera, in Haggart, J.E., Enkin, R.J., and Monger, J.W.H., eds., Paleogeography of the North American Cordillera: Evidence For and Against Large-Scale Displacements: Geological Association of Canada, Special Paper 46, p. 377-408.
Both of these projects yielded an abundance of new testable hypotheses concerning the Neoproterozoic-Early Paleozoic and Mesozoic tectonic evolution of the North American Cordillera, that would be ideal for future on-the-ground studies and student projects. The most likely project areas would be in Oregon, Nevada, and/or California, although projects in the Appalachians are also possible.
3) Mesozoic tectonic evolution of the southern Caribbean
I am working with Jim Wright on the multi-institutional Continental Dynamics project investigating the origin of the Caribbean plate and the accretion of the Leeward Antilles to the Venezuela continental margin (see Jim's web site and links for more information). Together, Jim and I have been mapping the islands of Aruba, Bonaire and Curacao, collecting samples for geochronologic analysis, and reinterpreting the Cretaceous to Tertiary tectonic evolution of this part of the Caribbean.
Publications resulting from this project:
Wright, J. E., and Wyld, S. J., 2005, Origin of the Caribbean plate: Geological Society of America Abstracts with Programs, Vol. 37, No. 4, p. 85.
Wright, J. E., and Wyld, S. J., 2005, Origin of the Caribbean Plate: A View from Aruba and Curacao: 17th Caribbean Geological Conference, San Juan Puerto Rico: Transactions of the 17th Caribbean Geological Conference.
Wright, J.E., and Wyld, S. J., 2004, Aruba and Curacao: Remnants of a collided Pacific Oceanic Plateau? Initial Geologic results from the BOLIVAR Project: EOS Tranactions American Geophysical Union 85 (47), Fall Meeting, Suppl., Abstract T33B-1367.
Wright, J. E., and Wyld, S.J., 2004, Caribbean model for the Paleozoic tectonic evolution of the north American Cordillera: in 17th International Basement Tectonics Conference, 4-D Framework of Continental Crust - Integrating Crustal Processes through Time: Program with Abstracts, http://geoweb.gg.utk.edu/ibta04crust/meeting.html, p.81.
4) Early Mesozoic Intra-Arc and Back-Arc Tectonism (Nevada)
Wyld, S. J., Rogers, J. W., and Copeland, P., 2003
, Metamorphic Evolution of the Luning Fencemaker Fold-Thrust Belt, Nevada: Illite Crystallinity, Metamorphic Petrology, and 40Ar/39Ar Geochronology: Journal of Geology, v. 111, no. 1, p. 17-38.
Wyld, S. J., 2002, Structural evolution of a Mesozoic backarc fold-and-thrust belt in the U.S. Cordillera: New evidence from northern Nevada: Geological Society of America Bulletin, v. 114, p. 1452-1468.
Wyld, S. J., Rogers, J. W., and Wright, J. E., 2001, Structural evolution within the Luning-Fencemaker fold-thrust belt, Nevada: Progression from back-arc basin collapse to intra-arc shortening: Journal of Structural Geology, v. 23, no. 12, 1971-1995.
Wyld, S. J., 2000, Triassic evolution of the arc and back-arc of northwest Nevada, and evidence for extensional tectonism, in Soreghan, M. J., and G. E. Gehrels, eds., Paleozoic and Triassic paleogeography and tectonics of western Nevada and northern California: Boulder, Colorado, Geological Society of America Special Paper 347, p. 185-208.
Abstracts and Theses
5) Pluton Emplacement Processes
Ciavarella, V., and Wyld, S. J., 2008
, Wall rocks as recorders of multiple pluton emplacement mechanisms - Examples from Cretaceous intrusions of northwest Nevada: in Wright, J. E., and Shervais, J.W., eds., Ophiolites, Arcs, and Batholiths, a Volume in Honor of Cliff Hopson: Geological Society of America Special Paper 438, p. 517-550, doi: 10.1130/2008.2438(19).
Veronica C. Ciavarella, Dept. of Geology, University of Georgia, M.S. degree received, 2003. Title of thesis: “Mesozoic deformation and pluton emplacement in the northern Luning-Fencemaker fold-and-thrust belt: New evidence from the Bloody Run Hills, Nevada” (131 pp.).