Structure-Tectonics

David Brumbaugh: Geophysics & structural geology

Research activities

Mechanics of normal and thrust faulting; earthquake source mechanics; Cenozoic tectonics of the southern Colorado Plateau and transition zone; earthquake studies of the North Anatolian fault zone, Turkey, and the Aleutian plate boundary.

Ernie Duebendorfer: Structural geology & tectonics

Research activities

My research interests lie in the fields of structural geology and tectonics and are quite broad. All of my research projects are strongly field based and many are augmented with petrographic, microstructural, and microprobe work. In addition, I work regularly with U/Pb and 40Ar/39Ar geochronologists to constrain the timing of deformational events. I currently have two active research projects.

Proterozoic accretionary tectonics in the southwestern U.S. The period between 1780 and 1650 Ma was one of major crustal growth in North America. Crustal growth occurred by the generation, collision, and amalgamation of juvenile crustal material such as oceanic island arcs and their associated basins, magmatic additions to the crust through rifting and, possibly, the involvement of fragments of older continental crust. This accretionary episode was similar in scale to the addition of numerous “suspect” terranes to western North America in the Mesozoic. A complicated and enigmatic boundary zone between the Mojave and Yavapai Proterozoic crustal provinces occurs in northwestern Arizona. Determining the timing and mode of juxtaposition those provinces and the manner in which isotopically mixed crust is formed are the primary objectives of this work.

Tertiary extensional tectonics in southern Nevada and northwestern Arizona. The Lake Mead area, southern Nevada and northwestern Arizona, has been the locus of large-magnitude extension (perhaps as much as 300%, according to some workers) in the middle Miocene and studies in this region have been the basis for development of several models for crustal extension. A major question has centered on the types of structures that have accommodated extension, specifically, the relative roles of strike-slip and detachment faulting. An outgrowth of this project focuses on how along-strike variations in displacement along large-scale, low-angle normal fault systems (detachments) are accommodated.

Selected Publications of Ernie Duebendorfer

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Duebendorfer, E.M., Chamberlain, K.R., and Fry, B., 2006, Mojave-Yavapai boundary zone, southwestern United States: A rifting model for the formation of an isotopically mixed crustal boundary zone: Geology, v. 34, p. 681-684> 

Duebendorfer, E.M., Chamberlain, K.R., and Heizler, M., 2006, Filling the North American Proterozoic tectonic gap: 1.60-1.59 Ga deformation and orogenesis in southern Wyoming, USA.: Journal of Geology, v. 114, p. 19-42.

Fryxell, J.E., and Duebendorfer, E.M., 2005, Origin and trajectory of the Frenchman Mountain block, an extensional allochthon on the Basin and Range province, southern Nevada: Journal of Geology, v. 113, p. 355-371.

Ferguson, C.B., Duebendorfer, E.M., and Chamberlain, K.R., 2004, Synkinematic intrusion of the 1.4 Ga Boriana Canyon pluton, northwestern Arizona: Implications for ca. 1.4 Ga regional strain in the western U.S.: Journal of Geology, v. 112, p. 165-184.

Duebendorfer, E.M., 2003, The interpretation of stretching lineations in multiply deformed terranes: An example from the Hualapai Mountains, Arizona, USA: Journal of Structural Geology, v. 25, p. 1393-1400.

Duebendorfer, E.M., and Vazquez, K.L., 2002, Penetrative strain at shallow crustal levels: The role of pressure solution in accommodating regional shortening strain, Ventura basin, western Transverse Ranges, California, in Barth, A., ed.: Crustal evolution of the southwestern United States: Geological Society of America Special Paper 365, p. 295-314.

Duebendorfer, E.M., 2002, Regional correlation of Mesoproterozoic structures and deformational events in the Albany-Fraser orogen, Western Australia: Precambrian Research, v. 116, p. 129-154.

Duebendorfer, E.M., Chamberlain, K.R., Jones, C.S., 2001, Paleoproterozoic tectonic history of the Mojave-Yavapai boundary zone: Perspective from the Cerbat Mountains, northwestern Arizona: Geological Society of America Bulletin, v. 113, p. 575-590.

Harlan, S.S., Duebendorfer, E.M., and Deibert, J., 1998, 40Ar/39Ar age determinations from Miocene volcanic rocks in the western Lake Mead area and in the southern Las Vegas Range: Canadian Journal of Earth Sciences, v. 35, p. 495-503.

Duebendorfer, E.M., and Sharp, W.D., 1998, Variation in extensional strain along-strike of the South Virgin-White Hills detachment fault: Perspective from the northern White Hills, northwestern Arizona: Geological Society of America Bulletin, v. 110, p. 1574-1589.

Duebendorfer, E.M., Nyman, M.W., Chamberlain, K.R., and Jones, C.S., 1998, Proterozoic rocks within the Mojave-Yavapai boundary zone, northwestern Arizona: Comparison of metamorphic and structural evolution across a major lithospheric(?) structure.

Duebendorfer, E.M., ed., Geologic Excursions in Northern and Central Arizona: Geological Society of America, Field Trip Guidebook, p. 127-148.

Duebendorfer, E.M., Beard, L.S., and Smith, E.I., 1998, Restoration of Tertiary deformation in the Lake Mead region, southern Nevada, in, Faulds, J., and Stewart, J., eds., Accommodation zones and transfer zones: The regional segmentation of the Basin and Range province: Geological Society of America Special Paper 323, p. 127-148.

Duebendorfer, E.M., Vermilye, J., Geiser, P.A., and Davis, T.L., 1998, Evidence for aseismic deformation in Southern California: Implications for seismic risk assessment: Geology, v. 26, p. 271-274.

Duebendorfer E.M., and Rees, M.N., 1998, Evidence for Cambrian deformation in the Ellsworth-Whitmore Mountains terrane, Antarctica: Stratigraphic and tectonic implications: Geology, v. 26, p. 55-58.

Paul Umhoefer: tectonics, basin analysis & structure

Research activities

My research is focused on Tectonics, especially active and young tectonics of Late Cenozoic time. My main research interest is in the tectonic evolution of, and processes that form, oblique plate boundaries. More specifically, I study basins and related faults that form in these settings, and the processes and evolution of areas with mixed strike-slip and dip-slip faulting. My research is field based and my students and I use the methods of structural geology, stratigraphy, and related disciplines to understand tectonic problems. The research I conduct is inevitably collaborative with researchers in many other fields, but especially in paleontology, sedimentology, geochronology, petrology, marine seismology, geodesy, and paleomagnetism.