Christine Siddoway -- Professor of Geology

Research Grants

Current Grant

Collaborative Research: Formation of basement-involved foreland arches: An Integrated structural and seismic EarthScope experiment, $ 134,440. With M. Anderson (Colorado College), E. Erslev (U. Wyoming), Anne Sheehan (CU-Boulder), and Kate Miller (UTEP). NSF award number not available due to recent decision date.

This collaborative project is for integrated seismology and structural geology research in the Bighorn Mountains range of Wyoming. The research is funded by NSF Earthscope (www.earthscope.org), a multi-year initiative to explore the structure and evolution of the North American continent. Generally speaking, Earthscope seeks to determine the continent's configuration at the scale of the lithosphere, using diverse "remote sensing" techniques from geophysics. The Bighorns range is an optimal place to use seismology and structural geology to construct three-dimensional images of the North American lithosphere, at vastly greater scale but analogous to computed tomography (CT) or magnetic resonance imaging (MRI) models that are used in human medicine. The Bighorn Mountains form an vast structural arch that is an internationally known example of deformation in the interior of a tectonic plate, far from a plate boundary, and as such it offers extraordinary opportunities for this innovative research.

The project is a collaboration with investigators from three institutions in addition to CC. These are Colorado State University, University of Texas - El Paso, and the University of Colorado - Boulder. The field and laboratory studies will involve up to ten undergraduates from Colorado College over the three years of the project. The students will work closely together with the team of faculty and graduate researchers and undertake original investigations in seismology and structural geology that contribute to the overall aims of the project.

Prior NSF Grants

Collaborative Research: Air-Ground Study of Tectonics at the Boundary Between the Eastern Ross Embayment and Western Marie Byrd Land, Antarctica: Basement Geology and Structure (08/01/97 – 07/31/02). Award OPP-9615282, $114,972, Co-PIs: Christine Siddoway Bruce Luyendyk (UCSB).

Combined airborne geophysics and brittle fault studies have determined the crustal structure and kinematic history of the eastern Ross Sea margin in western Marie Byrd Land (MBL). Range-and-glacier topography at ~20 km spacing coincides with extended crust ~25 km thick determined from gravity modeling. Brittle faults and mafic dikes provide the first kinematic data for the region and record extension directed ~N70E at circa 105 to 95 Ma when most of the extension occurred. The finding is contrary to the prevailing view that ~N-S stretching, orthogonal to the rifted margin, was in effect at this time. An hypothesis that reconciles kinematic information from the regional brittle structures with the strain history of a localized exposure of middle crust (Fosdick migmatite dome) is for regional transcurrent strain induced by dextral oblique convergence between the Phoenix and Gondwana plates in Early Cretaceous time (Siddoway, 2004). We infer that ultimate breakup between MBL and New Zealand-Campbell Plateau occurred upon the transcurrent structures, and note that structural control by preexisting wrench structures accounts for breakup across the Ross Sea basin trends; the paucity of evidence for fault activity on land during 67 Ma breakup; and the rapid development of new plate boundaries without widespread deformation of adjoining crustal blocks. Six recent publications (Siddoway et al., in review; in press; 2004; Luyendyk et al., 2003; Stone et al., 2003) result from this work. Three undergraduate colleagues contributed to collection and interpretation of the kinematic dataset (Whitehead, 1999; Sass, 2000; and Cowdery, 2001). Geochemical investigation of Pleistocene basalts makes part of one doctoral thesis (Gaffney and Siddoway, 2004).

Collaborative Research: Contrasting Styles of Ca. 1.4 Ga Tectonism in the Southern Rockies: Evidence for a Fossil Rheologic Transition in a Deeply Exhumed Intracontinental Orogen (01/01/00-12/31/03). EAR-0101314, $30,504 , Co-PIs: K.Karlstrom, M.Williams, J. Connelly, C. Siddoway

Research in the Wet Mountains of Colorado focuses upon deeply exhumed Mesoproterozoic gneisses in a region hypothesized to have supported an intracontinental plateau developed during circa 1.4 Ga transpression along the southern boundary of Laurentia. The Wet Mountains expose a transition between partitioned strain, with deformation localized upon shear zones bounding coherent crustal blocks, and melt-dominated behavior supporting penetrative flow within migmatites. Potentially these ancient rocks provide an analog for the partial-melt horizon documented in contemporary orogenic plateaus, such as the Tibetan Plateau. Eight AGU and GSA abstracts and one field guide contribution result from this work (e.g. Leonard et al. 2002; Siddoway et al., 2002, 2001; Andronicos et al., 2002, 2001; Dean et al., 2002, 2001). https://www.fastlane.nsf.gov/servlet/showaward?award=0101314

1997 Collaborative International Research: Investigation of Structures, Structural Fabrics and Metamorphic Associations in Northern Victoria Land, NSF-OPP 9702161 https://www.fastlane.nsf.gov/servlet/showaward?award=9702161