Christine Siddoway -- Associate Professor of Geology

Research Grants

Current Grant

Collaborative research: Gneiss dome architecture: Investigation of form and process in the Fosdick Mountains, West Antarctica, NSF-OPP 0338279, 36 months, $158,046.

The focus of this project is a migmatite gneiss dome in the Fosdick Mountains, Marie Byrd Land, Antarctica, where exceptional 3-D exposures can be used to determine dome architecture, explore the role of partial melt networks, and identify emplacement mechanisms. This dome has been interpreted as a product of extensional exhumation (Richard et al. 1994). This is a viable interpretation from the regional standpoint, because the dome was emplaced in mid-Cretaceous time during the rapid onset of divergent tectonics along the proto- Pacific margin of Gondwana. However, the complex internal structures of the Fosdick Mountains have yet to be considered and alternative intepretations need to be explored, such as upward extrusion within a contractional setting or lateral flow within a transcurrent attachment zone. The investigations will improve our general understanding of the role of gneiss domes in transferring material and heat during mountain-building, and of the behavior of the middle crust during a change from divergent to convergent tectonics along the active margin of Gondwana.

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). http://www.nsf.gov/cgi-bin/showaward?award=9615282

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