Award Date: June 2011
John Garver, Professor of Geology, has been awarded a 4-year National Science Foundation grant in the amount of $231,779 for his collaborative research project with a faculty researcher at Carleton College. This project, entitled “Understanding the Provenance and Thermal Evolution of the Chugach Prince William Terrain in Southern Alaska” integrates with Prof. Garver’s work (and recent grant award) through the Keck Geology Consortium. The project involves the direct training, mentoring, and assessment of 18 undergraduate thesis projects through the Consortium, and includes travel to Alaska for hands-on field work.
This proposal seeks funds to investigate the provenance and thermal evolution of Campanian-Paleocene flysch of the Chugach-Prince William terrane in southern Alaska. This thick and extensive accretionary complex was intruded by near-trench plutons inferred to be related to an adjacent TRT triple junction, but the location of this terrane at the time of ridge interaction is under considerable debate. There are two prevailing hypotheses for its position of formation along the Cordilleran margin: 1) The CPW formed more or less in place and ridge interaction was related to the now subduction Resurrection plate; 2) the CPW formed far to the south, was intruded near 48-49°N, and was subsequently translated along the continental margin to Alaska. We will use U/Pb and ZFT ages of detrital zircon to unravel the source region of this accretionary complex and subsequent thermal history. To target unique and age-distinctive rocks in potential source pathways we propose to selectively target a small but highly significant population of Precambrian grains for analysis. Using a newly developed technique of dating cooling ages of low-retentive zircon, we will use radiation-damaged grains to evaluate the low-temperature thermal history of the CPW following low-grade metamorphism (lower greenschist and prehnite-pumpellyite). The possible formation of the CPW far to the south and subsequent translation along the continental margin is a defining event in Cordilleran tectonics. The accretion and translation affected adjacent and flanking basins such as the hydrocarbon-rich Cook Inlet basin. This research directly addresses several key problems in Cordilleran tectonics related to terrane formation, translation, accretion, and basin formation. We will advance methods of detrital U/Pb analysis by taking a new approach at targeting specific grain populations (here, Precambrian). We will also continue our development of using radiation-damaged zircon as a thermochronologic tool.