High-resolution temporal records of magmatism, sedimentation, and faulting at evolving plate boundaries

Abstract

This dissertation uses high-precision U-Pb zircon geochronology to document the spatial and temporal distribution of magmatism, deformation, and sedimentation during Paleogene ridge-trench interaction in western Washington. Chapter 1 creates a regional stratigraphy for nonmarine sedimentary and volcanic rocks throughout central and western Washington and demonstrates that the depositional history of these rocks is consistent with accretion of over thickened oceanic crust (Siletzia terrane) and passage of a triple-junction. Chapter 2 establishes the volcanic stratigraphy of northern Siletzia and show that it is consistent with its origin as an accreted oceanic plateau, possibly developed above a long-lived Yellowstone hot spot. Chapter 3 quantifies magma emplacement rates in a large, granitoid intrusive complex (Golden Horn batholith) that was emplaced during Paleogene ridge-trench interaction. Parts of this batholith were constructed at the highest rate ever documented in a large granitoid intrusive complex (~0.0125 km³/a). This high emplacement rate may be related to its unique tectonic setting. The second tectonic setting is the rift-to-drift transition in the Newfoundland-Iberia rift. This rift is considered the type example of a magma-poor rifted margin and both margins consist of broad areas of exhumed subcontinental lithospheric mantle. Chapter 5 documents time-transgressive magmatism from east to west across both margins and suggests that mantle was exhumed during a single period of detachment faulting.