Abstract
Eocene Basalt of Summit Creek: Slab breakoff magmatism in the central Washington Cascades, USA
Highlights
Throughout Washington, Oregon, and British Columbia, the early to middle Eocene was a time of unusually widespread magmatism, extension, and tectonic reorganization
Seismic anomalies in the mantle beneath the northwestern United States have been interpreted as detached fragments of the Farallon slab (Sigloch et al, 2008; Schmandt and Humphreys, 2011), suggesting that slab breakoff followed by rollback could have been the causal mechanisms for magmatism and uplift
To better understand the tectonic processes that occurred during the Eocene, we studied the Basalt of Summit Creek (BSC), a sequence of basalts and minor rhyolite exposed within the boundaries of the younger Cascade arc in Washington state (Fig. 1)
Summary
Throughout Washington, Oregon, and British Columbia (west coast of the United States and Canada), the early to middle Eocene was a time of unusually widespread magmatism, extension, and tectonic reorganization. 52 and 44 Ma, major tectonic events in this region included accretion of the oceanic Siletzia terrane in western Washington, Oregon, and British Columbia (Wells et al, 2014), voluminous and compositionally diverse magmatism in the Challis-Kamloops belt (Fig. 1), which extends from central Washington northward into Canada and as far inland as Montana (Ewing, 1980; Dostal et al, 1998; Bordet et al, 2014), broad regional uplift (Dumitru et al, 2013), extension manifested by core complex formation (Kruckenberg et al, 2008; Gordon et al, 2009), rapid basin subsidence (Evans and Ristow, 1994; Eddy et al, 2016), dike swarm emplacement (Tabor et al, 1984; Miller et al, 2016), and establishment of the Cascade arc (Vance et al, 1987; Christiansen and Yeats, 1992; Sherrod and Smith, 2000). Seismic anomalies in the mantle beneath the northwestern United States have been interpreted as detached fragments of the Farallon slab (Sigloch et al, 2008; Schmandt and Humphreys, 2011), suggesting that slab breakoff followed by rollback could have been the causal mechanisms for magmatism and uplift
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
