No abstract

We integrate new geochronological, petrographic, and geochemical data with previously published (Sierra Crest-Little Walker volcanic center) and new (Ebbetts Pass volcanic center) structural and stratigraphic data to describe two deeply dissected, spectacularly well-exposed Walker Lane pull-apart basins in the ancestral Cascades arc. The Miocene (ca. 12-5 Ma) Sierra Crest-Little Walker arc volcanic center and the Miocene-Pliocene (ca. 6-4.6 Ma) Ebbetts Pass arc volcanic center formed in pull-apart basins in the Walker Lane, a NNW-trending zone of dextral strike-slip and oblique normal faults at the western edge of the Basin and Range Province. The Sierra Crest-Little Walker arc volcanic center is a transtensional arc volcanic field that is as areally extensive (~4000 km Volcano-tectonic activity continued for a longer period (ca. 12-6 Ma) in the northern half of the Sierra Crest-Little Walker volcanic center than it did in the southern half (ca. 12-9 Ma), overlapping for ~1 m.y. with the onset of volcano-tectonic activity at the Ebbetts Pass volcanic center to the north. This provides local-scale confirmation of the regional-scale interpretation that a transtensional rift tip propagated northward with time within the arc axis, in concert with northward migration of the Mendocino triple junction. Transtensional rift magmatism followed in its wake and continues today at various points along the length of the Walker Lane. "Tectono-stratigraphic recycling" was a key geologic process throughout the development of these ancestral Cascades arc pull-apart basins, and it consisted of the transfer of megaslide slabs, up to 2 km long and tens to hundreds of meters thick, from footwall to hanging-wall blocks in the transtensional rift. A time-slice series of block diagrams is used to illustrate the structural controls on arc volcanism in the early stages of Walker Lane transtensional faulting (ca. 12-4.6 Ma).

2015. Donna's current interests center around education issues in general, and in particular on increasing access and success of those traditionally under-represented and/or under-served in STEM higher education.