Fault Development in the Madison Valley: Implications for Fault System Behavior and Passage of the Yellowstone Hotspot
Chenin, Julian B.
Cannon, John Matthew
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The Yellowstone hotspot has been migrating N55° E at ~25 km/m.y. since approximately 16 Ma creating a series of calderas in its wake. Locally, in the Madison Valley, E-W opening of the valley is investigated by detailed mapping near the Palisades Campground which shows an east-dipping, curvy planar, synthetic fault which offsets the 2.8 Ka HRT by 40 m. Initial field work suggested only E-W extension accommodated by faults striking N-S, at approximately 60° from each other along the Madison and Gravelly Range. However, further structural analysis of the fault fractures and regional geologic maps shows that the primary displacement zone is orthogonal to N-S basin and range structures and are part of a basin wide fault system. Therefore, a more complex, underlying mechanism is causing E-W and N-S extension. Reactivation of foliated surfaces in the metamorphic rock sequences in the Madison and Gravelly Range may explain this “anomalous” geometry. Alternatively, it is envisioned that as the hotspot moves, it creates a topographic welt known as the Yellowstone Crescent of High Terrain (YCHT). Based on its predicted geometry gravitational collapse of the welt could also explain an along strike change in E-W subsidence that could drive N-S extension.