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Pacific NW Geologic Mapping Project

Geologic maps of the North Cascades

Tcao-1. Monolithologic granitic breccia in Oligocene Big Bosom Buttes caldera (Tcao). Caldera deposits overlie extensional sandstone beds (Tes). View southwest across Silesia Creek. Dashed lines are approximate contacts between geologic units. View image without annotation
Other photos that show unit Tcao:

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Photo Indices: Captions (Additional photos home) | Map | Young rocks and deposits | Older rocks west | Older rocks east