Physical Sciences and Mathematics Commons^™

Using Paleomagnetism To Unravel The Mysteries Of The Summit Creek Basalts, Glynis Bawden

Summer Research

The Summit Creek Basalts are a sequence of steeply dipping subaerial late Eocene basaltic flows located southeast of Washington’s Mount Rainier. Despite previous petrologic and paleomagnetic investigations, the origins of these basalts are poorly understood. It is uncertain whether they erupted in situ or were transported to their present location by tectonic processes. It is possible that these lavas were derived from the same magma source as a sequence of flows in the Crescent Formation on the Olympic Peninsula, as both erupted between 45 and 50 million years ago and have similar chemical compositions. A new paleomagnetic analysis of the …

A Petrologic Study Of The Teanaway Basalt: Eocene Slab Window Volcanism In Central Wa, Liz Roepke

Summer Research

The Teanaway Basalt (TB) includes subaerial basalt to andesite flows, mafic to felsic tuffs, and rhyolite domes in the Central Cascades of Washington State. These volcanics overlie the extensive ~47 Ma Teanaway Dike Swarm (TDS) that cuts the underlying Swauk Formation. Samples were collected from 3 main localities: Easton Ridge (ER) in the west, Liberty Ridge (LR) in the east, and the Middle Fork of the Teanaway River (MF) in the center.

The bimodal TB consists predominantly of basaltic andesite and andesite (45.3–63.1 wt% SiO₂) with subordinate rhyolite (75.9–79.4 wt% SiO₂). The mafic rocks classify as …