Geology Commons^™

The Influence Of Reintroduced Beavers On Sediment Processes In Post-Wildfire Headwater Streams, Methow River, Wa, Amanda Foster

Summer Research

Washington State has experienced increasingly frequent, and intense wildfire activity. For example, the largest fires on record for Okanogan County have occurred in the past five years, and this region includes the Methow River (MR), a main tributary to the Columbia River from the North Cascades. The MR is also the site of an ongoing beaver reintroduction program, that has transplanted over 300 “problem beavers” to headwater streams over the past decade. Historically beavers were abundant in the area, but populations were decimated by fur trapping in the 1800’s. Previous work documented how dam building by reintroduced beavers can rapidly …

Petrology Of The Earliest Cascade Volcanic Units In Washington: The Northcraft, Tukwila, And Rattlesnake Mountain Formations And Implications For The Evolution Of The Cascade Arc, Louisa Cryan, Jeffrey H. Tepper

Summer Research

Cascade arc magmatism began ~45 million years ago, following the reconfiguration of the Farallon-North American subduction zone. This project seeks to classify the path of magmatism throughout the history of the Cascade arc, as well as categorize the earliest expressions of the Cascade arc. Three volcanic units, the Northcraft Formation (NF), Tukwila Formation (TF), and Rattlesnake Mountain Formation (RM) will serve as examples of the earliest Cascades-related lavas. Their categorization by field setting, geochemical characteristics, isotopic data, and age will create a better understanding of how Cascades magmatism began and developed over time.

Analysis has shown these units to contain …

Magnetic Exploration Of The Crescent Formation, Washington: The Search For A Hidden Fault Near Dusk Point, Samuel G. Furmanski

Summer Research

The mafic rocks of the Olympic Peninsula, Washington, are part of an accreted terrane known as Siletzia which experienced transpressional stresses as far as 50 Ma ago in the early Eocene. The Peninsula has an accretion-thrust marine sedimentary interior and a mafic volcanic periphery juxtaposed along the Hurricane Ridge fault; a terrane-scale thrust fault. The mafic Crescent Formation (CF) can be subdivided into two units: The Lower Crescent member (LC) and the Upper Crescent member (UC) as defined by Tabor and Cady (1978). The LC consists of submarine basalt flows that have composition similar to mid-oceanic ridges with zircon fission-track …

Investigating Cascade Magmatism Through Dating And Chemical Analysis Of The Hatchet Mountain And Pe Ell Formations, Sw Wa, Robyn Organ, Jeffery Tepper, Wesely Von Dassow, Tabor Reedy

Summer Research

Modern Cascade arc magmatism began ~45 Ma, shortly after accretion of the Siletzia terrane culminated at ~50 Ma. The earliest expressions of this magmatism are several petrologically-diverse volcanic units in SW Washington including: (1) the Goble Volcanics (GV) / Hatchet Mountain Formation (HM), (2) the Pe Ell Formation (PE), and (3) scattered exposures of unnamed basalts (UB). These rocks, all dominantly subaerial lavas, occur west of the modern arc where they are interbedded with marine and deltaic sedimentary units, suggesting eruption in a forearc or volcanic front setting. Goals of this study are: (1) to characterize the elemental and Sr-Nd …

Petrology Of The Eocene Goble Volcanics, Southwest Washington: An Early Phase Of The Cascade Arc, Clara Phipps, Jeffrey H. Tepper

Summer Research

The Eocene Goble Volcanics (GV), comprised of >1000 km² of subaerial lavas and tuffs, are one of the most voluminous igneous formations in SW WA. Whole rock K-Ar ages of 45 to 32 Ma (Beck and Burr, 1979) suggest these rocks are an early expression of the Cascade arc, but their location is anomalous, lying between oceanic Crescent Fm basalts of the Siltezia terrane to the west and younger arc rocks to the east. The goals of this research are to determine the chemical and Sr-Nd isotopic traits of the GV and better establish the tectonic setting in which …