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Date Permissions Signed

2-28-2018

Date of Award

Spring 2008

Document Type

Masters Thesis

Degree Name

Master of Science (MS)

Department

Geology

First Advisor

Linneman, Scott

Second Advisor

Suczek, Christopher A., 1942-2014

Third Advisor

Housen, Bernard Arthur

Abstract

Sedimentary rocks found in the 4.5 x 8 km Kulshan caldera of the Mount Baker volcanic field in the North Cascades, WA, indicate that the post-collapse basin hosted a lacustrine environment shortly after the initial collapse at 1.149 Ma (Hildreth, 1996). The sedimentary rocks of the 14 Goat area in Kulshan caldera are well-preserved in 124 meters of stratigraphic exposure. Blocks of wall rock debris in the lower stratigraphy show instability in the caldera wall. Intermediate and late stages are mainly turbidites composed primarily of sediments derived from extra-caldera ignimbrite. From these 1 interpret the 14 Goat area of Kulshan to have been a steep and deep depositional basin for most of its history. Additional sedimentary structures found in Kulshan caldera reveal a complex environmental history. Trough cross-bedding within a well sorted sandstone indicates channelized flow. Clastic dikes resulted from the overburdening of wet sediments. Dropstones found throughout the stratigraphy indicate an active ice field. Outside the stratigraphic section but within the 14 Goat area oscillation ripples indicate shallow water and raindrop imprints show drying. Paleomagnetic analysis of 12 sites spanning the entire stratigraphic column failed to show that any magnetic transition was recorded in the Kulshan sediments. Anisotropy of magnetic susceptibility results confirm that grain settling from quiet water produced the most prominent magnetic fabric and confirm secondary alteration was likely the cause of scatter in the remanent magnetization signal. A conservative estimate for the duration of the lacustrine environment at Kulshan caldera is 157 ka leading to a minimum rate of sedimentation of 79 cm/ka. A shorter estimate suggests duration of 22 ka and rate of sedimentation of 560 cm/ka. The sedimentary environments of Kulshan caldera are similar to other calderas with post-collapse depositional records. Kulshan caldera compares favorably to depositional models for small calderas (less than 10 km).

Type

Text

Keywords

Kulshan caldera, Mount Baker volcanic field, Lacustrine environment

Publisher

Western Washington University

OCLC Number

1030748593

Geographic Coverage

Baker, Mount (Wash.)

Genre/Form

masters theses

Language

English

Rights

Copying of this thesis in whole or in part is allowable only for scholarly purposes. It is understood, however, that any copying or publication of this thesis for commercial purposes, or for financial gain, shall not be allowed without the author's written permission.

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