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Date Permissions Signed

3-8-2021

Date of Award

Winter 2021

Document Type

Masters Thesis

Department or Program Affiliation

WWU Department of Geology

Degree Name

Master of Science (MS)

Department

Geology

First Advisor

Dahl, Robyn

Second Advisor

Clark, Douglas H., 1961-

Third Advisor

Hatch, Marco B.A.

Abstract

The ecologic response of marine invertebrates during collapse of the Cordilleran Ice-sheet through the Late Pleistocene has been insufficiently studied across the lowlands of northwestern Washington State and southern Fraser Valley, British Columbia. Assessment of the response of these nearshore marine assemblages to climatic shifts will improve our understanding of closely related modern taxa in analogous climate-stressed conditions. If we understand the former vulnerability of related genera, meaningful predictions may thus be provided for extant taxa in current and future time. In this thesis, I establish a compilation dataset of all relevant specimens collected within the Salish Sea and Puget lowland regions that integrate newly recovered specimens in tandem with studies completed over the last century.

Prior research applied marine fossil occurrences to track, interpret, and model ice-sheet dynamics, often overlooking the ecological information the fossils contain. This investigation utilizes micro- and macro-invertebrate assemblage measures and linear ecologic regressions to capture paleoenvironments, identify meaningful relationships among assemblages and sedimentary facies, and better refine interpretation of depositional sequences. Using multivariate quantitative analyses, my data reveal an overall disparity in species diversity, evenness, and richness among a generally northern and southern assemblage in both micro- and macrofaunas. South of Bellingham, WA, assemblages are diverse and dominated by shallow-water taxa capable of inhabiting variable salinities ranging from brackish to normal (approximately 20‰ to 30‰). Environments represent salinity-reduced, likely riverine and marine water mixing zones where pulses (fluxes of food and sediment) were discharged into the region. North of Bellingham assemblages exhibit low overall diversity of relatively deeper water taxa inhabiting near normal marine salinities (>30‰). Substrates become finer-grained and include larger occurrences of Arctic species. The study concludes that most genera that colonized the Salish Sea and Puget lowlands during glacial collapse originated from populations already inhabiting the region, alongside limited arctic faunas that had earlier migrated south with glaciation following their appropriate temperature zones.

Type

Text

Keywords

Bivalve, Mollusk, Foraminifera, Paleoecology, Taphonomy, Sedimentary facies, Crustal movement, Multivariate analysis

Publisher

Western Washington University

OCLC Number

1242064885

Subject – LCSH

Mollusks--Climate factors--Salish Sea (B.C. and Wash.); Foraminifera--Salish Sea (B.C. and Wash.)--Geographical distribution; Paleoecology--Pleistocene; Facies (Geology)--Salish Sea (B.C. and Wash.); Sedimentation and deposition--Salish Sea (B.C. and Wash.); Glaciology--Salish Sea (B.C. and Wash.)

Geographic Coverage

Salish Sea (B.C. and Wash.)

Format

application/pdf

Genre/Form

masters theses

Language

English

Rights

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

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