Abstract

Fluviolacustrine deposits of middle Miocene age occur on the western margins of the Amargosa Valley, in the central Basin and Range. These deposits contain the earliest pupfish (Cyprinodon) reported from the fossil record. National Park collections contain specimens of pupfish fossils, interpreted as possibly Pliocene; however the exact collection location and stratigraphic horizon was not known. Therefore, the geographic extent of the fossil locality and geologic age of these specimens were uncertain. Recently, these collection sites were relocated and additional sites were discovered. Ar-Ar dating of interbedded tuffs established the first appearance datum of pupfish at 14.79 Ma and extended their presence to 10.17 Ma. Analysis of sedimentary facies and petrography indicate a clastic-dominated lacustrine system fed by streams that occasionally prograded into the lacustrine complex. Fluviolacustrine accumulation was interrupted four or more times by deposition of thick volcanic ashes. The middle Miocene was a time of significant development of lacustrine systems during the Basin and Range extension, which probably played a role in the dispersal and speciation of pupfish.

LLU Discipline

Geology

Department

Geology

School

School of Medicine

First Advisor

Kevin E. Nick

Second Advisor

Ana Martinez Ardila

Third Advisor

Ronald Nalin

Fourth Advisor

Torrey Nyborg

Degree Name

Master of Science (MS)

Degree Level

M.S.

Year Degree Awarded

2022

Date (Title Page)

12-2021

Language

English

Library of Congress/MESH Subject Headings

Geology, Stratigraphic—Miocene; Sedimentation and deposition; Lakes—Sedimentation; Fossil fishes; Cyprinodon, Fossil; Petrography; Volcanic ash, tuff, etc.; Geochronometry

Type

Thesis

Page Count

154 p.

Digital Format

PDF

Digital Publisher

Loma Linda University Libraries

Usage Rights

This title appears here courtesy of the author, who has granted Loma Linda University a limited, non-exclusive right to make this publication available to the public. The author retains all other copyrights.

Collection

Loma Linda University Electronic Theses and Dissertations

Collection Website

http://scholarsrepository.llu.edu/etd/

Repository

Loma Linda University. Del E. Webb Memorial Library. University Archives

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Geology Commons

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