First Advisor

Evanoff, Emmet

Degree Name

Master of Arts

Document Type

Thesis

Date Created

5-2019

Department

College of Natural and Health Sciences, Earth and Atmospheric Sciences, EAS Student Work

Abstract

The White River Group in Badlands National Park is significant because it contains abundant mammal fossils. Many of these fossils are unique to the Great Plains and one of the major challenges has been to learn where these fossils fit in the geologic global time scale. Paleomagnetic studies have been instrumental in correlating and dating these faunas. The purpose of this study is to look at the specific magnetic mineralogy for a complete stratigraphic column of the lower Poleslide Member of the Brule Formation at Cedar Pass. This study attempts to determine what minerals provide the paleomagnetic remanence in these rocks. This study used three techniques to determine the quantities and kinds of magnetic minerals in the samples and determine if there are any significant patterns in the amounts of magnetic minerals or in the types of magnetic minerals. The magnetic minerals were removed from crushed rock samples with a strong bar magnet. Portions of the separated magnetic minerals were treated with hydrochloric acid (HCl), to separate the easily dissolved magnetite grains from other resistant magnetic materials. Four samples were analyzed with a scanning electron microscope to determine the composition of the magnetic minerals. These techniques were used to determine if there are significant patterns in the amounts and kinds of magnetic materials through the stratigraphic section. The overall quantities of magnetic minerals in the rock samples ranted from 0.05% to 0.63% of the total rock mass. The most significant results show that the quantities of HCl resistant minerals changes at 31.5 meters above the base of the stratigraphic section. Below this level, acid-resistant magnetic minerals occur in low concentrations in many of the treated samples. Above the 31.5 m level, these acidresistant minerals are essentially absent, occurring in only trace amounts ( total rock mass). The SEM analysis is not conclusive in confidently identifying the specific minerals. However, the evidence suggests the magnetic minerals contain magnetite, titanomagnitite or hemo-ilmenite and perhaps ulv ӧspinel.

Extent

58 pages

Local Identifiers

kipfThesis2019.pdf

Rights Statement

Copyright is held by the author.

Digital Origin

Born digital

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