Publication Date

1976

Document Type

Dissertation/Thesis

First Advisor

Odom, J. Edgar

Degree Name

M.S. (Master of Science)

Legacy Department

Department of Geology

LCSH

Mineralogy--Minnesota; Petrology--Minnesota

Abstract

The lithic and mineralogic properties of the Cambrian strata in the subsurface of southeastern Minnesota were investigated to define regional and stratigraphic variations. This sequence of sandstones and dolomites was deposited in an embayment characterized by shallow water conditions. The sediments represent primarily transgressive deposits, although the results of this study indicate that regressive deposits are also present in both the Eau Claire and Franconia Formations. The basal Cambrian formation, the Mt. Simon, consists primarily of medium-and fine-grained sandstone, but its texture is highly variable locally. The Eau Claire Formation, which overlies the Mt. Simon, consists primarily of fine-grained sandstone. It is divisible into five lithic units, four of which are traceable throughout most of the area. The fifth unit appears to occur only near the Transcontinental Arch. The medium- and fine-grained Ironton and Galesville Sandstones are present throughout the area. These sandstones become primarily fine-grained in the southern part of the area. The Franconia Sandstone in the northern parts of the area contain three distinct members--the Birkmose, Tomah and Reno, but in the southern part the Tomah Member thickens and completely replaces the Reno. The St. Lawrence Formation, which overlies the Franconia, is predominately dolomite throughout most of the area, but toward the north and east it contains increasing amounts of siltstone (Lodi). The youngest Cambrian stratigraphic unit, the Jordan Sandstone, is present throughout the area but insufficient samples were available to differentiate it into members. The essential minerals composing the Cambrian sediments are quartz, feldspar, glauconite and dolomite. Feldspar content was found to be related to grain size, increasing with decreasing size. Feldspar, glauconite and dolomite contents were used to define regional and stratigraphic mineralogic variations (mineral facies). The mineral facies recognized include quartz, feldspathic and highly feldspathic arenites; glauconitic, feldspathic arenites; highly feldspathic siltstones; dolomites; and sandy dolomites. The regional and stratigraphic distributions of these mineral facies reflect the influence of the depositional environments of sediment type and grain size.

Comments

Includes bibliographical references (pages [51]-52)

Extent

78 pages

Language

eng

Publisher

Northern Illinois University

Rights Statement

In Copyright

Rights Statement 2

NIU theses are protected by copyright. They may be viewed from Huskie Commons for any purpose, but reproduction or distribution in any format is prohibited without the written permission of the authors.

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