Date of Award:

1969

Document Type:

Thesis

Degree Name:

Master of Science (MS)

Department:

Geology

Advisor/Chair:

Raymond L. Kerns, Jr.

Abstract

Bear Lake is located in southeastern Idaho and north-central Utah. The lake has a maximum altitude of 5923 feet and an area of approximately 110 square miles. Surrounding the lake are carbonates, shales, and sandstones of lower Paleozoic through middle Mesozoic ages. The many streams and springs that originate in these rocks are probably the main contributors to the chemistry of the lake. Water from Bear River, which flows into the north end of the lake, also contributes to its chemistry. Quartz, aragonite, dolomite, calcite and clay minerals are the main minerals in the lake-bottom sediments. Quartz is generally the dominant mineral in shallow, shoreline areas, whereas aragonite is generally the dominant mineral in deep water. Dolomite occurs in patches near the shoreline along the west and south sides, whereas calcite is fairly evenly distributed throughout the lake. Grains of quartz are detrital in origin. Grains of dolomite and calcite are detrital in origin. Mud-sized aragonite is a primary precipitate that forms pseudoolites around detrital sand grains and lumps of mud-sized particles. The solubility products of aragonite, calcite, and dolomite all are exceeded in the lake water, which, therefore, is supersaturated with respect to all three. Aragonite is more soluble than calcite in water, but chemical and mineral analyses show that mud-sized aragonite is precipitating directly from solutions in Bear Lake, whereas calcite apparently is not. Other workers have attributed the preferential precipitation of aragonite to the inhibition of calcite nucleation in the presence of a high Mg++/Ca++ ratio, a condition present in Bear Lake. Mud-sized calcite and dolomite may be forming syngenetically in the lake sediments as a result of inversion of aragonite to calcite and subsequent replacement of calcite to dolomite, or may be entirely detrital in origin.

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