Date of Award

1970

Document Type

Dissertation

Degree Name

Doctor of Philosophy (PhD)

Department

Geology

First Advisor

L. Clayton

Abstract

Rolette County contains approximately 942 square miles in north central North Dakota (Tps. 159-164 N., Rs. 69-73 W.) adjacent to the Canadian border. It includes the southeastern part of the Turtle Mountains and part of the glacial Lake Souris basin. Basic lithologies recognized in the surface sediments were bedded clay, silt, sand, and gravel; and three types of non-bedded diamicton. These were combined and, with bedding characteristics and organic content, formed 15 practical field mapping units. Geologically significant scarps and hill slopes were also mapped. The data collected is shown at a scale of 1 inch to 2 miles. The lithologic data are combined to form 26 interpretive, genetic geologic units shown at a scale of 1 inch to 4 miles. Genetic types recognized are (1) wind-blown sediment (loess), (2) lake sediment (modern lake and pond sediment; sediment deposited in ice-marginal glacial Lake Souris having strandline features preserved at elevations of approximately 1,600, 1,570, 1,550, 1,525, and 1,510 feet; and lake sediment deposited during the last deglaciation both on solid ground and on glacial ice), (3) stream sediment {modern stream sediment and sediment deposited during the last deglaciation both on solid ground and on stagnant glacial ice), and {4) mudflow sediment with some glacier sediment which together are commonly called "till” (diamicton related to ice xiii that advanced southward across the Turtle Mountain a containing shale, sandstone, and lignite in the stony fraction; diamicton in the eastern and northern part of the county deposited by the Leeds lobe and commonly containing shale but rarely containing sandsto~'1e and lignite in the stony fraction; and diamicton that is dominantly sand deposited by the eastward-moving Souris River lobe south of the Turtle Mountains). Prior to the last glacial advance a north-south-trending valley extended part way across the Turtle Mountains and drainage was generally southeasterly across the county. Stagnation of the last glacial advance occurred before 13,000 B.P. over the topographic high of the Turtle Mountains, where compressive flow conditions caused an uriusual thickness of dirty ice. An insulating blanket of superglacial sediment quickly formed and retarded melting. The ice-free Rolette meltwater basin formed south of the Turtle Mountains and was overridden by a re advance of the eastward-moving Souris River lobe approximately 12,900 or 13,000 B. P., after which all the ice in Rolette County stagnated. Melting was rapid except in the Turtle Mountains, and most stagnant ice melted in a few hundred years. The well-insulated buried ice over the Turtle Mountains and other, smaller, buried blocks may have taken as much as 3,000 years to melt, resulting in much topographic inversion and mudflow activity. Glacial Lake Souris existed, at various elevations, between approximately 12,900 and 12,000 B. P. Between approximately 13,000 and 10,500 B.P. the climate was more moist than today, the county was covered with spruce forest, and many lakes and ponds existed. Between approximately 10,500 and 8,500 B.P. the climate was much like it is today, many lakes turned into temporary ponds, and forest cover was restricted to the Turtle Mountains. Between approximately 8,500 and 4,500 B.P. the climate was effectively more arid tr.an today, most lakes dried up, and grassland replaced forest over most of the Turtle Mountains. The present climate was established about 4,500 or 4,000 B .P. The basic lithologic data are combined with information. Provided by others to form user-oriented maps designed to aid urban and agricultural planners. They show ground-water resources, sand and gravel resources, near-surface permeability, and construction capabili ties at a scale of l inch to 4 miles.

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Deal Plates.zip (257840 kB)
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