Physical Sciences and Mathematics Commons^™

Petrology Of The Cenozoic Phonolites And Related Rocks Of The Houston Creek Area, Bear Lodge Mountains, Wyoming, Frederick S. O’Toole

Theses and Dissertations

The purpose of this study was to map and study the characteristics and origin of the Cenozoic phonolites and related rocks of the Houston Creek area, located on the southwestern flank of the Bear Lodge Mountains, 10 km northwest of Sundance, Wyoming. Mapping was conducted on a 2 1:10,000 scale over a 16 km area. Microprobe, optical, and x-ray diffraction procedures were employed to observe and describe petrographic and chemical characteristics of the rocks.

The Cenozoic igneous rocks of the Houston Creek area are classified as phonolite, phonolite porphyry, trachyte porphyry, sodalite-bearing phonolite and altered felsite. These hypabyssal rock types …

Petrology Of The Cenozoic Igneous Rocks Of The Lytle Creek Area, Bear Lodge Mountains, Wyoming, Stanely F. White

Theses and Dissertations

The purpose of this study was to map and study the petrology of the Cenozoic igneous rocks that crop out in the Lytle Creek area located in the southwestern Bear Lodge Mountains of northeastern Wyoming. Petro graphic and chemical data is used to interpret the Cenozoic phonolite trachyte rock association.

Cenozoic igneous activity in the Lytle Creek area appears to have been a response to the Laramide orogeny 80-40 m.y. B.P. The majority of the rocks were emplaced as laccoliths and sills at the Pahasapa Formation-Minnelusa Formation contact or at the Spearfish Formation Sundance Formation contact. Porphyritic volcanic textures are …

The Late Cenozoic Geology Of West-Central Minnesota From Moorhead To Park Rapids, Roderic L. Perkins

Theses and Dissertations

Based on lithostratigraphic and geomorphic information, the Quaternary history of an area bounded by the Red River of the North, 95°00' west longitude, 47°00' and 46°45' north latitude in west central Minnesota, includes seven geologic episodes:

Glacial advances and retreats over all or part of the study area occurred during the first six geologic episodes. The glaciers advanced either southward across northern Minnesota, entering the study area from the northeast; or across eastern North Dakota and southwestern Manitoba, entering the study area from the northwest. As a result of these glacial events the sediment of Unit A, Sebeka Formation, New …

Latest Cenozoic Stratigraphy Of Lake Sakakawea Area, Northeast Mercer County, North Dakota, Donald Kieth Sackreiter

Theses and Dissertations

The latest Cenozoic in northeast Mercer County, North Dakota, is represented by five formations. They are, from bottom to top: the Charging Eagle Formation, the Medicine Hill Formation, the Snow School Formation, the Coteau Formation, and the Oahe Formation.

The Charging Eagle Formation is mainly fluvial sediment. Most of the sediment was derived from the west with only minor amounts from the northeast. It contains the first evidence of glaciation in the area.

The lower Medicine Hill Formation is mainly sediment deposited by a northeast-flowing ancestor of the Missouri River and by melt-water streams. The upp.er Medicine Hill Formation is …