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Petrology And Mineralogy Of Quaternary Basalts, Gem Valley And Adjacent Bear River Range, Southeastern Idaho, William D. Perkins
Petrology And Mineralogy Of Quaternary Basalts, Gem Valley And Adjacent Bear River Range, Southeastern Idaho, William D. Perkins
All Graduate Theses and Dissertations, Spring 1920 to Summer 2023
Quaternary basalts of Gem Valley, Idaho, are present as valley fill (Group 1) and as well defined flows in the Bear River Range (Group 2) east of Gem Valley. Minerals present in both groups of basalts include olivine (Fo73 -Fo39), augite (Wo41 En39 Fs20), plagioclase (An75 -An40), and Fe-Ti oxides. Coexisting pairs of magnetite and ilmenite, and olivine and clinopyroxene in several samples indicate temperatures of crystallization from 958°c to 1167°c. The Group 2 basalts exhibit a cumulate texture with abundant large (2 cm) phenocrysts of plagioclase.
Chemically, the Gem …
Structural Geology Of The Northern Part Of Oxford Quadrangle, Idaho, Jerrold N. Mayer
Structural Geology Of The Northern Part Of Oxford Quadrangle, Idaho, Jerrold N. Mayer
All Graduate Theses and Dissertations, Spring 1920 to Summer 2023
The northern part of the Oxford Quadrangle, Idaho, includes parts of the Bannock Range to the west and the Portneuf Range to the east. These ranges are separated by Marsh Valley to the north and Cache Valley to the south. Red Rock Pass, the outlet of glacial Lake Bonneville, divides the two valleys. The mapped area is north of Preston, Idaho, and south of Downey, Idaho. The north-south dimension of the mapped area is 5.2 miles and the east-west dimension is 6.4 miles.
The stratigraphic units, within the mapped area, are Precambrian, Paleozoic, and Cenozic in age. The oldest rock …