Geology of the Northern Mineral Range, Millard and Beaver Counties, Utah

The primary purpose of this investigation was the mapping of the northern part of the Mineral Range on a scale of approximately 1:20,000, and the preparation of a report on the structure, stratigraphy, igneous and metamorphic rocks which are present. An attempt has also been made to reconstruct the geologic history of the area. The geology of the Northern Mineral Range, as it will be referred to in this report, is complex. This is chiefly because: (1) almost all of the sedimentary rocks in the area probably belong to the same stratigraphic system and were found to be, in general, unfossiliferous; (2) the area lies within a belt of thrusting; (3) the Northern Mineral Range has been the site of igneous activity on a relatively large scale; and (4) normal faults and local areas of metamorphism are abundant. As a result, conclusive geologic evidence as to the age and complete nature of some tectonic features has not been discovered by the writer. This has necessitated, in certain instances, the formulation of hypotheses rather than definite conclusions. The rocks are described with regard to: (1) general physiographic expression and position; (2) petrologic and petrographic characteristics; (3) age and correlation; (4) origin; (5) relation to other rocks; and (6) alteration. This investigation does not represent the final word on the geology of the Northern Mineral Range. Much research remains to be done, and as will be shown later, several interesting field and laboratory problems are available for academic study.