Stillwater Complex, Montana; rock succession, metamorphism and structure of the complex and adjacent rocks

Abstract

Along the northern border of the Beartooth Mountains in Stillwater, Sweetgrass, and Park Counties, Mont., a terrane of Precambrian rocks overlain by Paleozoic, Mesozoic, and Cenozoic sedimentary rocks contains the differentiated stratiform ultramafic and mafic Stillwater Complex. In addition to the complex, several groups of Precambrian rocks are distinguished by mineralogic, petrologic, chemical, structural, and age criteria as follows: