Central Oregon Geology: The Brothers Fault Zone, High Lava Plains, & the John Day Country

Central Oregon consists of the Brothers Fault Zone which separates the Northwest Basin & Range from the High Lava Plains to the north. The High Lava Plains lies south of John Day Country. This book attempts to compile geological features and history of the geomorphic provinces that compose Central Oregon.Chapter 1 presents an introduction to the Brothers Fault Zone. Chapter 2 presents the High Lava Plains characteristic features from physiography to geological overview and settings including Pleistocene lakes, the Harney Basin, and potential geothermal resources. Chapter 3 addresses bimodal volcanism of the High Lava Plains. Chapter 4 presents geological features of the High Lava Plains. Chapter 5 presents an introduction to John Day Country offering a road log for 19 sites from Spray through Kimberly, Monument, Hamilton, Long Creek, Fox Valley, and the Strawberry Range. Chapter 6 begins with the geologic framework of the Clarno Unit in the John Day Fossil Beds National Monument. This chapter features the geologic setting, physiography, and litho-stratigraphic units of the Clarno Formation and John Day Formation. The chapter also presents structural geology, petrology, and depositional settings in both formations. Chapter 7 discusses the geology of the Upper John Day Formation Beds and members, offering regional correlative significance of the upper units. Chapter 8 begins the discussion of the John Day Fossil Beds National Monument with an overview and discussion of Paleogene and Neogene global climate change. Both Clarno and John Day formations are summarized. An introduction to paleo-sols is included for the major formations. Geological features are presented at the end of the chapter. Chapter 9 summarizes the geological history of the national monument focusing on global greenhouse to icehouse events in the Tertiary epochs. Chapter 10 provides a field tour of the national monument and surrounding region focusing on the Crooked River and Wildcat Mountain calderas. Chapter 11 closes the book with the continuation of the field trip from the Ochoco Summit eastward to the Painted Hills and Sheep Rock Units. Read more