Geology of the Central and Eastern Snake River Plain Part I:: Bimodal Volcanics

The Central and Eastern Snake River Plain is a bimodal volcanic province formed by migration of the North American Plate westward over the Yellowstone Hot Spot. Volcanic units consist of rhyolitic flows and ash fall deposits with basaltic flows originating from eruptive and volcanic centers mainly known as the Bruneau-Jarbidge, Juniper Mountain-Owyhee, Owyhee-Humboldt, and Twin Falls volcanic centers.

Chapter 1 presents the Central Snake River Plain volcanic province introducing sample locations where zircon populations occur from the Archaen to the Pleistocene periods. Modern stream signatures and drainage development are discussed. Chapter 2 addresses Snake River Plain rhyolites presenting volcanic progression, tectonic associations, and petrology. Chapter 3 presents details on Miocene tuff deposits belonging to the McMullen Creek Tuff.

Chapter 4 discusses the transition from ash flow to voluminous lava flow activity in the Bruneau-Jarbidge eruptive center.

Chapter 5 presents pre- and post- Juniper Mountain Volcanic Center conditions of rhyolitic, tuffaceous, and basaltic compositions.

Chapter 6 presents basaltic units of the Bruneau-Jarbidge and Twin Falls regional areas.

Chapter 7 begins the Eastern Snake River Plain discussion providing an overview of the provincial geology.

Chapter 8 discusses Eastern Snake River Plain extension and subsidence including basin and range faulting and basin infilling.

Chapter 9 presents Quaternary evolution of tholeiitic basalt eruptive centers. This chapter concludes Part I of a two part series on the ESRP.

Part II presents a field excursion leading to Craters of the Moon National Monument, through the national monument,and introduces volcanics associated with the Great Rift of Idaho.