The Deschutes Formation ranges in age from approximately 7.5 to 4 million years old and consists of volcanic deposits and associated sediments that were predominately sourced from the east flank of ancestral High Cascades. While the Deschutes Formation is present over a large portion of the upper and middle Deschutes Basin in the greater Bend area, to the south it is buried under younger volcanic deposits sourced from the Cascades Range to the west and Newberry Volcano to the south. North of Bend the Deschutes Formation comprises much of the surface geology and is especially well exposed in the canyons of the Deschutes and Crooked Rivers and Whychus Creek. The Deschutes Formation is of particular interest because, not only is it the best way to understand the evolution of the ancestral, High Cascades, but it serves as the major groundwater aquifer in the area.
This field trip will visit a section of the Deschutes River near its confluence with Whychus Creek that is representative of the range of lithologies that make up the Deschutes Formation and its transition from being dominated by volcanic rocks to the west and transitioning to a much greater sedimentary composition to the east. It features exposures of the Deschutes Formation, intra-canyon basalts, baked paleosols, sedimentary features, wild flowers and great views. This will be a good introduction to those who are not familiar with the Deschutes Formation or these outcrops, and for those who are, this is a good chance to become reacquainted and engage in some lively geo-discussions.
This field trip is suitable for all levels of background in geology. Scout Camp Loop trail is a challenging (steep and rocky) 2.2 mile hike with about 500’ of elevation loss/ gain. This trip is led by Derek Loeb and is limited to 12 participants.
Central Oregon Geoscience Society
P.O. Box 2154, Bend, Oregon 97709