Tectonic History of the Coos Bay Basin and its Relationship to Pacific Northwest ‘Siletzia’ Tectonics

Laird Thompson

University of Utah

5:30 pm social hour

7:00 pm presentation

Laird Thompson will explore the tectonic history of the Coos Bay Basin in southwestern Oregon and what it can tell us about the larger tectonic history of Oregon and the Pacific Northwest. The Coos Bay Basin overlies the southwestern margin of ‘Siletzia’, an accreted mass of marine basalt that forms the basement rock beneath western Oregon and Washington. Fault and fracture patterns within the Coos Bay Basin are visible in rock outcrops, lidar, gravity, and geologic maps. These patterns record four phases of tectonic deformation associated with the clockwise rotation of Oregon and the northward transport of Siletzia. This talk will build on material presented by Ray Wells in his visit to COGS in May of 2018.