Eroding Cascadia— Sediment and solute transport and landscape denudation in western Oregon and northwestern California
Riverine measurements of sediment and solute transport give empirical basin-scale estimates of bed-load, suspended-sediment, and silicate-solute fluxes for 100,000 km2 of northwestern California and western Oregon. This spatially explicit sediment budget shows the multifaceted control of geology and physiography on the rates and processes of fluvial denudation. Bed-load transport is greatest for steep basins, particularly in areas underlain by the accreted Klamath terrane. Bed-load flux commonly decreases downstream as clasts convert to suspended load by breakage and attrition, particularly for softer rock types. Suspended load correlates strongly with lithology, basin slope, precipitation, and wildfire disturbance. It is highest in steep regions of soft rocks, and our estimates suggest that much of the suspended load is derived from bed-load comminution. Dissolution, measured by basin-scale silicate-solute yield, constitutes a third of regional landscape denudation. Solute yield correlates with precipitation and is proportionally greatest in low-gradient and wet basins and for high parts of the Cascade Range, where undissected Quaternary volcanic rocks soak in 2−3 m of annual precipitation. Combined, these estimates provide basin-scale erosion rates ranging from ∼50 t ∙ km−2 ∙ yr−1 (approximately equivalent to 0.02 mm ∙ yr−1) for low-gradient basins such as the Willamette River to ∼500 t ∙ km−2 ∙ yr−1 (∼0.2 mm ∙ yr−1) for steep coastal drainages. The denudation rates determined here from modern measurements are less than those estimated by longer-term geologic assessments, suggesting episodic disturbances such as fire, flood, seismic shaking, and climate change significantly add to long-term landscape denudation.
Citation Information
| Publication Year | 2021 |
|---|---|
| Title | Eroding Cascadia— Sediment and solute transport and landscape denudation in western Oregon and northwestern California |
| DOI | 10.1130/B35710.1 |
| Authors | Jim E. O'Connor, Joseph F. Mangano, Daniel R. Wise, Joshua R. Roering |
| Publication Type | Article |
| Publication Subtype | Journal Article |
| Series Title | Geological Society of America Bulletin |
| Index ID | 70217220 |
| Record Source | USGS Publications Warehouse |
| USGS Organization | Geology, Minerals, Energy, and Geophysics Science Center; Oregon Water Science Center |
Related Content
Pacific Northwest Geologic Mapping: Northern Pacific Border, Cascades and Columbia
Related Content
- Science
Pacific Northwest Geologic Mapping: Northern Pacific Border, Cascades and Columbia
The Pacific Northwest is an area created by active and complex geological processes. On its path to the Pacific Ocean, the Columbia River slices through a chain of active volcanoes located along the western margin of the U.S. in Washington, Oregon, and northern California. These volcanoes rest above the active Cascadia subduction zone, which is the boundary where the oceanic tectonic plate dives... - Connect