Late Quaternary stream incision and uplift in the forearc of the Cascadia subduction zone, western Oregon
- 10 October 1995
- journal article
- Published by American Geophysical Union (AGU) in Journal of Geophysical Research
- Vol. 100 (B10) , 20193-20210
- https://doi.org/10.1029/95jb01684
Abstract
Documentation of a latest Pleistocene/earliest Holocene episode of strath formation and fluvial aggradation in the Oregon Coast Range provides a datum from which long‐term bedrock stream incision rates are determined. Variations in long‐term incision rates probably reflect cumulative differential uplift in the forearc of the Cascadia subduction zone, although factors such as bedrock and climatic controls and isostatic adjustments to erosion obscure the precise relationship between surface uplift and stream incision. Patterns of differential incision are most striking near the latitude of Newport, where a steep gradient divides a region of higher rates (∼0.6–0.9 mm/yr) in the northern Coast Range from a region of lower rates (∼0.1–0.3 mm/yr) in the central Coast Range. The steep incision gradient is nearly coincident with abrupt changes in marine terrace (∼80–125 kyr) uplift rates, the locations of Quaternary faults, and the southern flank of a saddle of low historic (∼40–70 years) uplift. The exact causes of these variable patterns of incision/uplift are unknown. Analogies with uplift patterns in other subduction zones and comparisons with other neotectonic data in the region indicate that patterns of differential incision probably are caused by variations in permanent strain accumulation along the Cascadia subduction zone. Such variations may be related to differences in seismic moment release during individual earthquakes, to changes in plate geometry or rates of wedge accretion, to segmentation of earthquake ruptures, and/or to deformation on active structures in the North American plate and accretionary wedge.Keywords
This publication has 70 references indexed in Scilit:
- Topographic form of the Coast Ranges of the Cascadia Margin in relation to coastal uplift rates and plate subductionJournal of Geophysical Research, 1994
- Controls on bedrock channel incision along nahal paran, IsraelEarth Surface Processes and Landforms, 1994
- Episodic tectonic subsidence of Late Holocene salt marshes, northern Oregon Central Cascadia MarginTectonics, 1990
- Holocene paleoseismicity in the fold and thrust belt of the Hikurangi subduction zone, eastern North Island, New ZealandTectonophysics, 1989
- Subducting seamounts and deformation of overriding forearc wedges around JapanTectonophysics, 1989
- Tomographic image of the Juan de Fuca Plate beneath Washington and western Oregon using teleseismic P‐wave travel timesGeophysical Research Letters, 1988
- Seismicity and volcanism in the Pacific Northwest: Evidence for the segmentation of the Juan De Fuca PlateGeophysical Research Letters, 1985
- Refinement of a technique for determining rock mass strength for geomorphological purposesEarth Surface Processes and Landforms, 1984
- Source mechanisms and tectonic significance of historical earthquakes along the nankai trough, JapanTectonophysics, 1975
- The General Case of Progressive Fault Displacement of Flights of Degradational TerracesNew Zealand Journal of Geology and Geophysics, 1964