Yakima Fold Belt

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The Yakima Fold Belt in the south central part of the US state Washington in the counties Yakima , Kittitas , Klickitat , Benton and Grant , also called Yakima fold-and-thrust belt (German about Yakima fold- thrust belt ), is an area topographical folds that have been lifted up by tectonic compression. It is the approximately 14,000 km² structural-tectonic sub-province of the western Columbia Plateau , which is the result of complex and as yet poorly understood regional tectonics . The folds are associated with geological faults, the seismic risk of which is of particular interest to the nuclear facilities at the Hanford Nuclear Complex (immediately northwest of the Tri-Cities ) and the dams on the Columbia and Snake Rivers .

geography

Lake Keechelus Lake Kachess Lake Cle Elum Cle Elum Ellensburg Quincy Ephrata Moses Lake Pot Holes Reservoir Othello Yakima Union Gap Wallula Gap Goldendale The Dalles Hood River Tacoma Tri-Cities Mount Rainier Mount Saint Helens Mount Adams Rock Island Dam Wanapum Dam Priest Rapids Dam Ice Harbor Dam McNary Dam John Day Dam The Dalles Dam Bonneville Dam White River Cle Elum Ridge South Cle Elum Ridge Manastash Ridge Umtanum Ridge Boylston Mountains Badger Mountain Beezley Hills Saddle Mountains Frenchman Hills Gable Mountain Cleman Mountain Yakima Ridge Bethel Ridge Cowiche Mountain Sedge Ridge Ahtanum Ridge Rattlesnake Hills Toppenish Ridge Snipes Mountain Horse Heaven Hills Simcoe Mountain Bickleton Ridge Columbia Hills (Washington) Paterson Ridge Red Mountain Olympic-Wallowa Lineament Craton edge Naneum-Hog Ranch Anticline
Relief map showing the mountain ranges of the Yakima Fold Belt in south-central Washington , mainly between Interstate 90 (red line) and the Columbia River (below). The red square in the center is the city of Yakima , the red rectangle at the bottom right the Tri-Cities , the red circles are different cities, the triangles are the volcanoes Mount Rainier , Mount Saint Helens and Mount Adams in the Cascade Range in southern Washington. The purple dashed line marks the approximate location of the Olympic Wallowa Lineament (OWL), which crosses the Columbia River at Wallula Gap (bottom right). The orange dashed line represents the approximate location of the border of the North American craton ( Laurentia ). The relatively flat surface of the central and eastern areas is due to the filling of volcanic rivers of the Columbia Plateau basalt .

The topographical diversity of the Yakima Fold Belt (see relief map) stems from its formation from a layer of lava flow and the sedimentary deposits that generally filled the bumps and leveled the surface of a large part of the Columbia catchment . The extent of these lava flows was limited to the west and north by the ascending Cascade Mountains and the Wenatchee Mountains . The lava flows extend far beyond the area shown in the east, the Yakima Fold Belt not. The northernmost fold shown here (the Frenchman Hills) ends at Potholes Reservoir , another (the Saddle Mountains ) ends just south of it near the small town of Othello (red circle). South of the Tri-Cities, the Wall of Horse Heaven Hills extends a short distance across the Columbia River. The ends of these mountain ranges mark the boundary of a block of continental crust (part of the North American craton represented by the broken orange line) that withstood the tectonic pressure that formed the chains.

The southernmost chain of the Yakima Fold Belt is the Columbia Hills on the north side of the Columbia River. The folding pattern continues with the Dalles-Umatilla syncline just south of the Columbia River and further into Oregon with the Blue Mountains anticline , which runs roughly parallel to the Klamath-Blue Mountain lineament which forms the southeastern border of Siletzia (see geological map below).

The Yakima Fold Belt is also located on the Olympic Wallowa Lineament (OWL), a broad zone of linear topographical features (broken yellow line) from the Olympic Peninsula in northwest Washington to the Wallowa Mountains in northeast Oregon; the orientation and spatial extent of some of the folds of the belt are influenced by it.

geology

Yakima Fold Belt (thin purple lines with black diamonds) in the context of the main regional geological structures. The extent of the Columbia River basalt is in light green. The thickest purple line is the OWL, the thickest orange line corresponds to the border of the Kraton in the relief map above. The Klamath Blue Mountain Lineament (KBML, approximate location, extends to the coast) is the southern limit of the marine basalt of Siletzia . BFZ, EDFZ and MFZ are the Brothers, Eugene Denio and McLaughlin fold zones, respectively.

The central part of the Olympic-Wallowa Lineament, known as the Cle Elum-Wallula Deformation Zone (CLEW), consists of a series of generally east-running, closely spaced asymmetrical anticline mountain ranges and broad synclinal valleys, which in the Miocene are formed by the lava flows of the Columbia River basalt Group and shaped by sediments. In most parts of the Belt, the folds have a northward vergence (the southward vergence of the Columbia Hills is an exception) with steep fold legs typically disturbed by scale-shaped thrusts. The length of the folds ranges from one to a hundred kilometers with wavelengths (between the folds) of a few to twenty kilometers.

A trench lies almost under the entire Yakima Fold Belt and has been subducted since the Eocene ; it continues to sink at a slow rate.

A study of 2011 yielded aeromagnetic , solemn and paläoseismologische evidence for linking the Yakima Fold Belt with the active Puget Sound turmoil .

geodesy

Geodetic studies of the Oregon rotation show that Oregon rotates around a point just south of Lewiston, Idaho , pushing the Yakima Fold Belt together an average of about three millimeters per year and the Pacific coast of Washington by about seven millimeters per year.

Investigations into the movement of the Yakima Fold Belt were undertaken to assess seismic hazards for the Hanford Site .

See also

Individual evidence

  1. ↑ Elizabeth A. Barnett, Brian L. Sherrod, Robert Norris, Douglas Gibbons: Paleoseismology of a newly discovered scarp in the Yakima fold-and-thrust belt, Kittitas County, Washington . In: United States Geological Survey . Scientific Investigations Map 3212, 2013.
  2. ↑ a b c D.J., compiler Lidke: Fault number 562b, Saddle Mountains structures, folds and other faults of the Saddle Mountains . In: Quaternary fault and fold database of the United States: US Geological Survey website . United States Geological Survey . 2002. Retrieved August 19, 2014.
  3. ↑ a b c Stephen P. Reidel, Barton S. Martin, Heather L. Petcovic: Terry W. Swanson (Eds.): The Columbia River flood basalts and the Yakima fold belt - Western Cordillera and Adjacent Areas  (= Geological Society of America Field Guide), Volume 4. Geological Society of America, 2003, ISBN 9780813700045 , p. 91.
  4. ^ Thomas L. Pratt: Large-scale splay faults on a strike-slip fault system: The Yakima Folds, Washington State . In: Geochemistry, Geophysics, Geosystems . November 13, 2012. doi : 10.1029 / 2012GC004405 .
  5. ↑ Some researchers also include structures north of it in the Belt.
  6. ↑ a b Stephen P. Reidel, Karl R. Fecht, Michael C. Hagood, Terry L. Tolan: The Geologic Evolution of the Central Columbia Plateau . In: SP Reidel, PR Hooper (ed.): Volcanism and Tectonism in the Columbia River Flood-Basalt Province , Volume Special Paper 239. Geological Society of America, 1989, ISBN 9780813722399 , pp. 247-264, doi : 10.1130 / SPE239 -p247 : "" The central part of ... [the] Olympic-Wallowa Lineament (OWL) passes through the central Yakima fold belt. This segment of the OWL is referred to as the Cle Elum-Wallula deformed zone (CLEW)… ““
  7. ↑ Stephen P. Reidel: Northwest Geological Society Field Trips in Pacific Northwest Geology: The Geologic Development of the Pasco Basin, South-Central Washington . Northwest Geological Society, 2004. Archived from the original on October 6, 2014 Info: The archive link was automatically inserted and not yet checked. Please check the original and archive link according to the instructions and then remove this notice. (Accessed August 21, 2014). @1@ 2Template: Webachiv / IABot / www.nwgs.org
  8. ↑ Richard J. Blakely, Brian L. Sherrod, Craig S. Weaver, Ray E. Wells, Alan C. Rohay, Elizabeth A. Barnett, Nichole E. Knepprath: Connecting the Yakima fold and thrust belt to active faults in the Puget Lowland , Washington . In: Journal of Geophysical Research: Solid Earth . 116, No. B7, July 28, 2011. doi : 10.1029 / 2010JB008091 .
  9. ^ Ray E. Wells, Richard J. Blakely, Brian L. Sherrod, Craig S. Weaver: The Yakima Fold and Thrust Belt - a paradigm for active shortening in the Columbia embayment from Pasco to the Pacific Ocean . In: American Geophysical Union, Fall Meeting . American Geophysical Union, 2009, abstract S41F-01: ""… folding in the embayment is driven by the clockwise rotation of Oregon about a pole near the OR-WA-ID border, compressing Washington against slow-moving Canada. The folds fan westward from this pole of rotation, and shortening increases to the west to about 7.1 mm / yr between Astoria and Penticton, BC. Shortening across the YFB is about 3 mm / yr and decreases eastward to the Idaho border. ""
  10. ↑ George V. Last, Kelsey Winsor, Stephen D. Unwin: A Summary of Information on the Behavior of the Yakima Fold Belt as a Structural Entity - Topical Report , Volume PNNL-17471 830403000. United States Department of Energy, Pacific Northwest National Laboratory , August 1, 2012.

Other sources

Coordinates: 46 ° 24 ′ 0 ″  N , 120 ° 30 ′ 0 ″  W.