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Kootenai County, Idaho

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Kootenai County, Idaho Bayview 116o3000 Cs 47o5800 Lake Priest Rv Qmf Pend Spirit Lake Complex Oreille Tgdd Athol Ymil Yc Twin Lakes 95 Kgdh 116o1945 Kog Kgdh Ymil YcY Yc Tgss Yra ath Yc P Ymiu Yra d o Rathdrum o Ymil l Ts YXm F Ymil la N u Kgdh Yc Yc o Tcr F s o r Ymiu is Hayden k Yra Yc 53 M Qmf Yra Co Lake eu r Post Falls Yra d Yra Yc A Yp l Kog e Coueur Tcr n dAlene Lewis & Clark e Yp R Ts Ts fault zone v Ts Tcr 84 Yp YXm Tcr Yp Ts Kog Yra Rose Cataldo Yp Lk e k Qa a Ts L Killarney Lk. e n le 95 A d Yp r Yra Qa u Tcr e Yra o C Tcr Qa Yra Care Lk Tcr Yp Yp Tcr YXm 3 47o2500 Ts Tcr 116o1945 Ts Yra Yra 47o2200 Yra 117o0231 0 5 10 miles 0 8 16 kilometers 1:500,000 Digital Atlas of Idaho, Sept. 2002 http://imnh.isu.edu/digitalatlas Compiled by Reed Lewis, Idaho Geological Survey http://www.idahogeology.org Kootenai County The bulk of Kootenai County south and east of Coeur dAlene is underlain by Mesoproterozoic Belt Supergroup rocks continuing west from their extensively mineralized area along the Lewis and Clark fault zone, in the Silver Valley in Shoshone County. The western part of the county, west of Coeur dAlene Lake and the Rathdrum Prairie belongs to the lower plate of the Priest River core complex. The normal fault bounding the uplifted metamorphic rocks of the core complex dips eastward and follows the north-trending basin of Lake Coeur dAlene. The south fork of the Coeur dAlene River contains mining wastes from the Silver Valley. The area near Rose and Killarney Lakes as well as at Cataldo, contains a layer of zinc and lead-rich gravel or tailings, in the shallow subsurface. When the lake level changes these mine wastes are disturbed and metals may be released into solution. This is an ongoing scientific, political, and economic challenge. The Lake Missoula Floods charged southwestward down the Rathdrum Prairie toward Post Falls, and into the Spokane River in eastern Washington. Miocene Columbia River basalts cover the rolling Palouse country of the southwestern part of the County, north of the Coeur dAlene Tribal Casino. Cretaceous intrusive rocks are found in the core of the Priest River uplift south of Coeur dAlene, and northeast of Hayden Lake. Eocene granitic rocks intrude the core complex west of Spirit Lake. Written by P.K. Link, 9/02 Symbols Yp Geologic unit contacts with unit designation. Overturned anticline: trace of axial plane. Normal fault: certain; dashed where Overturnedsyncline: trace of axial approximately located; dotted where plane. concealed. Location of ISU Rockwalk rock Thrust fault: certain; dashed where from each county. approximately located; dotted where concealed. Cities Detachment fault: certain; dashed Feature location where approximately located; dotted where concealed. Roads Anticline: trace of axial plane: large 15 Interstate Route arrow indicates direction of plunge. U.S. Route Syncline: trace of axial plane: large 95 arrow indicates direction of plunge. 1 State route Description of Units for Kootenai County, Idaho Qa Quaternary alluvial deposits Qmf Missoula Flood deposits; boulder bars and gravel along route of Missoula flood on Rathdrum Prairie south and west of Lake Pend Oreille. Ts Tertiary sedimentary rocks, undifferentiated. Includes Oligocene and Eocene sedimentary rocks in east-central Idaho (Paleogene basins of Janecke). In northern and western Idaho this unit contains Miocene lake and stream deposits formed adjacent to and above the Columbia River and Weiser basalts, which formed dams in stream canyons. Tcr Miocene basalt (Columbia River Basalt Group); flood basalt, extensively exposed in western Idaho; fed by fissures, many of which are near the Idaho-Oregon border. Flowed eastward up valleys cut into the Idaho mountains. Tgdd Eocene granodiorite and dacite porphyry intrusive, also includes diorite and, in northern Idaho, minor granitic rock; intermediate phase of Challis magmatic event (50 to 46 Ma). Summit Creek stock. Tgs Eocene granite, pink granite, syenite, rhyolite dikes, and rhyolitic shallow intrusive; last phase of the Challis magmatic event (46 to 44 Ma). Forms craggy scenic mountain landscape in central and northern Idaho. Kgdh Cretaceous granitic rocks of the hornblene-biotite suite; granite, granodiorite and megacrystic granodiorite. Potassium (K) rich. Age about 80 to 90 Ma. Kog Cretaceous orthogneiss, and foliated granodiorite and granite (includes mylonitic plutonic rocks in western Idaho suture zone); deformed early phases of the Idaho batholith. Cs Cambrian sedimentary rocks. Yag Mesoproterozoic augen gneiss and porphyritic granite; near Shoup on the Main Salmon River age is 1370 Ma. Ymiu Upper Missoula Group. Includes Swauger Quartzite, Lawson Creek Formation in Lemhi Range, and Striped Peak and Libby formations In northern Idaho. Ymil Lower Missoula Group. Includes Gunsight Formation in Lemhi Range and upper Wallace Formation (equivalent to Snowslip and Shepard formations) in northern Idaho. Yc Piegan Group or Middle Belt carbonate, Apple Creek Formation [includes lower and middle Wallace Formation in northern Idaho and Apple Creek Formation and argillaceous quartzite (including rocks at Cobalt) near Salmon]. Yra Ravalli Group, sandstone (quartzite) and siltite, includes Big Creek Formation and lower part of Lemhi Group in Lemhi Range and Salmon River Mountains, and Burke, Revett and St. Regis formations in northern Idaho. Yp Prichard Formation (Lower Belt), dark fine-grained siltstone and sandstone, calcareous intervals in Boehl's Butte area. YXm High-grade metamorphic rocks (schist, gneiss, quartzite, calc-silicate rocks); includes Elk City metamorphic sequence and related rocks, Syringa metamorphic sequence, and Priest River metamorphic complex..
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