IDAHO GEOLOGICAL SURVEY DIGITAL WEB MAP 179 MOSCOW-BOISE-POCATELLO IDAHOGEOLOGY.ORG FEENEY AND PHILLIPS GEOLOGIC MAP OF THE MIDVALE QUADRANGLE, WASHINGTON COUNTY, IDAHO City of Midvale Well SW 1/4 SW 1/4 sec. 8, T. 13 N., R. 3 W. Well logs 364619 and 398035 Dennis M. Feeney and William M. Phillips Feet Below Ground Surface 0 Gravel and Overburden 2016 CORRELATION OF MAP UNITS Sand and Gravel Artificial Alluvial Deposits Sedimentary Deposits Deposits Qafo QTs? Qt1 100 QTs? Qaw m Qt Qlp Qaw Qas QTs? Ts Qaw Qaf Qaw 1 Holocene Qaf Ts Qt1 Qaf 0.01 ka Ts QUATERNARY Qt Qt ? 1 2 423902 Qt Twb 2 Ts 2 ª Pleistocene 200 Qas QTs? Qas Qafo QTs QTs? Qaw Blue Clay Qt 1 Qas 2.6 Ma Qaf ? 300 Qt1 Ts Qafo Qt1 Pliocene m Qaw ? Qaw Qas 5.3 Ma Volcanic Rocks 400 Qaw Qaw Rhyolite and Basaltic Basalt Qaf andesite andesite TERTIARY Qaw 436355 Weiser volcanics ª 367711 Qas BX6031* ª Twb 500 Basalt 288654 2 427441 Qaf Ts Ts ª Twb Miocene A 376249 ª 1 359569 ª 14.9 ± 0.57 Ma* Shale and Rock Stringers ª 289163 Twba 600 ª 15.1 ± 0.16 Ma* Basalt m Ts Green Shale Qaw 289500 367717 Tmv Columbia River Qaw m ª ª Basalt Group Basalt (very hard) Broken Basalt with Water Tgr1 700 Qaw ? Basalt (very hard) Qaf Gray Shale *Richard Gaschnig, personal comm., 2015. BX6032 Basalt Shale Qt Basalt 1 800 Qafo ª 364619 424042 Shale Qas ª 365834 Basalt Ts Blue Shale Qas ª Twb Qaf 2 Brown Shale and Sand 424657 Qt1 Qaw ª SYMBOLS 900 ALLUVIAL DEPOSITS Qaf Contact: dashed where approximately located. Basalt Qlp Lake and playa deposits (Holocene and Pleistocene)—Fine sand, silt, and clay sorted into thin laminar beds deposited during periodic floods around small Qt Normal fault: ball and bar on downthrown side; dashed where approxi- TD 990 feet 1 man-made reservoirs. Figure 1. Photograph looking southwest of QTs ª Qaf mately located; dotted where concealed. sediments as they appear at lat. 44.4414˚ N. long. 1000 337894 Qt1 Qas Alluvium of side streams (Holocene)—Clayey sand, silt, and fragments of shale 116.7402˚ W. The perspective is from the banks of the Weiser River looking up at the sequence. Estimated strike and dip direction of volcanic flows. in small channels draining landscapes underlain by Tertiary sedimentary Figure 2. Log of water well drilled for the City of Midvale based Qaf Qt2 deposits (Ts). In streams draining basaltic landscapes such as Sage Creek upon records filed with the Idaho Department of Water Resources. Qt1 367711 Water well showing Well ID number. Selected water wells shown with and Dry Creek south of Midvale, deposits are predominantly well-rounded The well was drilled to a depth of 963 feet below ground surface 288686 Idaho Department of Water Resources WellID number. Water well logs on June 15, 1962. At that time, the well had artesian closed-in Qt basaltic cobbles. In Dutch Flat, unit includes broad unchanneled areas 1 QTs pressure of 175 psi, flow rate of 2000 gpm, and water temperature ª m can be found at underlain by thin re-worked eolian sediments. Thicknesses range from <1 http://www.idwr.idaho.gov/apps/appswell/RelatedDocs.asp? to 2 m (<3 to 6.5 ft). Many tributary streams are ephemeral. Subject to VOLCANIC ROCKS of about 80°F. The well was deepened to 990 feet on November 25, 1983. At that time, well had artesian closed-in pressure of 158 WellID=xxxxxx where “xxxxxx” is the six-digit WellID. seasonal flooding during spring snowmelt and summer thunderstorms. psi, flow rate of 800 gpm, and temperature of 81°F. Original well Weiser volcanics logs are available at http://www.idwr.idaho.gov/apps/appsWell/ Qaw 14DF303 Geochemical sample location. Qaw Alluvium of Weiser River (Holocene)—Well-rounded cobbles and coarse- to m Twb RelatedDocs.asp?WellID=364619 and http://www.idwr.idaho. 2 Weiser basalt 2 (Miocene)—Medium- to dark-gray with shades of purple, fine- Qaf medium-grained subrounded sand; cobbles dominated by dark-gray to gov/apps/appsWell/Related Docs.asp?WellID=398035. Ts m R Fluxgate magnetometer reading location (R - reverse, N - normal). black mafic volcanic rocks, with rare light-gray to yellowish tuffs and to medium-grained basalt. Phenocrysts and microphenocrysts compose 15 QTs granitic rocks. Sand consists of quartz, feldspar, and black and orange-gray percent; phenocrysts are plagioclase as long as 3 mm, iddingsite up to 2 Ts Patterned ground: Circular to elongate silty mounds separated by gravelly lithic fragments. Micas are absent. Forms cobble point bars with braided mm, olivine, and augite; the remaining 85 percent is groundmass. Normal Qt1 Qt1 zones form a pattern of contrasting soil characteristics and vegetation channels 1 to 1.5 m (3 to 5 ft) deep. Islands and tops of some bars have thin magnetic polarity as determined in the field (fluxgate magnetometer) and Qt Qaf REFERENCES 2 that are readily mappable from aerial images. The mounds average 9 to deposits of arkosic sand. Thickness estimated at 2 to 3 m (6.5 to 10 ft). by laboratory paleomagnetic analysis (Feeney and others, 2014; Garwood Qt 2 29 m (30 to 95 ft) in diameter and 0.3 to 2 m (1 to 6 ft) in height. They Inundated during spring snowmelt or during winter rain-on-snow events in and others, 2014). Formerly mapped as the Star Butte member of Weiser Qaw 14DF303 are associated with a grain size contrast that varies from silt and clay in headwaters. Basalt by Fitzgerald (1982). Consists of up to four flows ranging from about Feeney, D.M., D.L. Garwood, and W.M. Phillips, 2014, Geologic map of the Qt1 m QTs N the mounds to gravel in the intermounds. The patterned ground occurs 3 to 9 m (5 to 30 ft) in thickness (Fitzgerald, 1982). Outcrops are long ridges Mann Creek SE quadrangle, Washington County, Idaho: Idaho Geological Qt Lower terrace alluvium of Weiser River (Holocene)—Predominantly well- on surfaces of gravel terraces, alluvial fans, and basalt flows with 1 with rare colonnades, or blocky well-vesiculated flow tops in gullies or Survey Digital Web Map 169, scale 1:24,000. BX6041 rounded basaltic cobbles and brown silty sand and clayey sand; water wells varying degrees of weathering. Malde (1964) noted that patterned flats. Generally a capping unit; however, preexisting structures and eleva- Feeney, D.M., R.S. Lewis, W.M. Phillips, D.L. Garwood, and S.W. Cooley, Twb2 indicate thickness of about 1.8 to 6 m (6 to 20 ft). Subject to flooding during tion around Star Butte (a possible vent) apparently caused Twb to flow Twb ? Qt ground of soil mounds and stone pavements is common in southern 2 2016, Geologic map of the Hog Creek Butte quadrangle, Washington and 1 1 spring snowmelt or during winter rain-on-snow events in headwaters. around older Twb . Source areas are uncertain. Chemical analyses from 14DF302 Idaho on gravel fans, basaltic lava flows, and rocky colluvium. His 1 Adams counties, Idaho: Idaho Geological Survey Digital Web Map 174, Qas Separated from Qt2 by a 3 to 6 m (10 to 20 ft) scarp. this quadrangle and adjacent quadrangles shows Twb with a SiO content Qas description is aptly applied to the best-developed patterned ground 2 2 scale 1:24,000. QTs ranging from 46.29 to 48.94 percent, TiO content ranging from 1.60 to observed in this quadrangle: “Soil mounds in flat areas are closely Qt Higher terrace alluvium of Weiser River (late Pleistocene)—Water wells 2 Fitzgerald, J.F., 1981, Geology and basalt stratigraphy of the Weiser embay- 2 2.64 percent, and P O content ranging from 0.56 to 0.95 percent (Table 1; Qt packed, monotonously uniform circular heaps 50-60 feet across and 3 (427657, 424042, 436355) indicate 4.9 to 6 m (16 to 20 ft) of cobble gravel 2 5 ment, west-central Idaho: University of Idaho Ph.D. dissertation, 121 p. Qaw 1 Feeney and others, 2014; Feeney and others, 2016; Garwood and others, Qaw feet high, but on slopes they are elliptical and lie in rows along paths of topped with about 1.5 m (5 ft) of brown silty sand or silty clay. Gravel pit in Fitzgerald, J.F., 1982, Geology and basalt stratigraphy of the Weiser embay- Qaf BX6040 2014); differences in composition may reflect separate flows. Interbeds of soil that trend downhill. Each mound is composed of a lens-shaped cap sec. 7, T. 14 N., R. 3 W. is developed in this unit. ment, west-central Idaho, in Bill Bonnichsen and R.M. Breckenridge, eds., of silt about 18 inches thick, abruptly underlain by 1-2 feet of brown tuffaceous material, ash, breccia, or Ts are present locally between Cenozoic Geology of Idaho: Idaho Bureau of Mines and Geology Bulletin Qaw BX6043 14DF330 clay” (Malde, 1964: p. 191). It is likely that the patterned ground Qaf Alluvial fan deposits (Holocene and late Pleistocene)—In Middle Valley, individual flows and above or below the unit; no attempt was made to 26, p. 103-128. m formed through periglacial processes during times of colder climate in consists of crudely bedded, poorly sorted, gray to brown sand, silt, and clay show the interbeds unless mappable at 1:24,000 scale. Fitzgerald, J.F., 1984, Geology and basalt stratigraphy of the Weiser embay- Ts m the Pleistocene. These processes are investigated and modeled by derived from Tertiary sedimentary deposits (Ts). These fans have coalesced Twb ment, west-central Idaho: Rockwell International Corp., Richland, WA, Twb N 1 Weiser basalt 1 (Miocene)—Purplish-gray to dark-gray, fine- to coarse-grained 1 N Kessler and Werner (2003), who attribute the resulting landform to into semi-continuous fan aprons that interfinger with gravels and sands of Rockwell Hanford Operations, RHO-BW-SA-217P, 121 p.