WASHINGTON DIVISION OF GEOLOGY AND EARTH RESOURCES OPEN FILE REPORT 2004-3

Division of Geology and Earth Resources Ron Teissere - State Geologist

117°30¢ 117°22¢30² 27¢30²B R.42E. R.43E. 25¢ 47°45¢ 47°45¢ Geologic Map of the Qmw Qmw Spokane Northwest 7.5-minute Quadrangle, Qfs

Qfs Spokane County, Washington Qfs

Ql „gr by Robert E. Derkey, Michael M. Hamilton, and Dale F. Stradling „wp Ql 2004

„l INTRODUCTION Glacial flood deposits, predominantly gravel „wp Qfg (Pleistocene)—Thick-bedded to massive mixture of boulders, Qaf Previous geologic map coverage of the Spokane Northwest 7.5-minute „gr cobbles, pebbles, granules, and sand; contains beds and lenses of quadrangle was reconnaissance and lacked sufficient detail to be of service sand and silt; gray, yellowish gray, or light brown; poorly to Qaf to developers and planners in the area. We undertook detailed mapping of moderately sorted; both matrix and clast supported; locally the quadrangle in 1999 and completed it in 2000. Our field mapping and air composed of boulders in a matrix of mostly pebbles and coarse photo interpretation was drawn on a U.S. Geological Survey topographic sand; derived from granitic and metamorphic rocks similar to Qml Qmw map of the quadrangle and then digitized and overlaid on digital those exposed both locally and to the northeast and east in Idaho; NORTHSIDE orthophotos from the Washington State Department of Natural Resources found mainly outside of the principal flood channels, which Qmw (1995 edition). Digital contours furnished by the Spokane County approximate the present courses of the Spokane and Little „l geographic information system (GIS) and the orthophotos were then used as Spokane Rivers. LANDFILL supplemental base maps to add to and refine geologic unit contacts on the final version of the map. Glacial flood-channel deposits, predominantly gravel Qfg Qfs Qfcg The first published geologic map of the area was by Pardee and Bryan (Pleistocene)—Thick-bedded to massive mixture of boulders, (1926). Griggs (1966) completed a 1:125,000-scale geologic map of the cobbles, pebbles, granules, and sand; may contain beds and Qmw western half of the Spokane 1- by 2-degree quadrangle. He later extended lenses of sand and silt; gray, yellowish gray, or light brown; Qfs „l his mapping eastward to complete a 1:250,000-scale map of the entire poorly to moderately sorted; both matrix and clast supported; „l Spokane 1- by 2-degree quadrangle (Griggs, 1973). Joseph (1990) compiled locally composed of boulders and cobbles in a matrix of mostly Qal Qal a 1:100,000-scale map of the Spokane quadrangle that incorporated more pebbles and coarse sand; derived from granitic and metamorphic detailed interpretations of Pleistocene glacial features based on Kiver and rocks similar to those exposed both locally and to the northeast

LATAH FAULT others (1979) and basalt stratigraphy based on Swanson and others (1979). and east in Idaho. This unit differs from flood gravel (unit Qfg) in In 1993 and 1994, Wendy Gerstel and others of the Washington State that it fills deep, ancestral channels of the Spokane and Little Department of Natural Resources mapped the Quaternary deposits related to Spokane Rivers, which now form the Spokane Valley–Rathdrum the Spokane aquifer recharge and aquifer sensitive areas at 1:24,000 scale; Prairie aquifer. The flood deposits filling the channels are known this unpublished mapping has been available to Spokane County officials to be several hundred feet thick. Boundaries between this unit Qaf since 1996 through the county’s GIS. and unit Qfg are based on location of these channels rather than „gr clast-size differences.

„l DESCRIPTION OF MAP UNITS Pre-Quaternary Igneous and Sedimentary Rocks Qfcg Qfcg Quaternary Sedimentary Deposits 42¢30² 42¢30² Priest Rapids Member of the Wanapum Basalt, Columbia Modified land (Holocene)—Land that has been modified by „wp Qml River Basalt Group (middle Miocene)—Dark gray to black, Qal excavation and (or) redistribution; consists of the Northside fine-grained, dense basalt consisting of plagioclase (20–30%), Qfcg Landfill. pyroxene (10–20%), and olivine (1–2%) in a mostly glass matrix Alluvium (Holocene)—Silt, sand, and gravel deposits in (40–60%); variable thickness; very thin where it laps upon pre- Qal present-day stream channels, on flood plains, and on lower Miocene highlands; lies directly on pre-Miocene rocks, Latah Qal Formation, or Grande Ronde Basalt; contact with the underlying T.26N. T.26N. terraces; consists of reworked glacial flood deposits (units Qfcg, Qfg, and Qfs) and reworked loess; may include small alluvial Grande Ronde Basalt occurs between 2,200 and 2,300 ft T.25N. A¢ elevation in the northwest part of the quadrangle. The contact „gr T.25N. fans and minor mass-wasting deposits that extend onto the flood plain from tributaries. between the Priest Rapids Member and underlying Grande „gr Ronde Basalt or Latah Formation extends below 1,900 ft Alluvial fan deposits (Holocene)—Gravel, sand, and silt elevation in the southern part of the quadrangle. This suggests Qaf Qal deposited in fans at the base of steep drainages; very poorly that a channel existed and was filled with the Priest Rapids sorted; most lack a large drainage source; minimal soil Member prior to the basalt spreading out over the terrain at 2,200 development. feet elevation and higher. Basalt is of the Rosalia chemical type (Table 1), which has higher titanium and lower magnesium and Loess (Holocene and Pleistocene)—Silt with lesser amounts of chromium than other flows of Wanapum Basalt (Steve Reidel, Ql clay; locally includes small amounts of fine sand and volcanic Pacific Northwest National Laboratory, oral commun., 1998). Qal Qfcg ash; light to medium brown; unstratified; clay mostly This unit is between 14.5 and 15.3 m.y. old and has reversed montmorillonite and illite in a ratio of 3:1, with minor kaolinite magnetic polarity (Reidel and others, 1989). Qfcg (Hosterman, 1969); sand and silt composed of angular quartz Grande Ronde Basalt, magnetostratigraphic units R and N , with lesser amounts of feldspar and mica. „gr 2 2 „gr Columbia River Basalt Group (middle Miocene)—Dark gray Qal Bog deposits (Holocene and Pleistocene)—Peat with lesser to dark greenish gray, fine-grained basalt consisting of pale green Qb Qfcg amounts of silt, ash, marl (bog lime), and gyttja (freshwater mud augite and pigeonite grains (10–40%) and plagioclase laths and with abundant organic matter); located predominantly in sparse phenocrysts (10–30%) in a matrix of black to dark brown Qal Channeled Scabland depressions on basalt bedrock (Milne and glass (30–70%) and opaque minerals; locally vesicular with Qmw others, 1975). plagioclase laths tangential to vesicle boundaries; some vesicles Qfcg contain botryoidal carbonate and red amorphous secondary „gr Qal Mass-wasting deposits (Holocene and late Pleistocene)— Qmw minerals; thickness is quite variable due to irregular underlying Landslide debris with lesser amounts of debris flow and rock-fall topography, variable thickness of water-saturated Latah deposits; consists mostly of a mixture of basalt blocks and Latah Formation (unit Ml) interbeds, and the invasive nature of at least Qal Formation sediments; basalt blocks range in size from several Qb some of the Grande Ronde Basalt flows in the area; identified in „gr feet to hundreds of feet in diameter. Most mass-wasting events Qfg the map area on the basis of chemical analyses (Table 1); Qb occurred during or shortly after Pleistocene catastrophic flood Qfcg between 15.6 and 16.5 m.y. old (Reidel and others, 1989). Qal events, but some mass wasting continued to the present; mass- Qb wasting events that occurred during glacial flooding incorporated Latah Formation (middle Miocene)—Lacustrine and fluvial „l „l flood materials consisting of scattered sand and pebble lenses deposits of finely laminated siltstone, claystone, and minor Qb Qal interspersed with the mass-wasting deposits. sandstone; light gray to yellowish gray and light tan; commonly weathers brownish yellow with stains, spots, and seams of The following units are deposits from outburst floods of glacial Lake limonite; poorly indurated; unconformably overlies pre-Miocene „l Missoula. They are a composite of numerous flood events and do not rocks or is interbedded with Grande Ronde Basalt (unit Mgr); „wp represent deposits from any single flood event. easily eroded and commonly blanketed by colluvium, talus, and residual soils; floral assemblages indicate a Miocene age Glacial lake and glacial flood deposits, undifferentiated Qmw „gr Qglf (Knowlton, 1926; Griggs, 1976); exposures are of limited extent Qfcg (Pleistocene)—Fine-grained, massive and thin-bedded lake „gr in the quadrangle, but logs from water wells drilled on Fivemile 40¢ 40¢ deposits of sand and silt interbedded with irregularly distributed Prairie indicate a thickness of more than 100 ft. A glacial-flood sand and gravel; tan to gray; locally exposed in the bed of Hangman Creek but mostly occurs on valley walls; Hornblende biotite granitic rock (Tertiary to Cretaceous) Qglf TKg Qal probably filled most of the valley before being dissected by later (cross sections only)—Based on exposures in the Spokane area, „l Qal „gr Qb „gr floods and post-flood stream action. Qb consists of medium-grained granitic rock; contains biotite „gr crystals up to 0.2 in., hornblende, and minor zircon; light gray Qfcg Glacial flood deposits, predominantly sand Qal Qfs with some light-pink feldspars; porphyritic in part, with feldspar (Pleistocene)—Medium-fine- to coarse-grained sand and Qal crystals up to 0.5 in. Qal granules with sparse pebbles, cobbles, and boulders; may contain Qfcg beds and lenses of gravel; composed mainly of granitic and Qb „l metamorphic detritus from sources to the east and of local basalt; GEOLOGIC SYMBOLS „gr gray, yellowish gray, or light brown; subangular to subrounded; Contact—Long dashed where approximately located; „gr poorly to moderately well sorted; medium bedded to massive; Qb short dashed where inferred or indefinite appears speckled in some exposures because of the mixture of Qfcg light and dark fragments; distribution uneven and thickness Fault—Short dashed where inferred or indefinite; dotted variable due to irregular underlying topography and varying where concealed degrees of erosion; appears to have been deposited when glacial Qb „wp Qal Qfg Lake Missoula outburst floods flowed into a high stand of glacial Water well—Numbers correspond to well numbers on „gr Lake Columbia. cross sections Qmw

Qb Qmw Basalt geochemistry sample location—Numbers correspond to sample numbers in Table 1 Qb „gr Qb „wp Qmw Qb Qfg Table 1. Geochemical analyses of Columbia River Basalt Group basalt performed by x-ray fluorescence at the Washington State University GeoAnalytical Lab. Instrumental precision is described in detail in Johnson and others (1999). Total Fe is expressed as FeO

„l Qb MAJOR ELEMENTS—UNNORMALIZED (in weight percent) TRACE ELEMENTS (in parts per million) Qfg „wp Qb Sample no. SiO2 Al2O3 TiO2 FeO MnO CaO MgO K2O Na2O P2O5 Total Ni Cr Sc V Ba Rb Sr Zr Y Nb Ga Cu Zn Pb La Ce Th „gr Qb Priest Rapids Member of the Wanapum Basalt (unit „wp) Priest Rapids Member of the Wanapum Basalt (unit „wp) „wp LATAH FAULT 101NW 50.08 12.69 3.622 15.28 0.250 8.51 4.64 1.25 2.82 0.787 99.93 15 31 43 424 561 28 283 215 50 18.0 23 22 153 8 22 62 3 Qal „wp Qfg 102NW 50.40 12.83 3.647 14.85 0.244 8.59 4.62 1.35 2.80 0.797 100.13 20 32 42 428 585 32 287 215 50 18.5 22 27 152 9 17 59 3 Qb „wp 103NW 50.18 12.80 3.660 14.95 0.241 8.53 4.54 1.32 2.84 0.802 99.86 17 30 41 427 577 30 286 218 52 19.0 23 26 150 6 36 74 2 Qb SNW1001 50.33 12.84 3.669 13.62 0.226 8.65 4.45 1.31 2.66 0.787 98.54 7 27 30 461 530 29 289 206 49 19.4 25 15 151 3 22 67 5

„l „wp Grande Ronde Basalt (unit „gr) Grande Ronde Basalt (unit „gr) „wp „l 113NW 56.74 13.79 2.147 10.43 0.208 6.90 3.24 1.97 3.15 0.387 98.96 6 16 33 295 800 50 332 189 38 14.3 23 13 122 6 13 64 9 Qb 114NW 54.57 13.08 2.428 12.95 0.203 6.87 3.18 1.66 3.24 0.416 98.60 4 14 39 347 684 42 313 184 39 13.5 22 13 130 7 29 63 7 Qfg „wp „l Qal Qfg Qb Qb Qfg Qglf Qb „wp ACKNOWLEDGMENTS Joseph, N. L., compiler, 1990, Geologic map of the Spokane 1:100,000 „wp Qb quadrangle, Washington–Idaho: Washington Division of Geology 47°37¢30² 47°37¢30² Eugene Kiver of Eastern Washington University, Geology Department, 27¢30² Qfs „gr R.42E. R.43E. 25¢ and Earth Resources Open File Report 90-17, 29 p., 1 plate. 117°30¢ B¢ 117°22¢30² accompanied us on numerous trips to examine Quaternary deposits in the area. Bea Lackaff of the Spokane County Water Quality Kiver, E. P.; Rigby, J. G.; Stradling, D. F., 1979, Surficial geologic map of the Spokane quad, Washington: Washington Division of Geology Spokane R. Management Program digitized the unpublished geologic mapping of Lambert conformal conic projection SCALE 1:24 000 Deep Cr. Little and Earth Resources Open-File Report 79-11, 1 sheet, scale 1 0.5 0 1 MILE Spokane Wendy Gerstel and others into Spokane County's GIS. Steve Reidel of North American Datum of 1927; to place on North American 395 R. Pacific Northwest National Laboratory (Richland, Wash.) provided 1:250,000. Datum of 1983, move the projection lines 15 meters north E E 10000 1000 2000 3000 4000 5000 6000 7000 FEET TS assistance during a two-day visit in the field to examine Columbia and 79 meters east as shown by crosshair corner ticks DEEP Knowlton, F. H., 1926, Flora of the Latah Formation of Spokane, AIRWAY 1 0.5 0 1 KILOMETER CREEK SPOKAN SPOKAN Base map from scanned and rectified U.S. Geological Survey HEIGH River Basalt Group stratigraphy and reviewed an earlier version of the Washington, and Coeur d’Alene, Idaho. In Shorter contributions to 2 NORTHWESTSpokane NORTHEAST 7.5-minute Spokane NW quadrangle, 1974, photorevised 1986 Cr. map. general geology 1925: U.S. Geological Survey Professional Paper Shaded relief generated from U.S. Geological Survey 10-meter contour interval 20 feet Deep E E 140-A, p. 17-81.

Digital Elevation Model FOUR MEDICAL LAKE LAKES SPOKAN SPOKAN REFERENCES CITED Hangma Milne, S. S.; Hayashi, S. K.; Gese, D. D., 1975, Stratigraphy of Digital cartography by Charles G. Caruthers and J. Eric Schuster 90 SOUTHWEST195 SOUTHEAST

Editing and production by Karen D. Meyers 395 scabland meadows in southeast Spokane County [abstract]: n Griggs, A. B., 1966, Reconnaissance geologic map of the west half of Cr. the Spokane quadrangle, Washington and Idaho: U.S. Geological Northwest Scientific Association, 48th Annual Meeting, Program A A¢ Survey Miscellaneous Geologic Investigations Map I-464, 1 sheet, and Abstracts, abstract no. 81. SW NE scale 1:125,000. Pardee, J. T.; Bryan, Kirk, 1926, Geology of the Latah Formation in Griggs, A. B., 1973, Geologic map of the Spokane quadrangle, relation to the lavas of the Columbia Plateau near Spokane, „wp Washington. In Shorter contributions to general geology 1925: U.S. NWW6 NWW5 Washington, Idaho, and Montana: U.S. Geological Survey NWW4 NWW3 Geological Survey Professional Paper 140, p. 1-16. 2000 „l Qmw 2000 Miscellaneous Geologic Investigations Series Map I-768, 1 sheet, „gr NWW2 scale 1:250,000. Reidel, S. P.; Tolan, T. L.; Hooper, P. R.; Beeson, M. H.; Fecht, K. R.; „l Spokane River Bentley, R. D.; Anderson, J. L., 1989, The Grande Ronde Basalt, „gr Qal Griggs, A. B., 1976, The Columbia River Basalt Group in the Spokane Columbia River Basalt Group; Stratigraphic descriptions and „l Qfcg Qfcg quadrangle, Washington, Idaho, and Montana; with a section on correlations in Washington, Oregon, and Idaho. In Reidel, S. P.; „gr Qfcg Petrography, by D. A. Swanson: U.S. Geological Survey Bulletin 1413, 39 p., 1 plate. Hooper, P. R., editors, Volcanism and tectonism in the Columbia 1500 „gr 1500 River flood-basalt province: Geological Society of America Special Elevation (ft) „l Hosterman, J. W., 1969, Clay deposits of Spokane County, Washington: Paper 239, p. 21-53. U.S. Geological Survey Bulletin 1270, 96 p., 1 plate. „l „l Swanson, D. A.; Anderson, J. L.; Bentley, R. D.; Byerly, G. R.; Camp, Johnson, D. M.; Hooper, P. R.; Conrey, R. M., 1999, XRF analysis of V. E.; Gardner, J. N.; Wright, T. L., 1979, Reconnaissance geologic rocks and minerals for major and trace elements on a single low map of the Columbia River Basalt Group in eastern Washington and vertical exaggeration 4x dilution Li-tetraborate fused bead: Advances in X-ray Analysis, northern Idaho: U.S. Geological Survey Open-File Report 79-1363, 1000 1000 v. 41, p. 843-867. 26 p., 12 plates.

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Qmw NWW1 „gr „wp „wp Qfg NWW8 2000 Qmw 2000 Disclaimer: This product is provided ‘as is’ „l without warranty of any kind, either expressed or NWW7 Spokane River Spokane River Spokane River „l „gr implied, including, but not limited to, the implied Qal „gr warranties of merchantability and fitness for a „l „l particular use. The Washington Department of „l Qfcg Natural Resources will not be liable to the user of „gr this product for any activity involving the product Elevation (ft) with respect to the following: (a) lost profits, lost Qfcg savings, or any other consequential damages; (b) 1500 „l 1500 the fitness of the product for a particular purpose; „l or (c) use of the product or results obtained from use of the product. This product is considered to TKg be exempt from the Geologist Licensing Act [RCW 18.220.190 (4)] because it is geological research conducted by the State of Washington, Department of Natural Resources, Division of vertical exaggeration 4x Geology and Earth Resources. 1000 1000