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Qdf Debris-fan deposits (Holocene to lace Pluistucen~•): ,rnsurteJ, <br />tfZ unconsolidated debris of soil, ruck, and displaced vegetation <br />deposited where stream gradi. nt rluc:rcases. This i;r.rdirrrt <br />decrease most commonly near [Le cunLluencr• of a tribut.rry stream <br />with a larger trunk stream. Usu.rlly cumpusvd of muJ, shwt-, and <br />debris-fluty material, fire deposits result from the rapid iou vemen[ <br />and deposition of solid material during unusually hc.rvy rain or <br />snovmelt runoff. Qdf deposits probably formed during fife Holocene; <br />Qdf2 deposits most li~ely wore deposited during previous glacial <br />stages. <br />Qse Soil-tree /solifuction deposits (Ilulocerre): mixtures of sand, silt, <br />and clay with some larger ruck fragments formed by fire slow, dovn- <br />slope movement of near-surface materials. These deposits, charac- <br />terized by a series of small svales and ridges perpendicular to <br />direction of movement, generally are active anJ indicate areas <br />with unstable slope conditions. <br />Qda Debris-avalanche deposits (Holocene): unsorted mixtures of soil and <br />rock material formed by their generally sudden and rapid downslope <br />movement and deposition. Usually formed during periods of rainfall, <br />the deposits generally produce a relatively small, elongate rise <br />that may extend out to gently sloping areas below clue steep slopes <br />from which the materials uribtnate. <br />Qsfc Slope-failure-complex (unit) Juposits (Ilulocene to late Pleistocene: <br />'`sfeZ unsorted mixtures of soil and ruck material formed by various <br />~fc3 mass-wasting processes incluJin); landslides, earthflows, mudflows, <br />soil creep, and debris avalanches. Nut all of tlieso processes <br />• occur within a specific deposit :end [he age of movewen[ may very <br />with a particular area. Tliu {;eneral age of the unit is noted by <br />subscripts (L is the youngest). <br />Qts Talus/Scree deposits (Holocene to late Pleistocene): angular, unsorted, <br />pebble to boulder-size rock fragments that mantle muuntatn slopes or <br />accumulate at the base of a hereon-ruck mass. Ttre deposits usually <br />form steep, concave slopes and include talus cones and lobate ur <br />tongue-shaped rock glaciers. M:rss-wasting processes are currently <br />active in the formation of [Irusc deposits. <br />Qcw Colluvial-vedbe deposits (Hu_lorenu to _lace Pleistocene): unconsolidated, <br />heterogeneous soil material .end ruck fragments found near fire base <br />of a slope. Formed by gravity-dominated processes, the deposits may <br />be subject to continued mass-wasting. <br />Bedrock Units <br />Tb Basaltic intrusive rocks (Miocene): dark gray to black phorphyritic <br />intrusive rocks that contain fine-grained ptreucrysts of olivine and <br />pyroxene. <br />Tip Porphritic intrusive rocks (Miurenc anJ Oligocene): light-gray <br />porphyritic intrusive rock tl~,u vary in composition from quartz <br />. F-34 <br />Rev. 1: 0-18-81 <br />