Geologic map of the Frisco quadrangle, Summit County, Colorado [report]

2002 unpublished
af Artificial fill (recent)-Compacted and uncompacted rock fragments and finer material underlying roadbed and embankments along and adjacent to Interstate 70. Also includes material comprising Dillon Dam dt Dredge tailings (recent)-Unconsolidated, clast-supported deposits containing mostly wellrounded to subrounded, cobble-to boulder-size clasts derived from dredging of alluvium for gold along the Blue and Swan Rivers; similar dredge tailings along Gold Run Gulch are too small to show on map.
more » ... redge tailings were mapped from 1974 air photos; most tailings have now been redistributed and leveled for commercial development Qal Alluvium (Holocene)-Unconsolidated clast-supported deposits containing silt-to boulder-size, moderately sorted to well-sorted clasts in modern floodplains; includes overbank deposits. Clasts are as long as 1 m in Blue River channel; clasts are larger in some side-stream channels. Larger clasts are moderately rounded to well rounded. Includes some wetland deposits in and adjacent to beaver ponds along Ryan Gulch. Maximum thickness unknown, but greater than 10 m in Blue River channel Qw Wetland deposits (Holocene)-Dark-brown to black, organic-rich sediment underlying wetland areas, commonly containing standing water and dense willow stands. Maximum thickness estimated to be about 15 m Qav Avalanche deposits (Holocene)-Unsorted, unstratified hummocky deposits at the distal ends of avalanche-prone hillside in Sec. 16, T. 5 S., R. 77 W. Contains clasts as long as about 1 m and abundant logs and wood fragments. Maximum thickness about 10 m Qry Active rock-glacier deposits (Holocene)-Hummocky, lobate deposits of mostly angular boulders having frontal slope at angle of repose. Deposits are ice cored and moving; boulders are not covered with lichen. One small deposit in Secs. 16 and 21, T. 6 S., R. 78 W grades downslope into inactive rock-glacier deposit (unit Qr). Maximum thickness about 30 m Qr Inactive rock-glacier deposits (Holocene and upper Pleistocene)-Hummocky, lobate deposits of angular boulders and smaller clasts having a frontal slope near the angle of repose; boulders on frontal slope partly covered by lichens. In places, grades into and includes some talus (unit Qt). In cirques on east side of Tenmile Range. Maximum thickness about 25 m Qtr Travertine (Holocene)-Brown to reddish-brown vuggy travertine in two roughly flat-coneshaped deposits, each about 15 m in diameter, in S ½ Sec. 21, T. 5 S., R. 77 W., near Snake River inlet. Springs feeding travertine not currently active, but unweathered nature of deposits suggests (late?) Holocene age. Deposits less than about 5 m thick Qf Fan deposits (Holocene and upper Pleistocene)-Moderately well sorted sand-to boulder-size gravel in fan-shaped deposits from side streams of Blue River Valley, Tenmile Creek, and below gully in northeastern corner of quadrangle. Deposits both matrix and clast supported, suggesting range in water content during transport. Clasts mostly subangular to subrounded and as long as about 2 m; most are considerably smaller. Include minor stream alluvium and debris-flow deposits. As much as about 15 m thick Qt Talus (Holocene and upper Pleistocene)-Angular and subangular cobbles and boulders on steep mountain sides and below cliffs. Boulders generally are as large as 2 m, although in places are as large as 10 m. Sandy matrix rarely exposed as surface. Talus mapped extensively on both sides of crest of Tenmile Range and commonly grades into felsenmeer (fields of frost-shattered bedrock boulders, which are mapped as underlying bedrock unit) near crest of range. As much as 20 m thick Qc Colluvium (Holocene and upper Pleistocene)
doi:10.3133/mf2340 fatcat:5clq2kinjvchnd3zmtbeda7ygm