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A A' varies in height from 50 feet above the river near the confluence with Cherry Creek to 20 feet near Brighton. 4980 \ TKd \ SI'R COI........- //.....' Qblo ..,,( TXd Y - LOlMEn IEDftOC. ~IUM -' The South Platte River cuts into the Broadway Terrace on the left side of the valley floor near 88th Avenue east of Thornton in Adams County. The Broadway Terrace is sand and gravel fill of the Wisconsin Stage. The upper phase is clean course sand composed of granite, quartz and gneiss fragments, approximately 15 feet in thickness. Underneath, is coarse gravel and cobbles, some exceeding 6 inches in diameter composed of the same materials as the sand above. 8 4990 -'fIR /"// /, //, TKd ~ ~ . ~~ ;X/:/);>/ >/~ ' \2,,.~,,/ //./ // /<//~ /'/;, ~_~~~!~ItOf '/> / Qb.." / /' /// / // / /./ //'/,/ /7 co.....-cI.Uf ..troct..ttI , / .- / / / / / /./ .,r d.,..U. "--_ TKd c ........- L.ouvIon' - /:,/:- /><<: //</,,<:.~: /' s ///-~:>:'<<-~~~::>~;<::~~~>'>1 ~ TKd '/.'. ...//.....//////~//~//0. .'~ ~'~j::;~~/~~-LL:~/ - / - I ~ "'~b/1\"'" Tkd Oft At other places along the valley floor through Denver and along the left valley wall downstream from Clear Creek, there are terraces of Piney Creek alluvium. Its thickness is generally more than 8 feet. The South Platte River does not cut into the Piney Creek alluvium. D 5010 ::;..-'" L.ouvie,., A ------.-- /~;r~-----~" . ~'///; COl. ,...-- .~~ , //-//./ ~ TKd ~.:.::""":.k.,;;;;_.:==~ 5020 /"" ........., ""- ~ ~ Q'~ ;: ./~ _ TKd 40 //....-...-....--- 50 / W 5000 2000 10 .... The Denver Formation constitutes the left or west edge of the South Platte River from its confluence with Cherry Creek to its confluence with Clear Creek, To the east side of the valley, the landscape surface is Eolian sand and silt blown out from the river valley and areas to the west. To the west of the valley the surficial materials are mostly Eolian silt and residual soils. The major supply of sand to the South Platte River has been from its right or east bank tributaries. The left or west bank tributaries have carried more clays, silts and gravels. For the most part, the South Platte River is incised in or is flowing on the Wisconsin Stage gravel fill. The geological cross-sections of the valley in Figure VII-2 show the different formations in the valley. Adams County The South Platte River in Adams County lies just north of the deepest part of the Denver-Julesberg Basin. Bedrock in the Adams County portion of the study reach is the Denver Formation. TKd CROSS SECTIONS SOUTH PLATTE RIVER ADAMS COUNTY HENDERSON 10 BRIGHTON 8' h.~nd SPR: Qblo: Qes2 : Qp: Tkl: VII-3 South Platte River Broadway-Louviers Alluvium Eolian sand & silt Piney Creek Alluvium Denver Format i on See Figure VII-1 for locations of cross- sections. FIGURE VII-2