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n <br />U <br />• <br /> <br />Fine-grained_slope_outwash_SpedimentZ_deposits are de- <br />rived mostly from the Mancos Shale. These deposits occur <br />southeast of the river, and are distinguished from the pedi- <br />ment deposits northwest of the river by virtue of the parent <br />materials. The deposits are generally loosely consolidated <br />material of fluvial and colluvial origin; silt or clayey silt <br />with sand and gravel. Occasional areas contain cobbles or <br />infrequent boulders. <br />Co_arse-grained_sl_ope_outwash_(pediment)_deposits are simi- <br />lar in genesis to the above material, but are derived from dif- <br />ferent source rocks. These deposits are found northwest of the <br />river and contain a much greater percentage of the larger <br />sized material. This larger sized material consists of numer- <br />ous cobbles and boulders of basaltic rocks; they are partly <br />rounded, probably as a result of a short transport by water. <br />Basaltic rocks are probably derived from intrusions or flows <br />north of the study area. Locally, a considerable percentage <br />of well-rounded cobbles and boulders have been found within <br />this geomorphic unit. This material, formed by granitic and <br />metamorphic rocks is derived from old river terraces identi- <br />fied also north of the North Fork Gunnison river. It is very <br />probable that the slope outwash of this geomorphic unit is <br />more recent than the terraces. <br />C_olluvial-soils are fine-grained deposits containing fre- <br />quent angular rock fragments. These deposits are primarily <br />0 <br />the result of gravity action on relatively steep slopes. The <br />material generally consists of sandy or silty clays with fre- <br />quent cobbles and boulders relatively angular in shape. These <br />deposits also contain many boulders of basalt. <br />A-3 <br />~~wROCOnsu~n~,mc. <br />