The Andes of southern Peru . Fia. 182—Dissected alluvial fans on theborder of tlie Urubamba Valley near HaciendaChinche. A characteristic feature of thevalleys of the Peruvian Andes below the zoneof glaciation but within the limits of its ag-graditional effects. Through alluviation thevalleys and basins of the Andean Cordillera,and vast areas of the great Amazon plains castof it, felt tlie effects of the glacial conditionsof a past age. they form a distinct thoughsmall piedmont fringe along the eastern base of the Andes, andthey are universal throughout the Andean valleys. That a depositof suc
The Andes of southern Peru . Fia. 182—Dissected alluvial fans on theborder of tlie Urubamba Valley near HaciendaChinche. A characteristic feature of thevalleys of the Peruvian Andes below the zoneof glaciation but within the limits of its ag-graditional effects. Through alluviation thevalleys and basins of the Andean Cordillera,and vast areas of the great Amazon plains castof it, felt tlie effects of the glacial conditionsof a past age. they form a distinct thoughsmall piedmont fringe along the eastern base of the Andes, andthey are universal throughout the Andean valleys. That a depositof such volume—many times greater than all the material accumu-lated in the form of high-level alluvial fans or terminal moraines—should originate in a tropical land in a region that suffered butlimited Alpine glaciation vastly increases its importance. 272 THE ANDES OF SOUTHERN PERU. •??.•.?VAUIV FILL The fill is composed of both, fine and coarse material laid dowaby water in steep valley floors to a depth of many feet. It breaksthe steep slope of each valley, forming terraces with pronouncedfrontal scarps facing the river. On the raw bluffs at the scarpsmade by the encroaching stream good exposures are Chinche in the Urubamba Valley above Santa Ana, the materialis both sand and clay with an important amount of gravel laiddown Avith steep valleyward inclination and under torrential con-ditions; so that \vithin agiven bed there may be anapparent absence of lamina-tion. Almost identical con-ditions are exhibited fre-, quently along the railway toCuzco in the Vilcanota Val-ley. The material is mixedsand and gravel, here andthere running to a bowlderyor stony mass where acces-sions have been receivedfrom some source is modified along its mar-gin not only in topographicform but also in compositionby small tributary alluvialfans, thou
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Keywords: ., bookcentury1900, bookdecade1910, bookidandeso, booksubjectgeology
