Soil relative dating of moraine and outwash-terrace sequences in the northern part of the upper Arkansas Valley, central Colorado, USA

Profile development indices for soils developed in moraines and outwash nea r Twin Lakes and in outwash near Leadville support the correlation of morai nes with subdued morphology and two high outwash terraces with the Bull Lak e glaciation (ca. 130-160 ka) and the correlation of hummocky moraines and two low outwash terraces with the Pinedale glaciation (ca. 14-47 ka). Elsew here in the northern part of the upper Arkansas Valley, glacial sequences a re correlated by mapping outwash terraces near the mouths of major tributar ies of the Arkansas River. Near Twin Lakes, indices for soils on low, outer lateral moraines suggest that the older Pinedale glaciers extended beyond the margin of high, younger Pinedale lateral moraines with hummocky topogra phy. A few subdued moraines near Twin Lakes and Leadville probably record o ne or more glaciations significantly older than the Bull Lake. The downvall ey extent of Pinedale glaciers in the Mosquito Range on the east side of th e Arkansas Valley is uncertain: most likely, Pinedale glaciers were almost as extensive as Bull Lake glaciers but built no prominent terminal moraines at their maximum positions.