A SOIL STRATIGRAPHIC ANALYSIS: LINKING TRIBUTARY BASINS AND ALLUVIAL FANS IN THE SE SAN JUAN MOUNTAINS, CO, USA
C14 dates combined with soil forming properties indicate three distinct periods- PH1 (11.5-7.0 ka years B.P.); H2 (6.5 - 3.5 ka years B.P.); H3 3.5 ka years B.P. – present) of sediment mobilization throughout SMG and RG that coincide with alluvial fan aggradation and correspond with climatic cooling events and periods of high frequency climatic change. PH1 time was marked by abundant sediment erosion and deposition in these basins. PH1 soils - 7.5YR or redder hues, strong ped structure and overall clay or silty clay textures- are generally buried at depths >50 cm. H2 aged soils - 7.5YR hues, moderate ped structure, and silty loam to sandy clay textures- are the dominate surface unit in the headwaters of SMG and RG and are found commonly as buried soils in the valley bottoms of both basins. H3 aged soils -10YR hues, weak ped structure and silty or sandy loam textures- dominate the surface soils of colluvial slopes, alluvial fans, and debris flows throughout SMG and RG. Our work demonstrates that sediment has been mobilized in spatially distinct areas in these tributary basins throughout the Holocene and that sediment mobilization is driven, at least in part, by climate fluctuations since the LGM.