New Mexico Geological Society Annual Spring Meeting — Abstracts

The disciplines of pedology and geomorphology have been integrated with great success, helping to illuminate processes of landform development during the Quaternary. In this research we show that the recent history of the fluvial system in a small drainage basin can be understood by coupling the detailed descriptions of soils with geomorphic and other field criteria. While many soil-geomorphologic studies have been conducted on the Pajarito Plateau, located on the east flank of the Jemez Mountains of northern New Mexico, relatively few have been conducted on the Jemez Plateau, located on the west flank. The study area is part of the Rio Calaveras drainage, which is cut into the Bandelier Tuff and located approximately 3 km west-northwest of the Valles Caldera. Fluvial landforms that dominate the inner valley at the site are shown to have developed within the past 700 years. Two distinct, laterally continuous geomorphic surfaces are observed. The upper surface is a fluvial terrace, located between 2 and 3 meters above the current stream level, and the lower surface is the current floodplain, located about 0.5 meters above the active channel bed. Each of these surfaces exhibit different degrees and types of soil development which we conclude are both time and space dependent. The ages of the soils and associated surfaces were derived in part by establishing ages through preliminary dendrochronological studies of the trees on the surfaces. The initial stages of pedogenesis occur rapidly in many environments (Birkeland, 1984); and therefore rates of soil development on the surfaces are reflected in time dependent soil features. On such a short time-scale, spatial dependence is also very important to consider. For example, the presence of a single tree has greatly
influenced local soil development. Studying and interpreting the history and evolution of late Holocene fluvial systems such as this one requires an interdisciplinary approach involving geomorphology, sedimentology, pedology, and ecology. This research is the first stage of a larger project to be conducted as a part of Master's thesis at the University of New Mexico. This study should help better define the geomorphic framework in which the hydrologic system is operating, thereby providing valuable input to ongoing hydrogeoecologic studies of nutrient cycling related to a seasonally fluctuating water table.