SURFICIAL GEOLOGIC MAP OF THE JEMEZ SPRINGS QUADRANGLE, NEW MEXICO; A CORRIDOR OF RAPID DEVELOPMENT AND KEY TO LATE CENOZOIC GEOLOGY AND GEOMORPHOLOGY ON THE SOUTHERN FLANK OF THE JEMEZ MOUNTAINS

The Jemez Springs quadrangle (JSQ) is located approximately 90 km northwest of Albuquerque in north central New Mexico on the western flank of the Jemez Mountains. In recognition of the importance of detailed surface information to the modern geologic map, field work for the surficial mapping of this quadrangle was completed in conjunction with the USGS EDMAP program at a 1:24,000 scale. The most prevalent surficial units in the study area are deep-seated landslides of Carboniferous Madera limestone, ubiquitous thin colluvial mantles, largely of Permian Abo and Yeso Formations on the steep canyon walls, and mesa top soils developed on Quaternary Bandelier Tuff. Numerous normal faults trend both north-south and northeast-southwest through the quadrangle.

Understanding the types, distributions, and erosion potential of JSQ surficial deposits is critical because the canyon is currently experiencing rapid economic and population growth as well as heavy recreational pressures. This mapping demonstrates that recent development has focused on unstable colluvial deposits of the valley walls that are prone to modern landsliding and on the relatively flat tops of old, deep-seated landslides that could become unsafe in the event of earthquake activity.

Remnant terrace treads preserved ~20 m above Jemez River grade are located in the northern portion of the JSQ, although no widespread terrace deposits characteristic of the quad immediately downstream are present. Limited roadcut exposures along the river also show fluvial gravels buried under colluvial and landslide deposits. These data extend the previously-developed Jemez River terrace stratigraphy upstream and yield insights into the morphotectonic development of the Jemez Mountains. The implication of these observations is not that fluvial terraces were never formed, but that they are not preserved as distinctive landforms due to mass wasting, information that will be used to constrain a terrace genesis and preservation model.