Erosion and deposition on the Pajarito Plateau, New Mexico, and implications for geomorphic responses to late Quaternary climatic changes

Abstract

The gently-sloping mesa tops and adjoining canyons of the Pajarito Plateau contain a diverse record of late Quaternary landscape changes that was probably strongly affected by fluctuations in climate. The streams show considerable variability in their behavior during the Holocene, with some experiencing progressive incision into tuff that was interrupted by periods of lateral cutting and floodplain development, while others experienced progressive aggradation interrupted by episodes of channel cutting into alluvial fills. Available data indicate that many streams were incised below their present level in the late Pleistocene and have subsequently aggraded in the Holocene, and this aggradation was probably due to a major increase in sediment supply within the drainage basins accompanying the Pleistocene-Holocene transition. Although the processes producing such accelerated erosion are not fully understood, they may have been aided by an enhancement of intense summer rainfall in the early Holocene. Widespread erosion has continued into modem times, progressively stripping soils from mesa tops, including welldeveloped soils that are older than 50-60 ka, and exposing tuff bedrock in many areas. Additional effects of climatic change near the Pleistocene-Holocene transition may have included an increased 2/8/96 1996 NMGS Guidebook