New Mexico Geological Society Annual Spring Meeting — Abstracts

Soils-geomorphic studies and basin morphometric and morphologic analysis form the basis for evaluating the influence of differing bedrock lithology on the geomorphic evolution of Kim-me-ni-oli Wash drainage basin. Evolution of tributary basins within thie study area, preservation and distribution of surficial deposits, soil development, landscape stability, and erosion and transport of sediment have been bedrock influenced. Early basin history was marked by uniform degradation relative to dynamic erosion and deposition during the Holocene.

Ephemeral, discontinuous Kim-me-ni-oli Wash (1200 km²), a southern tributary to Chaco River, traverses gently, north-dipping Cretaceous strata. Mudstones and resistant channel-sandstones dominate lower and middle basin regions (lower 55 km); sandstones and shales underlie upper basin regions (upper 35 km). Middle and upper basin regions preserve landscapes possessing well-developed soils. Isolated remnants of older landscapes in lower basin regions are associated with resistant bedrock and record former base-levels. Small tributary basins in upper basin regions have consistent ranges in relief; relief ratio decreases proportional to increasing distance of tributary basin outlet to Kim-me-ni-oli Wash; basin shape and hypsometric integral increase proportional with distance (i.e., basins are more circular and less eroded as distance increases). Lower basin regions did not respond uniformly or systematically to base-level lowerings despite proximity to Chaco River; resistant sandstones inhibited uniform base-level migration and resulted in wide ranges in relief, variable hypsometry, and areas of temporary landscape stability. Local, stable landscapes are dissected when tributary basin rejuvenation occurs by breaching of resistant sandstones and/or modification of valley fill by complex geomorphic response, and results in local base-level change. Stripping of sandy surficial mantles increases exposure of less permeable bedrock units and results in variable sediment yield and basin hydrology.