FIRST QUANTITATIVE TEST OF ALLUVIAL STRATIGRAPHIC MODELS - SOUTHERN RIO-GRANDE RIFT, NEW-MEXICO

Since 1978 the results of computational architectural models have been widely used to aid interpretation of ancient alluvial successions: he re we present the first quantitative test of such models. We parameter ize variables from field and magnetostratigraphic data collected from the well-exposed Pliocene-Pleistocene Camp Rice and Palomas Formations of the Rio Grande rift in southcentral New Mexico. Computational runs establish that the LAB (Leeder, Alien, and Bridge) model correctly pr edicts the gross architectural patterns of ancestral axial Rio Grande half grabens and full grabens. Convergence of tectonic subsidence rate and mean sedimentation rate over the studied interval suggests that t he dynamic basis of the models is correct; i.e., it is the tectonic '' draw-down'' of axially supplied sediment that controls the net preserv ation potential of alluvial successions.