ARCHITECTURE OF THE SIERRA-LADRONES FORMATION, CENTRAL NEW-MEXICO - DEPOSITIONAL CONTROLS ON THE PERMEABILITY CORRELATION STRUCTURE

Statistical models of hydrogeological heterogeneity are often used in aquifer and reservoir characterization. The number of data required to estimate objectively the spatial correlation structure of permeabilit y, however, is often prohibitive. The objective of this study was to d evelop a better understanding of how information about depositional pr ocesses can be used to characterize hydrogeological heterogeneity. An outcrop of the fluvial/interfluvial Sierra Ladrones Formation of New M exico was studied for this purpose. On the basis of previous studies o f paleogeography and our own field observations, deposits of the Sierr a Ladrones Formation are interpreted as marginal ancestral Rio Grande flood-plain and tributary deposits. Architectural elements were mapped over a 0.16-km2 peninsular out-crop of Pliocene-Pleistocene deposits of the central Albuquerque Basin. Geostatistical analysis of the archi tectural-element map data indicates non-orthogonal anisotropy in the h orizontal direction. The orientations of the strongest (N30-degrees-W) and weakest (N90-degrees-E) correlation correspond to the orientation of the tributary system and the ancestral Rio Grande flood plain, res pectively. In the vertical direction, the correlation structure exhibi ts exponential behavior corresponding to the average-element thickness es. The results demonstrate that information about depositional enviro nment can be used to help to quantify statistically subsurface heterog eneity.