The purpose of phase 1 and phase 2 of the Department of Energy funded project Analysis of oil- bearing Cretaceous Sandstone Hydrocarbon Reservoirs, exclusive of the Dakota Sandstone, on the Jicarilla Apache Indian Reservation, New Mexico was to define the facies of the oil producing units within the Mancos Shale and interpret the depositional environments of these facies within a sequence stratigraphic context. As currently defined, there are two principal intervals of oil production within the Mancos Shale. The bulk of the oil production comes from sandy facies in the lower part of the Mancos in what is termed by drillers as the ?Gallup sandstone? or El Vado Sandstone; lesser production is from fractured shale. The focus of this report will center on 1) redefinition of the areal and vertical extent of the ?Gallup sandstone? or El Vado Sandstone Member of the Mancos Shale (Fassett and Jentgen, 1978), 2) determination of the facies distribution within the ?Gallup sandstone? and other oil-producing sandstones within the lower Mancos, placing these facies within the overall depositional history of the San Juan Basin, 3) application of the principals of sequence stratigraphy to the depositional units that comprise the Mancos Shale, and 4) evaluation of the structural features on the Reservation as they may control sites of oil accumulation. Discussion of the above is found in the text below and in a series of five cross sections (plates 1-5), one structure map (plate 6), and one appendix. The appendix includes a set of logged cores through various intervals in the Mancos and photographs of the core.