Preliminary examination of the distribution, texture, and chemical composition of clay minerals in the Morrison Formation suggests that the sandstone of the Westwater Canyon served as a conduit for potassium- and aluminum-rich, possibly warm, fluids that moved updip from the center of the basin toward the basin margin, giving rise to mineral zonation within the sandstone over a lateral distance of approximately 35 km.

The observed patterns include: (1) Pure smectite occurs as grain coatings in the Westwater Canyon Member in the shallowest core; this smectite is texturally similar to mixed-layer illite-smectite found in the deeper cores. (2) Expandability of the illite-smectite decreases toward the center of the basin and is more expandable near the upper and lower sandstone-mudstone contacts than at the center of the sandstone. This illite-smectite is generally highly ordered and frequently exhibits well-defined superlattice peaks. (3) Iron-rich chlorite occurs texturally on top of the smectite and illite-smectite and therefore must be later. (4) Smectite in the overlying Brushy Basin Member and in the underlying Recapture Member remains 100% expandable through the area analyzed. (5) Kaolinite, the latest clay mineral to form, is most abundant in the middle cores, decreasing in the shallow cores and in the deeper cores.

The fluid movement event probably occurred subsequent to the basin formation during Laramide time. Diagenetic reactions are more extensive in the deeper sections, near the basin center, and have obliterated some chemical and mineralogical relationships which are still observable in the shallower cores.