Like other sequences, the Zuñi was probably caused by a mantle plume - more specifically, the Mid-Cretaceous Superplume event.
A mass of unusually hot rock rose from the lower mantle to the base of the lithosphere, fueling a dramatic increase in seafloor spreading rates; this caused the hotter mid-ocean ridges to increase in volume, thus displacing the oceans onto the continents.
[2] Sea level rose in earnest beginning in the early Cretaceous, until by Cenomanian time it was roughly 250 metres (800+ feet) higher than today.
[3] This was the time of the great Western Interior Seaway and the widespread continental deposition of carbonates and shale elsewhere.
[6] The waters of the Zuñi sequence began to subside late in the Cretaceous period, and by the early Cenozoic a new craton-wide unconformity in North America indicates a complete regression before the Tejas sequence of the late Paleogene.