6.1 DENVER BASIN
The water-yielding strata of the Denver Basin aquifer system consists predominantly of sandstones and siltstones of Tertiary- and Cretaceous-age. The northern part of the Denver Basin aquifer system underlies the alluvial aquifer of the South Platte River, and locally is hydraulically connected to that unconsolidated aquifer. In descending order, the geologic formations that contain the Denver Basin aquifers are Tertiary- and Cretaceous-age siltstone, sandstone, conglomerate, and shale of the Dawson, Denver, Arapahoe, and Laramie Formations, and Fox Hills sandstone (Figure 6.1-3). The four statutory aquifers contained in these formations are named the Dawson, Denver, Arapahoe, and Laramie-Fox Hills. Table 6.1-1 provides a summary of the geologic and hydrologic characteristics of the Denver Basin aquifer system. As much as 7,000 feet of nearly impermeable Pierre Shale underlies the Fox Hills sandstone.
Figure 6.1-3 General geologic cross sections through the Denver Basin.
Modified from Robson, 1987.