Chapter 6 addresses the state’s major sedimentary rock aquifers or aquifer systems. Sedimentary rock aquifers are composed of consolidated clastic and carbonate deposits. Ground water in sedimentary rock aquifers can be either confined or unconfined. The major sedimentary rock aquifers in Colorado consist predominantly of sandstones and limestones of varying age. Many of these aquifers are located in structural basins that contain multiple geologic units and aquifers. Large quantities of ground water occur in deep basins such as the Denver Basin and in the flat-lying High Plains Aquifer of eastern Colorado. The state’s major sedimentary rock aquifers and aquifer systems are presented in Figure 4.2.