Kansas Geological Survey, Open-File Rept. 96-1a
Proposed Management Areas--Page 3 of 16
Other Significant Aquifer/Aquitard Units Influencing the Dakota Aquifer
Over its extent in Kansas, the Dakota Formation is overlain
by younger Upper Cretaceous bedrock units and Cenozoic
unconsolidated deposits (Table 1,
Figure 1). The Upper
Cretaceous sequence consists of shale, chalk, and limestone
belonging to the Graneros Shale, the Greenhorn Limestone, the
Carlile Shale, the Niobrara Chalk, and the Pierre Shale. The
total thickness of this sequence generally increases to the
west and north in Kansas up to more than 2,400 ft in the northwest
corner of the state. These stratigraphic units form the Upper
Cretaceous aquitard (Figure 1).
In most of southwest and most
of south-central Kansas and much of southeastern Colorado, the
Upper Cretaceous aquitard has been eroded and the Dakota is
overlain by and hydraulically connected to the overlying High
Plains aquifer (Figure 1).
In the river valleys of the central
part of the state the Dakota aquifer is in hydraulic connection
with the overlying saturated alluvial deposits which form the
alluvial valley aquifers (Figure 1).
Westward dipping Jurassic and Permian rocks directly underlie
the Dakota aquifer in Kansas. In southwestern Kansas the
Jurassic Morrison Formation consists mostly of sandstone and
is a source of fresh water along with the Cheyenne Sandstone.
In central Kansas, the Cedar Hills Sandstone is a
saltwater-bearing aquifer that is hydraulically connected
to the lower Dakota aquifer (Table 1,
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Kansas Geological Survey, Dakota Aquifer Program
Original report available from the Kansas Geological Survey.
Electronic version placed online July 1996
Scientific comments to P. Allen Macfarlane
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