Saturated thickness of the Madison aquifer, Black Hills, South Dakota.

This data set is a polygon coverage created in ARC/INFO that
represents the saturated thickness of the Madison aquifer, which
includes the entire thickness of the Madison Limestone and
Englewood Formation in the Black Hills area, South Dakota. The
unconfined zone of the Madison aquifer is the area where the
potentiometric surface of the aquifer is below the top of the
formation. The elevation of the top of the potentiometric
surface of the Madison aquifer was subtracted from the top of the
Madison Limestone, and the boundary of the unconfined zone
was created where the calculation results equalled zero.
The saturated thickness of the aquifer in the unconfined zone
was determined by subtracting the elevation of the top of the
Deadwood Formation from the potentiometric surface elevation of
the Madison aquifer. The potentiometric surface and the tops of
the formations where determined from water levels and geologic
logs from selected wells drilled as of 1998. The thickness coverage
contains polygons that have single integer values representing
a range of thickness.