REPORT OF INVESTIGATIONS No. 38 7
aquifer, and the Floridan aquifer. Cross sections A-A', B-B', and C-C' in figure 3 show the character and distribution of the material composing the water-table and the first and second artesian aquifers. A generalized section and a generalized electrical resistivity log of the expected material at the site of the proposed waterway is shown in figure 4. The section shows the hydrologic units into which the material has been divided. The straight-line part of the resistivity log indicates the part of the material that is generally cased off in wells.
The water-table aquifer extends from the surface of the ground to about 18 feet below sea level. It consists of interbedded sandy limestones, sands, and shells. The aquifer may contain beds that are under artesian conditions, but the data are not adequate to delineate these beds. None of the wells for which records are available tap this aquifer except test wells 1, 2, and 3 (fig. 3). The aquifer, however, will probably produce adequate water for domestic purposes.
Below the water-table aquifer are beds about 20 feet in thickness that have a relatively low vertical permeability. These beds confine water in the first artesian aquifer. The material in the upper part of these beds is similar to the material in the water-table aquifer but contains more clay and has a lower permeability. The lower part is a sandy, argillaceous dolomite, which is soft to hard and similar to the material in the first artesian aquifer. The horizontal permeability of these beds in places may be high enough so that they will produce small amounts of water.
The first artesian aquifer lies below the upper confining beds, is about 15 feet thick, and is composed of sandy dolomite or dolomitic limestone that contains hard and soft layers. The aquifer seems to be moderately permeable, but the permeability seems to be lower in the west line of wells than in the easternmost wells of the south line.
Eleven wells in the Venice well field tap only this aquifer, and 27 tap the first artesian aquifer and the second artesian aquifer.
A second confining bed, about 15 feet thick, separates the first artesian aquifer from the second artesian aquifer. The bed occurs over a wide area and consists of very fine sandy clay or silt of low permeability. This bed has been found in wells at Sarasota, some 20 miles north of Venice, and in wells just south of Venice.
The second artesian aquifer consists of hard to soft, dense to porous dolomite and extends from about 70 to 130 feet below sea level. Water in the aquifer is confined under artesian pressure.