Ocala limestone in Marion County. Numerous sink holes that formerly connected underground channels with the surface are now filled with sand and clay. These filled sinks are reported by drillers to be common in parts of Seminole County, and in selecting locations for wells depressions resembling old sinks are avoided, because in some of them sand has been encountered to a depth of more than 200 feet, whereas normally limestone that yields water may be encountered at a depth of about 50 feet. Such a condition is reported to exist in the topographic depression just north of Oviedo*
In Seminole County the Hawthorn formation consists of interbedded marl, clay, and sand. The surficial Pleistocene and Recent material consists chiefly of sand, marl, clay, or muck.
Ground Water
Developments
Small domestic supplies of water are obtained in Seminole County from shallow wells that end in the surficial sands. Most of these are driven wells that are equipped with hand pumps. A few supplies are also obtained from wells that yield water from the Hawthorn formation. The chief source of ground water, however, consists of drilled wells that extend into the Ocala limestone and yield water that is under artesian pressure. It is estimated that there are about 1,500 drilled wells in the county, most of which are in the celery districts, near Sanford and Oviedo. Some of the fields have an average of one well for each acre of
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