Geologic features of areas of abnormal radioactivity south of Ocala, Marion County, Florida

Areas of abnormal radioactivity south of Ocala, Marion County, Fla., discovered in 1953 by aerial survey, were investigated by surface examination and by 10 power auger drill holes. Inter-bedded clay, clayey sand, and uraniferous phosphorite occur in the areas of anomalous radioactivityo Miocene fossils occur at three localities in these beds which are evidently outliers- of Miocene sediments on the Ocala limestone of Eocene age. The preserved outliers are southwest of the main belt of Miocene sediments.

The principal uraniferous rocks are clayey, sandy, pellet phosphori1te that occurs in beds a few feet thick, and very porous, phosphatic sand rock which makes abundant float at many places. Apatite forms the phosphate pellets in the unweathered phosphorite. The very porous, phosphatic sand rock is the highly leached residuum of the pellet phosphorite and is composed mainly of quartz, kaolinite, wavellite, and crandallite (pseudowavellite). It closely resembles the aluminum phosphate rock of the 'leached zone' of the Bone Valley formation in the land-pebble phosphate district.