In phosphate pits of the Bone Valley district of Florida three different kinds of materials generally are exposed--Hawthorne bedrock or bedclay of Miocene age, overlying concentrations of phosphorite of Miocene and Pliocene ages, and a surface blanket of loose to slightly indurated quartz sand. The current concept that the surface sand blanket is an insoluble residue developed in situ through weathering, and as a consequence of this origin reflects the environments in which the underlying phosphorites accumulated, is concluded to be incorrect. This result is based on studies and comparisons of grain size analyses of quartz sand, on heavy mineral data and on fossil evidences. (cf. Fig. 4). The smaller ridge southeast of Bartow is the Bartow ridge. Those parts of the ridges higher than 180 feet are shown by a stippled pattern. The sites of all samples and sections referred to in the report are given. Circles and letters designate locations where channel samples were collected. These channel samples and the mine sites are labeled as follows: A--Boyette mine, B--Payne Creek mine, C--Palmetto mine, D--South Ridgewood mine, E--Clarke-James mine, F--Noralyn mine, G--Achan mine, H--Sydney mine, I--Orange Park mine, J--Lake Hancock mine, and K--Bartow mine. Sites at which spot samples were collected are shown by triangles and are as follows: 1--Palmetto mine, 2--Boyette mine, 3--Tenoroc mine, 4 Orange Park mine, and 5--Sydney mine. Stars and Roman numerals are used to designate the localities at which detailed studies and detailed sections were made. The localities are labeled as follows: I--Achan mine, II--Peace River mine, III---Pool Branch vertebrate site, IV--Grace drill hole, and V--Noralyn mine, Tiger Bay pit. 24•0 PIRKLE, YOHO, AND WEBB
Fzc. 2. Northern part of Bone Valley district. The Lakeland ridge as outlined by Altschuler and Young by means of the 160-and 180-foot contours is surrounded by lowlands
