THE FLORIDA PHOSPHATE DEPOSITS. 37 
Incoherent sand.. .... 2 fO 4 feet 
Indurated gray sand grading below into phosphate matrixi2 to 16 feet 
Workable phosphate stratum.... 10 to 12 feet 
Yellow clay marl, “bed rock” (exposed).. 5 feet 
The upper 5 or 6 feet of the sand of this section contain some 
clay and are stained red by iron oxide. At the base the sands pass 
gradually into the pebble rock conglomerate. Beneath the pebble 
rock conglomerate the matrix is more clayey while near the base the 
clays of the matrix are olive green in color. The conglomerate as 
seen in this pit differs from that seen in the pit of the Coronet Phos¬ 
phate Company in the absence of corals along the contact line. 
The relation between the phosphate bearing formation and 
the underlying marl or limestone is well seen in the pit of the 
Pierce Phosphate Company, six miles south of Mulberry. The. 
marl exposed in this pit, as previously stated, has a very roughly 
eroded surface. (PI. 4, Fig. 1.) The phosphate matrix fills these 
irregularities. At this pit there is observed in places below the 
Workable phosphate matrix one to three feet of material consisting 
of quartz sand intimately mixed with small black phosphatic peb¬ 
bles. An old stream channel crosses this pit. In the bed of the 
stream is fine loose, more or less stratified dark colored sand. This 
stream where examined has cut down to the coarse part of the 
phosphate matrix and at one point almost cut out this coarse part 
of the matrix, that is it has cut through the sand and the 
upper part of the phosphate formation. This stream occupies 
approximately the bed of an existing stream and probably indicates 
that conditions were such formerly as to permit the stream to cut 
its bed deeper than now, the channel subsequently having been ag¬ 
graded. Near by in the same pit is a sudden dip in the sand over¬ 
burden. (PI. 3, Fig. 3.) The point of break gives very much the 
character of a sink hole. 
CONDITION OF DEPOSITION. 
In attempting to determine the condition under which the land 
pebble phosphate formation accumulated, the characteristics of the 
formation itself should be borne clearly in mind. The formation 
is more or less definitely stratified. The stratification, however, 
is irregular, and cross bedding and local sand deposits occur. 
The phosphate bearing part of the formation is highly fossilifer- 
ous containing both land and marine vertebrates. Most of these 
fossil bones are more or less eroded and water worn, indicating 
that they have been rolled or washed before reaching their final 
resting place. Occasionally, however, a complete skeleton occurs. 
Water worn bones of both the land and marine vertebrates could 
