36 FLORIDA GEOLOGICAL SURVEY--THIRD ANNUAL REPORT.
phate pebble, bone fragments, water worn flints and coral..3 4 feet
Buff yellow and olive green clay matrix in which phosphate
pebble is embedded..................................5 feet
The superficial pale yellow sand is of fine texture and is nonfossiliferous. The indurated gray sand is also non-iossilife( us in the upper part. Towards the base, however, this sand grades into the conglomerate previously mentioned, the lower one. to ole and one-half feet being a very rich phosphate conglomerate.
The break between the phosphate pebble conglomerate and te underlying phosphate matrix is very abrupt representing a local unconformity. (P1. 4, Fig. 2.) Aside from the phosphate there is found in this conglomerate lying along the line of contact a considerable amount of coral occurring as water worn fragments, some of which weigh as much as 8 or io pounds. The larger corals u sually lie immediately upon the contact line. Water worn flint pebbles of one or two pounds in weight, also occur together with fragments of bone.
The phosphate stratum lying beneath this unconformity is chiefly of bluish color which upon exposure oxidizes to a light buff yellow. Occasional bones and flint pebbles are found also in this part of the formation. The water worn corals, however. were not observed below the unconformity. That part of the phosphate matrix below the unconformity contains also many rounded pieces of soft phosphate while that above the unconformity contains hard pebble rock only.
POLK COUNTY.
A pit operated by the Standard Phosphate Company near Medulla is notable for the extreme irregularity in the stratification of the phosphate bearing member. The strata here are observed to dip at an angle of as much as 45 degrees from the horizontal. The bed rock which consists of the usual yellow clay marl is likewise irregular and is observed to rise as much as fourteen feet in a horizontal distance of 50 feet.
In the pit of the Medulla Phosphate Company at Christina, the following section was observed:
Incoherent pale yellow sand .............................:2 to 5 feet
Gray sand, iron stained near surface........................8 feet
Phosphate hearing matrix .............................1I5 to 20 feet
Yellow clayey marl, "bed rock" (exposed) ..................4 feet
In Pit No. 3 of the Prairie Pebble Phosphate Company, near Mulberry the following section was observed: