36 FLORIDA GEOLOGICAL SURVEY—THIRD ANNUAL REPORT. 
phate pebble, bone fragments, water worn flints and coral. .3^ 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 non- 
fossiliferous. The indurated gray sand is also non-fossilifen us 
in the upper part. Towards the base, however, this sand grades 
into the conglomerate previously mentioned, the lower one to one 
and one-half feet being a very rich phosphate conglomerate. 
The break between the phosphate pebble conglomerate and the 
underlying phosphate matrix is very abrupt representing a local 
unconformity. (PI. 4, Fig. 2.) Aside from the phosphate there 
is found in this conglomerate lying along the line of contact a con¬ 
siderable amount of coral occurring as water worn fragments, some 
of which weigh as much as 8 or 10 pounds. The larger corals us¬ 
ually 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 unconformi¬ 
ty 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 stratifica¬ 
tion of the phosphate bearing member. The strata here are ob¬ 
served to dip at an angle of as much as 45 degrees from the hori¬ 
zontal. 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 bearing matrix...15 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: 
