82 FLORIDA GEOLOGICAL SURVEY-SEVENTH ANNUAL REPORT. 
and flows west to Tampa Bay. It therefore cuts across the land peb¬ 
ble phosphates and in the lower part of its course cuts into the .Alum 
Bluff marl, from both of which formations the river pebble is de¬ 
rived. 
MANATEE RIVER. 
A limited amount of pebble phosphate is found along Manatee 
River and its tributaries derived largely from the Alum Bluff marl 
into which the river has cut its channel. 
NORTH CREEK. 
North Creek in Manatee County affords an interesting illustra¬ 
tion of the accumulation of pebble phosphate in successive forma¬ 
tions. This stream cuts into the Alum Bluff marl which at this lo¬ 
cality contains a considerable amount of phosphate pebbles. Rest¬ 
ing directly upon the marl is found a Pleistocene shell marl, which 
is likewise phosphatic, the pebble having been derived from the 
Oligocene marl beneath. Finally in the recent bars of the stream is 
found a mixture of shell, pebble phosphate and sand. 
CALOOSAHATCHEE RIVER. 
Dark colored phosphate pebbles similar to that on Peace Creek 
are found in the bed of Orange and Caloosahatchee Rivers in 
Lee County. That found along Orange River is derived from a 
yellow phosphatic marl which rises two or three feet above water 
level. The marl exposed here contains an abundance of large 
oysters, pectens and other invertebrates. The pebble phosphate of 
the Caloosahatchee river is probably derived from the same phos¬ 
phatic marl. If so, however, it lies beneath the typical Caloosa¬ 
hatchee marl and is nowhere exposed above water level. The Ca¬ 
loosahatchee marl, itself, contains occasional phosphate pebble and 
phosphatized casts of shells, but probably not in sufficient abundance 
to account for the accumulation of the phosphate in the bed of the 
river, particularly in the lower course of the stream. The phosphate 
pebble found in this river and its tributaries is doubtless derived 
either directly or indirectly from the Alum Bluff formation which 
although not exposed, probably lies at no great depth below the sur¬ 
face. 
