114 
FLORIDA GEOLOGICAL SURVEY-I4TH ANNUAL REPORT 
Depth of sample. 
Possibly somewhat more granular, but otherwise not differing from the 
white limestone above .'.. 160-200 
A gray or light blue-gray, compact limestone not unlike that found at the 
depth of 130 feet, although possibly harder....... 260 
White granular limestone ......... 300 
Gray limestone, very compact. The sample contains, however, one piece 
which is very porous. .... 350 
Granular, white limestone ........... 375 
Porous, white limestone, appearing nearly cream-yellow in the powdered 
form ........ 430 
Material similar in character to the last, but of a darker color, nearly 
cream-yellow. 440 
Darker in color and may be described as a brown limestone, which is ap¬ 
parently rather porous .:. 445 
Mixture of brown and light-colored limestones, with occasional grains of 
silica, the brown predominating....... 460 
Dark brown, porous limestone......... 480 
Dark brown limestone ....... 500 
This well starts in the Ocala formation (Eocene), and is reported 
by Cushman to enter the Lower Cretaceous at 110 feet. 
MONROE COUNTY 
Monroe County extends to extreme south Florida and includes the 
Florida keys south of Key Largo. The surface formations in this county 
are Pleistocene or Recent in age, and include coral and oolitic and fresh¬ 
water limestones and sands. Underneath the Pleistocene are Tertiary 
sediments, and beneath the Tertiary is the Cretaceous. 
The log of a well at Marathon, in this county, has already been given 
(page 95). At this place the Lower Cretaceous fossils are recorded by 
Cushman at 1,248 feet. The log of a well at Key West, to a depth of 
2,000 feet, is given in the Fifth Annual Report of the Florida Geological 
Survey, page 288. This well is reported to have reached a total depth of 
2,398^2 feet.* 
NASSAU COUNTY 
Nassau County is on the Atlantic coast, in extreme northeast Florida. 
On the St. Mary’s River, which forms the west and north boundaries of 
this county, deposits of probably Pliocene and Pleistocene age are at the 
surface. Elsewhere in the county such limited exposures as are seen 
consist chiefly of sands and sandy clays of undetermined age. The Alum 
*U. S. Geol. Surv., Water Supply Paper 319, p. 372, 1913. 
