Oolite). The three facies interfinger locally and are approximately 130,000 years old 
BP. The Florida Keys are an archipelago of elongate coral limestone islands, near 
parallel to the present offshore reef, and extend from near Miami southwest to Bahia 
Honda Key, and continue under water as far west as the Dry Tortugas. The southern 
Keys from Big Pine Key to Key West consist of oolite facies with a northwestern trend, 
which is approximately at right angles to the trend of the reef and which reflects the 
old Pleistocene tidal influence of their development. To the north on the mainland, the 
oolitic facies occupies mot of the Atlantic Coastal Ridge from Boca Raton to a point 
southwest of Homestead and extends as a thin sheet several miles into the Everglades. 
The reminder of the exposed Miami Limestone is termed the bryozoan facies and covers 
an area of approximately 3,000 sq. mi from the southern coast of Florida into the 
Everglades. Diamond-drill cores taken of the bedrock in Florida Bay reveal that the 
bryozoan facies underlies most of the Bay, but in a more complicated manner than 
previously suspected. Patch reef(s) occur locally in the Bay; one has been identified 
just east of East Key about 45+ ft thick. In other parts of the Bay, freshwater 
limestone has been observed. The bryozoan facies is composed of peletal packstones and 
grainstones and is so named because locally up to 70% of the rock may be composed of 
colonies of the bryozoan Schizoporella floridana. After bryozoans, pellets are the most 
abundant constituent; other important constituents are miliolids, peneroplids and ooids, 
and locally the unit contains burrows and calcareous worm tubes. The facies of the 
Miami Limestone was deposited on a broad, shallow-water marine platform where 
water depths probably did not exceed 30 ft. Long, linear, low topographic highs occur 
on the Miami Limestone in Everglades National Park. Known locally as "rock reefs," 
their length ranges from 8 to 15 mi, width from 30 to 60 ft, and height up tp 3 ft. 
Morphologically they are similar to the carbonate mudbanks accumulating today in 
Florida Bay. 
1989 0 
Merriam, D. F., and T. M. Quinn (1989) Recent sediments of Bald Eagle Key and implications 
for Florida Bay island stratigraphy. Symp. on Florida Bay: A Subtropical Lagoon. Miami, FL. 
June, 1987. Bull. Mar. Sci. . 44(1):520. 
[ABSTRACT ONLY, DATE OF SAMPLING UNKNOWN OR NOT APPLICABLE.] Bald Eagle Key 
is low-lying, saucer-shaped, mangrove-fringed island in Florida Bay. Located in 
Everglades National Park between easternmost Bob Allen and Captain Key and south or 
Russell Key, it is one of approximately 170 such islands in the Bay. Most of the islands 
are connected by a series of narrow anastomosing mudbanks. In general the islands are 
larger in the northeastern part of the Bay adjacent to the mainland and the mudbanks 
are thicker and wider in the western part fronting on the Gulf of Mexico. The islands 
are composed of carbonate mud that has accumulated over the Miami Limestone 
(Pleistocene) "bedrock" during sealevel rise throughout the past 5,000 yrs. The 
"normal" stratigraphic succession (A) of sediments forming the islands consists of: (a) 
freshwater marl, (b) mangrove peat, (c) shelly marine carbonate mud, (d) sort, marine 
carbonate mud usually with live mangrove roots, and (e) a cream-colored flaky 
supratidal carbonate mud (locally laminated). On other islands, another sequence (B) of 
events consists of only: (a), (b) and (e). Events (a) through (c) have been interpreted 
as transgressive, and events (d) to (e) regressive. Interpretation of sequence (A) is 
that of islands formed by mangrove colonization of marine mudbanks; whereas for (B) 
islands nucleated from a supratidal precursor. Both mechanisms are equally viable for 
island initiation. If marine mudbanks form subsequent to island nucleation from a 
supratidal precursor, then the absence of evidence of a supratidal nucleus beneath an 
island can result from: (1) island migration and subsequent erosion, or (2) an 
insufficient sampling density. Twenty-nine soft sediment cores were taken on the 0.2 
by 0.4 m wide island. Sediment thickness ranged from about 7 to 8 ft with a 1- to 18-in 
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