FISC - St. Petersburg
Tavernier Key: Tavernier Key is a nearshore mangrove island surrounded by a shallow bank (Fig. 48A, 48B). Like Rodriguez Key bank off Key Largo (Fig. 42B), Tavernier Key bank began to develop a few thousand years ago when sluggish water circulation in very shallow depths allowed mud to settle and collect in a concave bedrock indentation (Enos, 1983). Mud buildup continued with rising sea level, forming a mud bank that later developed a branching-coral (Porites) and coralline-algae (Goniolithon) rim. The solidified rim mostly lines the seaward side of the bank and protects the muddy mangrove island from incoming waves.
At Rodriguez Key, the oldest conventional 14C date (Turmel and Swanson, 1976) on mangrove peat now under water but recovered in cores was calibrated to correlate with ages obtained using high-precision age-dating methods. Calibration yielded an age range of about 6,530 to 6,180 cal. yr B.P. (Table 3). The old mangroves grew along the mudbank shoreline and thus post-date the bank, indicating that Rodriguez Key bank is older than 6,530 cal. yr B.P. The bank around Tavernier Key is likely the same age.
Tavernier Key bank differs from Rodriguez Key bank by having a carbonate sand beach in its central axis. Sailors once obtained fresh water from the water lens in the sand [Romans, 1775 (1962)].
Seaward of Plantation and Tavernier Keys, the Pleistocene reef rimming the shelf margin remains a fairly continuous structure in the Tile 2 sector, extending southwestward from The Elbow (Fig. 33A, 33B). Numerous sand chutes mark unevenness of the reef crest. The first major breaks or reentrants visible in aerial photos of the reef occur on either side of Crocker Reef (Fig. 48B).