Two distinct geometries of "lime" mud and sand bars (parallel with and transverse to topographic restriction) have formed in association with a linear bedrock ridge of Key Largo Limestone along the eastern (seaward) border of Biscayne Bay, Florida.

On the south the bedrock ridge forms an emergent chain of keys, and currents are restricted to natural channel passes. Narrow, elongate sand "stringer shoals" extend from 2 of these passes into the bay, transverse to the trend of the bedrock ridge.

The bedrock ridge on the north is submerged 1-3 m below MLW, and a well-developed mud-bar belt (8 m long and 1-3 mi wide) parallels the bedrock ridge and lies mostly along its bayward side. Tidal channels 300 ft wide have formed perpendicular to the belt. Storm spillover lobes have extended the belt seaward of the now-covered ridge.

The crest of the bedrock ridge is 0-1 m below MLW in a central zone. There, relic transverse "stringer shoals" are incorporated into a presently developing mud-bar belt which parallels the bedrock ridge and lies entirely along its bayward side. Tidal channels cutting the mud-bar belt are irregular in form. The relic "stringer shoals" became inactive during the latter stages of the Holocene as sea level encroached over the bedrock ridge permitting unrestricted circulation of tidal currents.

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