Mud Mound and Bank Depositional Environments

Mud banks form mounded to long, linear, low-energy deposits of bioturbated mud and shelly mud. Florida Bay has some of the world's best-developed and -studied mud banks. Mud accumulates in the mounds when currents are baffled by organisms such as sea grass or algae.

Florida Bay behind the Florida Keys, showing network of mud banks. Image by Scientific Visualization Studio, NASA Goddard Space Flight Center; data courtesy Landsat Project.

Mud Bank Model

Generally windward and leeward sides each produces a gradation of energy across the bank. In Florida Bay, sea grass stabilizes the banks. Island development is common along the tops of the banks, and tidal channels cut the banks. Enos (1983) presented a diagrammatic cross section of a Florida Bay mud bank. He showed that sea grass plays an important role in stabilizing the bank. In the ancient record, other organisms, such as algae, assumed this stabilization role.

From Enos (1983).

Oblique aerial photograph of mud banks in Florida Bay. Spy Key is in the foreground.

Island and tidal-channel development along Twin Keys mud bank in Florida Bay.

Rock Types

In the ancient record, these banks are represented by wackestone to packstone, with some lenses of grainstone. Where they are not well outlined, as in the photo below, they are difficult to distinguish from other muddy, platform-interior sediments because they have similar fabrics and textures.

Mud mound of Pennsylvanian age in Central Texas. Photography courtesy of Ursula Hammes.

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