Patch-Reef Depositional Environments

Patch reefs occur in the platform interior where energy levels are high and circulation is good. They commonly initiate on paleotopographic highs. Patch reefs can be as much as tens to hundreds of meters across and tens of meters high. Corals and other framework organisms cover up to 50 percent of the surface, along with carbonate sand between the corals. Patch reefs can have windward and leeward sides, with the windward side having more coral growth. Some patch reefs, such as the rhomboid patch reefs in southern Belize lagoon, have deep minilagoons in their centers. Islands can form on the patch reefs with associated sand or gravel beaches.

Patch Reefs behind the Barrier Reef in Southern Belize

Circular patch reefs in the platform interior behind the Belize barrier reef. Water depth is up to 30 meters between the patch reefs.

Dense, massive coral growth on the patch reef.

Dense coral growth of platy and stick-shaped corals on the patch reef.

Platy coral (Acropora palmata) growing on the patch reef.

Rhomboid Patch Reefs in Southern Belize with Deep Central Lagoons

Rhomboid patch reefs in the platform interior behind the Belize barrier reef.

Thickets of Acropora cervicornis coral cover the surface of the rhomboid patch reefs.

Rock Types

Patch reefs are common in the ancient record and occur as boundstones with associated packstones and grainstones. The frame-building organisms changed through time but all played the same role in the construction of a topographic, high-energy-positive area, as compared with the adjacent low-energy muddy or sandy areas.

Truncated rudist patch reef with accretionary talus bedding from the Lower Cretaceous in Texas.

Caprinid rudist bafflestone from the Lower Cretaceous in Texas.

Branching hydrozoan bafflestone from a patch reef in the Lower Cretaceous of South Texas. Bindstone with wackestone matrix from a patch reef in the Lower Cretaceous of South Texas. Massive coral framestone with wackestone matrix from a patch reef in the Lower Cretaceous of South Texas.

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