BRIDGEBORO LIMESTONE
EARLY OLIGOCENE (RUPELIAN or VICKSBURGIAN)
The Bridgeboro Limestone crops out in a broad band along the northwest flank of the Pelham Escarpment between Dublin and Bainbridge, and continues into Florida. It is very easy to recognize, being dominated by algal rhodoliths packed densely together, as seen in the photos above. There are beds of algal sand with few rhodoliths, but they comprise a small part of the unit.
The Bridgeboro is also known from the subsurface south and east of the Pelham Escarpment, where it is covered by the Neogene sediments of the Tifton Upland. It occurs as a pair of bands flanking an old deepwater channel called the "Suwannee Strait" or "Gulf Trough".
The rock type, the abundance of red algae, and the paleogeographic position of the Bridgeboro along the shallow edges of the Suwannee Strait leads to the interpretation of the rock as an old shelf-edge limestone facies. Early workers reported abundant coral reefs in the unit near Bainbridge, which would be expected in a shelf-edge deposit. Unfortunately, these exposures are now covered by Woodruff Lake.
In addition to the rhodoliths (mostly Archaeolithothamnium sp.), there are abundant and diverse other fossils in the Bridgeboro. You may choose from this list to see photos of some of them:
KINGDOM PROTISTA
DIVISION RHODOPHYTA
PHYLUM PROTISTA
KINGDOM ANIMALIA
PHYLUM MOLLUSCA
CLASS GASTROPODA
CLASS BIVALVIA
PHYLUM ECHINODERMATA
CLASS ECHINOIDEA
ORDER CASSIDULOIDA
ORDER CLYPEASTEROIDA
ORDER SPATANGOIDA
PHYLUM CHORDATA
CLASS CHONDRICTHYES