?Siderastraea silecensis

Phyulm Cnidaria
Class Anthozoa
Order Scleractinia

 

(Scale Bar is 1 cm)

 

This species is one of a few corals found in the Neogene rocks near Valdosta. The corals were preserved in a two step, destructive fashion. Because the colonial skeleton is made of aragonite, corals are usually preserved as molds, the skeleton itself having dissolved away. The Neogene corals in south-central Georgia began being preserved in this way, but after and/or contemporaneous with dissolution the cavities were filled, from the edges inward, with microcrystalline quartz (chert). This preserved some semblance of the original structure of the colony. The figured specimen is typical in that so little detail of the individual animals' openings were preserved to preclude certain identification (left hand image above, of the top of a colony). On the other hand, the replacement did preserve the outlines of the original tubes in cross-section (right hand image above, of the broken side of a colony). The centers of the preserved fossils are often hollow, with linings of fine brown quartz crystals, in the fashion of geodes.

The ~2 cm round hole you can see part of near the bottom left side of the right hand image is the boring of a large Lithophaga (press "BACK" on your browser to return here from the Lithophaga page).

Because the corals are preserved as poorly they are, because they are only found in one small area, and because they presumably required a specific environment, they are probably not the best of guide fossils. However, they are similar to corals found preserved in a similar fashion in the Tampa Bay area of Florida, and strongly suggest that the rocks of the two regions are correlative.

Like most corals, these probably required shallow, rather clear open marine water. That they are not more widespread is probably a consequence of the dominance of southern Georgia by clastic sediments during this time.


AGE: MIOCENE (probably Early)

FORMATION: HAWTHORNE GROUP

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