On May 7th I lead two fossil hunters to an accessible fossil locality in Murray County, Georgia. The locality is part of the Conasauga Shale Formation. This rock unit runs through Georgia, Alabama, and Tennessee. It is made of shales and mudstones that were deposited during the Cambrian Period (~541-485 million years ago). During this time, Northeast Georgia was under a shallow sea known as the Iapetus Ocean. This ancient sea was located deep in the Southern Hemisphere. Animals living in these waters included sponges, brachiopods, hyoliths, and the famous trilobites.
The most abundant fossils in this portion of the Conasauga Formation are the shed exoskeletons of trilobites. Trilobites are arthropods that were very common animals during the Paleozoic Era (~550-250 million years ago). The trilobites found in Murray County, Georgia died from rapid mudflows that came from a deep marine basin and anoxic (lacked oxygen) environment. Because of this, the trilobite fossils from this site are preserved very well and occur in body clusters with halos of iron oxide surrounding their bodies.
We began to plunge down a hill under a bridge where the outcrops are exposed to the surface. The exposures lie right near the Conasauga River (where the rock unit received its name). It didn’t take long to split the mudstone and come across the remnants of ancient Georgia’s inhabitants. The most common species of trilobite found in the outcroppings is Aphelaspis brachyphasis. They are so common that this locality has been referred to as the Aphelaspis Biozone. There are other species that were found such as agnostids like Glyptagnostus reticulatus which serves as an index fossil for the middle Cambrian and Agnostus inexpectans.
Agnostids are very small and only occur in rocks from the Cambrian and Ordovician period. Paleontologists have debated whether agnostids are even part of the class Trilobita at all. Agnostids had a head and a tail body parts with two or three thoracic segments. They also have have no eyes which suggest they lived in deeper waters where light did not penetrate the ocean. A lot of the trilobites that we found were disarticulated but some specimens recovered were complete molts. We all came back with well-preserved and numerous specimens.