The study of fossil assemblages and the response of marine ecosystems to dramatic oceanographic and climatic changes may provide insight into the vulnerabilities – and resiliency – of modern species and fisheries affected by climate change, ocean acidification, and overfishing.

The fossil record is our only window into faunal changes and biodiversity crises in the deep geological past. Fossil-rich strata in Charleston, South Carolina, preserve two unique time periods during the history of the Atlantic ocean and the evolution of its fauna:

1. The origin of the modern marine fauna as a response to the first Antarctic glaciation during the Oligocene epoch (30-23 mya)

2. The origin of modern species in the context of glacial/interglacial climatic fluctuations during the beginning of the ice ages (early Pleistocene, 1-2 mya).

The first of these critical periods, the Oligocene epoch, captures the dramatic radiation of cetaceans – which increased in diversity by tenfold when they diverged into toothed whales and baleen whales. The Charleston embayment captures this with nearly 30 species including toothed baleen whales (Coronodon), dwarf toothless suction feeding dolphins (Inermorostrum), giant killer dolphins (Ankylorhiza), the first echolocators (Xenorophus, Echovenator, Cotylocara) and the first filter feeding baleen whales (Eomysticetus, Micromysticetus). This diversification also led to diversifying sea turtles and the origin of the modern shark fauna. These evolutionary events are dramatic biotic responses to major changes in marine ecosystems including the first Antarctic glaciation in several hundred million years and a sudden influx of marine plankton. Similar fossil assemblages are known from New Zealand, Japan, and the Pacific Northwest, but none are so exceptionally rich as the Oligocene marine strata of Charleston.

The second of these time periods, the early Pleistocene (2.5 mya to 780,000 years), is globally under-sampled and poorly known. The Pleistocene is exceptionally well-studied in the context of land mammals and extinctions at the end of the ice age – but marine vertebrate faunas from this time are virtually unknown.

The early phases of glaciation at the beginning of the ice ages made the early Pleistocene far cooler than the preceding Pliocene. Marine vertebrates from the Pliocene include a wide variety of bizarre forms with strange adaptations (dwarf suction feeding baleen whales) or wildly different habitat tolerances in comparison to their modern relatives (e.g. subtropical walruses and belugas), and relatively few occurrences of modern genera or species. Middle and late Pleistocene fossils are nearly entirely modern – forcing these changes in the marine ecosystem to have occurred in the early Pleistocene. Was there an extinction event during the early Pleistocene? When exactly did modern species evolve or arrive in the North Atlantic? The Waccamaw Formation near Ridgeville, South Carolina, is perhaps the only fossil assemblage on earth that can shed light on marine ecosystem change during the early phases of the ice ages approximately 1-2 mya.