ICHNOLOGY AS A TOOL FOR UNDERSTANDING ECOLOGICAL AND GEOLOGICAL CHANGES OF THE GEORGIA BARRIER ISLANDS

Ichnology – the study of modern and fossil organismal traces – is a science that neatly intersects with ecology and geology. For example, ichnologists often consider how the mass effects of bioturbation, bioerosion, and other tracemaking activities influence or shape entire ecosystems (e.g., burrowing and biodeposition of sediments), or how suites of trace fossils (ichnofacies) reflect biotic and abiotic factors in past ecosystems. Nonetheless, ecologists and geologists who study barrier-island systems may fall into a disciplinary trap that separates their respective studies. We hope to encourage unifying these sciences via ichnology, while offering Georgia barrier-island systems as logical venues for such alliances. After all, the Georgia coast is where foundational principles of modern ecology were born in the 1950s and 1960s, as well as neoichnological studies in the 1960s applied to interpret ancient shorelines in the Lower Coastal Plain of Georgia. Later geologists working in the 1970s and 1980s firmly established the Georgia coast and their traces as modern analogs for ichnofacies and trace fossils worldwide. As for now and the near future, we can use ichnology to predict future ecological and geological changes on the Georgia coast. For instance, sea-level rise should cause laterally adjacent trace assemblages to succeed one another vertically, particularly from more frequent (and ferocious) tropical storms. Different suites of tracemakers should colonize sandy storm-washover deposits lying above former salt marshes, quickly replacing ecosystems. Accelerated erosion of coastal dunes from storms will also negatively impact shorebirds and sea turtles that use these environments for nesting. Burrowing and biodeposition rates in Georgia salt marshes may also shift with rising sea level and water temperatures. Although freshwater ichnology was neglected in previous decades, the shifting hydrology of the Georgia barrier islands – particularly from saltwater intrusion – will be recognizable in a future geological record through traces made by terrestrial plants, crayfishes, insects, amphibians, and alligators, all of which cannot tolerate higher salinities. In short, we expect that ichnology will remain a useful science for ecologists and geologists alike going into the rest of the 21st century.