SEA TURTLE NESTS INCREASE COMPLEXITY IN POST-HURRICANE BARRIER LITHOSOMES

Along many coastlines of the world, vertebrates (e.g., chelonians, pinnipeds, penguins) and macroinvertebrates (e.g., decapods) produce diverse suites of traces that reach into zoogeomorphic scales (decimeters to meters). Pinniturbation (substrate reworking by flipper action) extends from low (sea turtles) to high-latitude (pinnipeds) shorelines. The former produce complex traces (polychresichnia): approach/egress crawlways (repichnia), trial/abandoned excavations, and eventual compound body pit + egg chamber + cover pit structure (calichnia). During incubation, predation by mammals, birds, and crustaceans may produce overprinting (praedichnia), with the cycle culminating in hatchling escape or burial (fugichnia/taphichnia). Depending on turtle species (estuarine/marine), nest structure may affect from ~1 to >5 m³ of sediment (e.g., leatherbacks) and philopatry ensures that millions of nests remain preserved in prograded coastal sequences, mostly swales and aeolian ramps within strandplains. In 2D cross-sections or geophysical images, nests may closely resemble storm-surge scour structures. Along the Florida Gulf Coast barrier islands, nests of green (Chelonia mydas) and loggerhead (Caretta caretta) sea turtles have been imaged with high-frequency (500-800 MHz) ground-penetrating radar (GPR). A recent increase in the number of loggerhead nests following an intense storm (Hurricane Ian, 2022) allows assessment of the complexity of biogenic bedding, which is sometimes adjacent to partially buried hurricane ebb-surge channels. The latter appear as cut-and-fill structures in GPR images and may be potentially confused with large nests. Imaging of post-hatch nests is especially critical for documenting the diversity and diagnostic signatures of ichnites that will be preserved through progradation and aeolian deposition. Neoichnological research of nest sites is underway to assess their: 1) indicative meaning (shoreline position and orientation, tide-mediated water table); 2) paleo-ichnological framework to improve discovery in the rock record (ichnotaxonomy, ichnocoenoses, ichnofabrics); 3) geophysical signatures (geoclutter); 4) archaeological context (site selection and resource use by maritime cultures), and 5) conservation of endangered species.