5th UF Water Institute Symposium Abstract

Submitter's Name Karen Vyverberg
Session Name Sea Level Rise: Projections and impacts
Author(s) Karen Vyverberg,  Department of Geological Sciences, University of Florida, Gainesville, Florida, USA (Presenting Author)
  Belinda Dechnik,  Geocoastal Research Group, School of Geosciences, University of Sydney, Sydney, NSW, Australia
  Andrea Dutton, Department of Geological Sciences, University of Florida, Gainesville, Florida, USA
  Jody M. Webster, Geocoastal Research Group, School of Geosciences, University of Sydney, Sydney, NSW, Australia
  Dan Zwartz, Antarctic Research Centre, Victoria University of Wellington, Wellington, New Zealand
  Coral reef response to global sea-level change during the previous interglacial period
  Characterizing the evolution of global mean sea level (GMSL) during warm periods is critical to constraining the dynamic response of the large polar ice sheets to different climatic drivers and can facilitate efforts to identify and understand those forcing mechanisms. The non-linear retreat and/or regrowth of ice sheets in the future would necessitate sophisticated adaptation measures to preserve coastal resources such as habitable living space, potable water, and ecosystems. Reconstructing the course of GMSL during a previous interglacial with a similar ice sheet configuration as today, such as Marine Isotope Stage (MIS) 5e (~129,000 – 116,000 years ago), can improve our understanding of the response, and so potentially drivers, of ice sheet and sea-level change. Because sea-level position is a primary control on coral reef morphology and composition, identifying changes in these parameters in fossil reefs can inform reconstructions of past sea-level behavior. Here we provide a detailed examination of MIS 5e fossil reefs located in the granitic Seychelles that record sea-level changes from ice-volume contributions. To reconstruct relative sea level (RSL), we combine elevation surveys with sedimentary and taxonomic examinations. At all sites we observed a similar pattern of outcrop architecture of two or three discontinuous reef growth units, which suggests a common sea-level history. In each limestone buildup, primary coralgal colonization is disconformably capped by (i) reef rubble, (ii) a Pyrgomatid barnacle-bearing micrite, and/or (iii) a reef unit with different taxa. This first package is repeated at least once more in each outcrop. Additionally, we identified four different fossil coralgal assemblages that correspond to modern communities with distinct water-depth habitats allowing for direct inferences of paleo-water depth at different phases of reef growth. The robust reef history we have in the Seychelles provides a strong control on the sea-level historyduring MIS 5e.