Modeling fossil coral reefs to constrain sea level oscillations during the Last Interglacial maximum

Presented at BeGeo conference 2023 (3-6 October, Naples, Italy).Modeling fossil coral reefs to constrain sea level oscillations during the Last Interglacial maximumDenovan Chauveau1, Alessio Rovere1, Patrick Boyden2, Nikos Georgiou1, Ciro Cerrone1, Giovanni Scardino3,4, Silas Dean11Dipartimento di Scienze Ambientali, Informatica e Statistica Università Ca’ Foscari Venezia, Italy2MARUM – Center for Marine Environmental Sciences, University of Bremen, Germany3Department of Earth and Geoenviromental Sciences, University of Bari Aldo Moro, 70125 Bari, Italy4Interdepartmental Research Center for Coastal Dynamics, University of Bari Aldo Moro, 70125 Bari, ItalyKeywords: #sealevel #coralreef #coastalgeomorphologyUnderstanding past sea-level (SL) oscillations is essential to gauge future patterns of SL rise in response to warmer climate conditions. Due to good preservation and dating of fossil outcrops, the Last Interglacial (LIG; ~122 ka ago and with a global mean SL 6-9 m above the present level) is one of the best climate analogs to study the existence of abrupt SL changes within interglacials. This, in turn, allows for the distinction between natural perturbations in SL and those due to human activity. However, the existence and magnitude of intra-LIG SL oscillations is a hotly debated topic. Some LIG coastal stratigraphic sequences, especially those stemming from coral reef terraces (CRTs), are characterized by abrupt shifts in geological facies or double/multiple stepped stratigraphies, which were hitherto interpreted as proxies for abrupt, intra-LIG SL oscillations. Here, we utilize a multi-model approach to investigate whether these geological formations have a eustatic or land motion origin. To do this, we simulate the processes and SL scenarios that may contribute to build such reef stratigraphies within two model environments: DionisosFlow software (i.e., a 3D forward stratigraphic model) and the code of Pastier et al. (2019; Geochemistry, Geophysics, Geosystems, 20(8); i.e., a kinematic model based on reef morphology). As input, we test a wide range for each CRT morphogenesis parameter (i.e., reef growth rate, marine erosion rate, rock foundation geometry, etc.) and SL scenario. We then compare modeled and observed stratigraphies, and investigate which parameter set, processes, and SL scenarios are most consistent with observations of multiple-stepped reef stratigraphies, particularly at sites in the Caribbean (Aruba, Bonaire, Yucatan and the Bahamas archipelago). Our results highlight that the morphology of CRT sequences provides fundamental observations to unravel past SL, including the possible intra-LIG SL oscillations, and that these are key to understanding the current SL rise.