Constraining sea level variations in the Last Interglacial by modeling fossil coral reefs: A step forward in understanding the current rise?

The morphology of fossil coral reef (FCR) sequences provides fundamental observations to unravel past sea levels (SL), including the possible intra-Last Interglacial (LIG) SL oscillations, and thus to anticipate future variations. For that purpose, converting morphometric observations into SL datum requires understanding the FCRs morphogenesis. The FCRs sequence at Cape Laundi (Sumba Island, Indonesia), commonly serves as a benchmark. Previous authors identified at least three distinct FCRs associated with the LIG. Thus, to understand the morphogenesis of this multiple record, we numerically model the growth of the sequence, testing a range of SL curves (with one or several SL peaks at the LIG). Our results suggest that, regardless of the SL curves used, 1) the lowermost FCR was first carved during the LIG marine transgression and was later reshaped during the LIG marine regression, and 2) the intra-LIG SL variations are not the main reason for the several LIG FCRs observed in the sequence (the older FCRs being the main cause). But this may not be the case on other sites in the world (e.g., Bahamas). Therefore, we propose to try our numerical approach to discern between an eustatic vs non-eustatic origin of the ‘double-stepped’ stratigraphy of other LIG FCRs.