Abstract
The study of past sea levels relies largely on the interpretation of sea-level indicators. Palaeo tidal notches are considered as one of the most precise sea-level indicators as their formation is closely tied to the local tidal range. We present geometric measurements of modern and palaeo (Marine Isotope Stage (MIS) 5e) tidal notches on Bonaire (southern Caribbean Sea) and results from two tidal simulations, using the present-day bathymetry and a palaeo-bathymetry. We use these two tools to investigate changes in the tidal range since MIS 5e. Our models show that the tidal range changes most significantly in shallow areas, whereas both, notch geometry and models results, suggest that steeper continental shelves, such as the ones bordering the island of Bonaire, are less affected to changes in tidal range in conditions of MIS 5e sea levels. We use our data and results to discuss the importance of considering changes in tidal range while reconstructing MIS 5e sea level histories, and we remark that it is possible to use hydrodynamic modelling and notch geometry as first-order proxies to assess whether, in a particular area, tidal range might have been different in MIS 5e with respect to today.
Highlights
The study of past sea levels relies largely on the interpretation of sea-level indicators
The coral ages can be correlated with those found along the north-eastern and eastern coast of Bonaire, that are constrained to Marine Isotope Stage (MIS) 5e through strictly reliable 230Th/U-ages of seven Diploria strigosa coral colonies collected at elevations between ~1.5 and ~5.5 m37–39
The stratigraphy of the Lower Terrace is very similar between the western coast and the north-eastern and eastern coasts, the only difference being the width of the fossil reef terrace, which is much larger on the eastern and northern, windward side of the island
Summary
The study of past sea levels relies largely on the interpretation of sea-level indicators. We present geometric measurements of modern and palaeo (Marine Isotope Stage (MIS) 5e) tidal notches on Bonaire (southern Caribbean Sea) and results from two tidal simulations, using the present-day bathymetry and a palaeo-bathymetry. We use these two tools to investigate changes in the tidal range since MIS 5e. The comparison of the geometrical properties of a modern and a MIS 5e notch can give a first estimate on possible changes in the tidal range between today and MIS 5e
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