Submerged Speleothems and Sea Level Reconstructions: A Global Overview and New Results from the Mediterranean Sea

Fabrizio Antonioli,Franco Foresta Martin,Edwige Pons-Branchu,Stefano Furlani,Valeria Vaccher,Paolo Montagna,Lucio Calcagnile,Jonathan Cecchinel,Maurizio Gasparo Morticelli,Valeria Lo Presti,Paolo Stocchi,Gianluca Quarta

doi:10.3390/w13121663

Abstract

This study presents a global overview of the submerged speleothems used to reconstruct paleo sea levels and reports new results from two stalactites collected in the Mediterranean Sea. Coastal cave deposits significantly contributed to the understanding of global and regional sea-level variations during the Middle and Late Quaternary. The studied speleothems cover the last 1.4 Myr and focused mainly on Marine Isotope Stages (MIS) 1, 2, 3, 5.1, 5.3, 5.5, 7.1, 7.2, 7.3 and 7.5. The results indicate that submerged speleothems represent extraordinary archives that can provide detailed information on former sea-level changes. The two stalactites collected in the central Mediterranean Sea, at Favignana and Ustica islands (Sicily, Italy), are both characterized by continental, phreatic or marine layers. The U-Th and 14C ages of the new speleothems provide results of great interest for relative sea-level changes over the last 1000 years.

Highlights

The study of submerged speleothems in coastal caves significantly contributed to explaining past sea-level variations for the last 1.4 Myr, especially for the climaticallyimportant Marine Isotope Stages (MIS) 1, 2, 3, 5.1, 5.3, 5.5, 6.5, 7.1, 7.2, 7.3 and 7.5
The Western North Atlantic–Caribbean region, and Bermuda in particular, is strongly affected by the vertical motions of the periglacial forebulge that formed as a result of upper mantle flow in response to the expansion of the Laurentide ice sheet during glacial periods
As the three ice-sheet models are all somehow tuned to the δ18O stack curve, we suggest that their volumes might be biased towards larger values, while the speleothems described here might require a volume reduction throughout the MIS 3, which would result in a much higher eustatic level

Summary

Introduction

The study of submerged speleothems in coastal caves significantly contributed to explaining past sea-level variations for the last 1.4 Myr, especially for the climaticallyimportant Marine Isotope Stages (MIS) 1, 2, 3, 5.1, 5.3, 5.5, 6.5, 7.1, 7.2, 7.3 and 7.5. Submerged speleothems can be dated using the U-series disequilibrium methods that provide precise and accurate age determination e.g., [1,2,3,4,5] These carbonate deposits are usually found in caves that are currently below sea level and flooded, and they often contain marine layers/encrustations or growth hiatuses that identify periods of highstands when the seawater invaded the cave and reached the speleothem. Other biological–physical markers have been used to reconstruct past sea-level variation including shallow-water corals, lagoonal and marine cores, tidal notches, and archaeological remains that are well connected to sea-level fluctuations Most of these indicators exhibit large uncertainties in age determination due to sample alteration and/or in absolute elevation (e.g., paleowater depth for corals). In the Mediterranean Sea, more than 300 submerged speleothems were sampled in 32 caves and more than half were analyzed for paleo sea-level reconstructions (Figure 1) [6]

Methods

Results

Discussion

Conclusion