The Use of Submerged Speleothems for Sea Level Studies in the Mediterranean Sea: A New Perspective Using Glacial Isostatic Adjustment (GIA)

Fabrizio Antonioli,Paolo Stocchi,Paolo Montagna,Stefano Furlani

doi:10.3390/geosciences11020077

Abstract

The investigation of submerged speleothems for sea level studies has made significant contributions to the understanding of the global and regional sea level variations during the Middle and Late Quaternary. This has especially been the case for the Mediterranean Sea, where more than 300 submerged speleothems sampled in 32 caves have been analysed so far. Here, we present a comprehensive review of the results obtained from the study of submerged speleothems since 1978. The studied speleothems cover the last 1.4 Myr and are mainly focused 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 reveal that submerged speleothems represent extraordinary archives providing accurate information on former sea level changes. New results from a stalagmite collected at Palinuro (Campania, Italy) and characterized by marine overgrowth are also reported. The measured elevations of speleothems are affected by the local response to glacial and hydro-isostatic adjustment (GIA), and thus might significantly deviate from the global eustatic signal. A comparison of the ages and altitude values of the Mediterranean speleothems and flowstone from the Bahamas with local GIA provides a new scenario for MIS 5 and 7 sea level reconstructions.

Highlights

The study of submerged speleothems in coastal caves has significantly contributed to constraining past sea level variations for the last 1.4 Myr
Results from the Marine Isotope Stages (MIS) 5.1 phreatic overgrowth on a speleothem (POS) samples in Mallorca agree with the finding of some deposits from the same age between +2 and +1.5 m near Gibraltar [98], but disagree with the following:
All the eustatic curves; The U-Th ages reported by [96] for Mallorca; The speleothem from Plemmirio located at −20.2 m [64]; The speleothems K-18 and K-14 from Croatia at −18.8 and −14.5 m; The DWBAH flowstone from Bahamas at −15 m (Figure 10); The morphology of the MIS 5.5 tidal notches [36] and the lack of younger tidal notches; The mushroom-like landforms with tidal notches at −25 m found on Tavolara island (Sardinia) and interpreted by [36] as being MIS 5.1 in age; The results of glacial and hydro-isostatic adjustment (GIA) of the Mediterranean Sea

Summary

Introduction

The study of submerged speleothems in coastal caves has significantly contributed to constraining past sea level variations for the last 1.4 Myr. Grand Bahama Island, and [9] interprets the origin of the encrustations from Cova de Sa. Bassa Blanca cave (Mallorca) as carbonate formations related to the Pleistocene sea level variations. Other studies used submerged speleothems to constrain relative sea level changes, taking advantage of the improvement of the U-series disequilibrium dating method by mass spectrometry for precise and accurate age determination, e.g., [1,10,11]. These carbonate deposits are usually found in caves that are below the sea level and presently flooded and they often contain marine layers/encrustations or growth hiatuses that identify periods of highstands, when the sea level reached the speleothem The importance of the sea level in controlling groundwater elevation in both inland and coastal karst was first proposed by [7], but it was only in the early 1970s that the potential of using speleothems to reconstruct former sea levels was fully recognized.

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Conclusion