A multi-analytical study of beachrock formation in Naxos and Paros Islands, Aegean Sea, Greece and their palaeoenvironmental significance

Beachrocks are coastal sedimentary formations, which are relatively quickly cemented through the precipitation of CaCO3. Beachrock formation is widespread in low latitudes (i.e. the Mediterranean coastlines) and the cementation process near the sea level can be a potentially fast procedure; therefore, beachrocks can be used as sea level indicators. However, in many studies, debate still exists regarding their depositional environment and their use as indicators for sea-level changes. This study focuses on the beachrocks of Naxos and Paros Islands, in central Cyclades, Aegean Sea (Greece), aiming to contribute to the further understanding of their formation mechanism and palaeoenvironmental significance. For this purpose, a multi-analytical approach was accomplished, with the use of microscopic investigation, scanning electron microscope, energy-dispersive x-ray spectroscopy, x-ray diffraction and x-ray fluorescence. Our analysis revealed that the beachrocks of Naxos and Paros Islands were primarily formed in an environment equally saturated by sea and fresh water, at the middle intertidal zone. Calcite supersaturation in the water along with the de-gas of pore CO2 and the microbial activity, which resulted to physicochemical precipitation of High Magnesium Calcite (HMC), were the main mechanisms contributing to their formation. Our study highlights how multi-analytical methods may be used for more precise sea level reconstructions using beachrocks.

Automated summary

This study focuses on the beachrocks of Naxos and Paros Islands in central Cyclades, Aegean Sea (Greece), using a multi-analytical approach to reveal their formation mechanism. The beachrocks in these islands were primarily formed in an environment saturated by sea and fresh water, at the middle intertidal zone, with the main mechanisms including calcite supersaturation, de-gas of pore CO2, and microbial activity resulting in physicochemical precipitation of High Magnesium Calcite (HMC). The study demonstrates how multi-analytical methods can be used for more precise sea level reconstructions using beachrocks.