Clastic sedimentary features of beachrocks and their palaeo-environmental significance: comparison of past and modern coastal regimes

Clastic sedimentary features of beachrocks and unconsolidated deposits of parent beaches were investigated along the northern Aegean coastline (Greece) to assess their suitability in palaeo-environmental reconstruction. Twelve paired datasets were collected in the Thermaikos, Toroneos, Siggitikos and Ierissos gulfs of the Chalkidiki Peninsula, the adjoining Kavala Gulf and Thassos Island, comprising beachrock cores and companion beach subsurface sediments. Particle size analyses based on univariate and bivariate statistics suggest that, during the time period of beachrock formation, depositional conditions differed distinctly from those of the modern parent beaches. The results imply difference of maturity level of beach evolution from the time of cementation (coarser materials-early stage of beach formation) to modern situation (finer materials-reworked and ‘mature’ beach sediments). Furthermore, the findings indicate increasing coastal protection due to beachrock exposure in the modern swash zone. In conclusion, it is suggested that textural analysis of beachrocks in comparison with unconsolidated sediments of the parent beach might provide information regarding differences of coastal depositional regimes and future research could focus on specific-layer analysis and comparison.