The Sarmatian Carbonate Tempestites from Kaliakra Cape (NE Bulgaria) – a Real Risk to Its Stability

Abstract

This study presents the results of 227 tested specimens of the Sarmatian age taken from the rock complexes that build Kaliakra Cape: these are carbonate tempestites, as well as the limestones from the Karvuna Formation lying above them. Sedimentological and geotechnical tests have been performed. 

The micropetrographic analysis of the carbonate tempestites is also presented, including slightly consolidated conglomerates and hard limestones between them. It was found that the matrix of conglomerates is composed mainly of micritic peloids. Their size is about and below 0.2 mm. No cement is found, which is why the porosity is significant. Peloidal limestone has low values of bulk density -- an average value of 1.95 g/cm³. There is a significant difference in compressive strength and velocity of seismic waves obtained in both directions -- crosswise and parallel to the layering. 

Studies of collapses in the caves in the area show that they occur in friable peloidal limestones, and the disturbances follow the formation. This is also confirmed by the laboratory tests of samples showing lower strength indicators, namely in the direction of the layering. The data thus obtained provide valuable information on the geotechnical parameters of the main varieties in which the rock deformations are developed, which can be used in the analysis of slope stability.