Geochemical survey in solution subsidence structures (dolines) : examples from the Maltese islands

Abstract

The goal of this dissertation is to provide scientific data on concentration of CO2 and its influences in the soils of solution subsidence structures (dolines) of the Maltese islands. This includes atmospheric CO2 concentration, pressure, elevation and landscape features of individual doline. For the fact that, the evolution of geology, geomorphology and landscape features, varies from doline to doline. The dolines were selected randomly both in Malta and Gozo in order to analyse the difference between inside soil CO2 concentration and the outside of individual doline, as well as to scrutinise the relationship/variations among all the dolines. These dolines are formed in karst landscapes owing to the chemical dissolution of limestone because the Maltese archipelago is formed from single sedimentary rock predominantly limestone. Maltese karst development is classified into three, known as limestone pavements, solution subsidence structures (dolines), and caverns. Limestone pavements are largely formed on lower and upper coralline limestone due to the presence of higher porosity than the other rock strata. Similarly, most of the dolines are created on upper coralline limestone whereas some of the eight selected dolines such as Il-Cirku and Dwejra are formed on globigerina and lower coralline limestone respectively. The geology and geomorphology of Maltese archipelago is responsible for the formation of Maltese dolines. Maltese rocks are divide into five layers known as Upper Coralline Limestone, Green Sand, Blue Clay, Globigerina, Lower Coralline Limestone, and Quaternary deposits of the most recent rock. These layers had been interrupted with the Maltese faulting systems. Hence, the dolines are related to the faulting processes. The formation and evolution of dolines in general depends on vegetation, hydrology, structure, lithology, relief, climate and time.