Petrological, mineralogical and geochemical characteristics of the globigerina limestone outcropping at fomm ir-Riħ, Malta

Abstract

Fomm ir-Riħ is a scheduled area on the western coast of Malta characterised by an unusual syncline and clay slopes. This article addresses the Globigerina Limestone formation, which outcrops at this site of geological interest. The Lower Globigerina Limestone, the oldest member of this lithostratigraphic unit, is absent. The matrix to allochems ratio of the Middle Globigerina Limestone is significantly different from that of the Upper Globigerina Limestone. In both, the matrix is composed of well-preserved micrite, rarely recrystallised to microspar. The petrology and mineralogy of the Middle Globigerina Limestone is similar to that of the blue lenticular patches occurring in the Lower Globigerina Limestone where it outcrops in other parts of the island, but geochemical data vary. The SiO2 content of the Middle Globigerina Limestone is < 20%, while in the case of the Upper Globigerina Limestone, it is > 20%. The SiO2, Al2O3 and Fe2O3 content increases gradually from the Middle to the Upper Globigerina Limestone member.