The oligo-miocene sediments of the Maltese Islands

The Maltese Islands are situated at the south-western end of the Malta-Ragusa Rise, an area characterised by high gravity anomaly values and a ridge-like bathymetrical profile. The Islands lie 50-80km. south of Sicily and 282km. away from the north African coastline.The sedimentary sequence is entirely composed of shallow water carbonates, dominantly marine, and with biohermal developments in the upper and lower exposed formations. The intermediate formations accumulated in somewhat deeper water and are characterised by planktonic foraminifera.Subdivision of the Upper and Lower Coralline Limestone Formations into 7 new members and 11 new beds was found necessary, in order to appreciate fully the local environments represented in these shallow water units. The Globigerina Limestone and Blue Clay Formations are now considered as fairly shallow water deposits, the analysis of the associated phosphorite conglomerate beds of the former indicating that dominant transport of clasts was from the west, in an area of primary phosphorite and glauconite development. The Greensand Formation is re-defined on the basis of sedimentology, and the upper part of previous classifications is now included in the Upper Coralline Limestone Formation.For each of the Formations a total of 15 biofacies are proposed on the basis of faunal variation. The probable depth ranges of each are used to refine conclusions drain from the sedimentological interpretations, in order that the palaeoenviromnents may be reconstructed. The study of a newly defined brachiopod marker horizon within the Upper Corailine Limestone has resulted in the prediction of the ecology of the four species involved, primarily with the aid of bryozoan growth-form studies. A new fossil fish horizon in western Malta is also discussed.A number of tectonic structures previously referred to as "sinks" are re-defined, and a prolonged episode of Cainozoic cavern development, associated with subaerial and submarine subsidence is postulated on the basis of structural and sedimentological interpretations