The Ghar Lapsi limestones : sedimentology of a Miocene intra-shelf graben

Abstract

The Gnar Lapsi succession of west Malta developed during a Late Tortonian Early Messinian episode of tectonism associated with the Maghlaq Fault Zone. These syntectonic strata, Porites coral bioherms bioclastic packstones and wackestones, debris flow deposits and calciturbidites form a prism banked against the southwest- facing fault-line but are absent from the island of Filfla which lies about 4.5km to the

west. Faunal correlation is imprecise; however, the macro faunas and general foraminiferal micro faunas of the Porites bioherm show it to be correlated with the Tal-Pitkal Member (Late Tortonian). The overlying calciturbidites and debris flow deposits are part of the Gebel Imbark Member (Early Messinian). These strata are part of a half-graben fill which cuts the Miocene shelf between Filfla and the present Magnlaq cliffs of Malta. The absence of planktonic Foraminifera from the graben fill sequence and low percentages recorded from strata on Filfla island confirm that this structure was intra-shelf in origin rather than a shelf edge feature. Calciturbidite laminites and debris flow deposits, developed during the Lower Messinian, were deposited during a eustatic fall of Mediterranean sea-level concomitant with the Lower Evaporite Complex of Sicily.