Malta Geology

By | December 26, 2021

The islands of the small archipelago are made up almost exclusively of marine sediments of the lower and middle Miocene, only with small strips of terrestrial deposits of the Quaternary. The base of the stratigraphic series is formed by nulliporic and coralligenous limestones (“lower coral limestones” by the authors), which contain Foraminifera (eg. Lepidocyclina dispansa Mantelli), Mollusks (eg. Pecten Pasinii) and Echinids (eg Scutella striatula, Echinolampas posterolatus). They refer to the Aquitanian plan. These limestones assume the greatest development on the surface only to the NW. of Valletta between Musta and the Maddalena Bay, in the rest they emerge on narrow surfaces along the coastal margins of both Malta and Gozo, remaining engraved for considerable thickness (150 m. in certain points).¬†For Malta geography, please check franciscogardening.com.

Above the lower coralligenic limestones, and for a maximum power of 80 m., There are other limestone, sometimes marly, known under the name of “calcari a Globigerine” (see ocean). Above all, Microforaminifera and Echinides abound (eg Opissaster Scillae, Schizaster Parkinsoni, Eupatagus melitensis) and there are teeth of Selaci and remains of Turtles and Cetaceans (Rhocodon Scillae). As coming from globigerine limestones, remains of Ichthyosaurs and Mastodon angustidens are also reported.

By extension these globigerine limestones represent the most developed formation, occupying about two thirds (central and eastern parts) of Malta and a good half (SW and NW parts) of Gozo. Deposits of phosphatic nodules are present at various levels.

Clays and turquoise marls, Schlier type, lie on the previous limestones. They are rich in Microforaminifera and contain Echinides and numerous Molluscs (eg Pleurotoma cataphracta, Pecten denudatus, Vaginella Calandrellii, Aturia Aturi). They have a thickness of 10 to 12 m. and only occur in narrow outcrops in Malta (in the last western third), while they are fairly developed in Gozo. The complex of globigerine limestone and turquoise clays can be traced back to the Langhiano.

Followed by greenish glauconiferous sandstones, with a maximum power of about fifteen meters, sometimes absent. In Malta they are observed almost only along the rocky slopes of the western coasts, in Gozo in the central and western parts. They contain Eterostegine, Echinides (eg Clypeaster marginatus, Echinolampas Wrighti) and Mollusks (Proto cathedralis, Pecten Tournali, Cardium hians, etc.). They represent the lowest part of the Middle Miocene, i.e. the Elvezian.

The marine series ends with a limestone formation 100 meters thick and more called by the authors “superior coral limestone”. It is rich in Nullipore, Microforaminifera, Corals, Echinides (eg Cidaris melitensis, Clypeaster altus, Schizaster Scillae) and Mollusks (eg Turritella vermicularis, Pecten latissimus, Cardita Jouanneti). This limestone, which refers to the Tortonian plain, forms the largest part of the western third of Malta, constituting the highest parts such as the hills of Bengemma (239 m) and S. Maddalena (258 m), all of Comino and the tiny Filfola, and about a quarter (section E.) of Gozo.

In addition to those described, there are no other formations of marine origin, from which it appears that already in the upper Miocene the Maltese islands had emerged from the sea. Meteoric degradation and the millenary work of torrential waters, demolishing the Miocene rocks and transporting their debris, have produced coarse or minute alluvial sediments, sometimes terraced and sometimes cemented, as well as groundwater coatings and deposits filling karst cracks and caves. The most extensive alluvial strips are observed between Curmi and Casal Paola, in the Saline valley and along the Wied tal Puales and Wied tal Mistra, all in Malta.

Within all these continental formations, essentially attributable to the Quaternary, also copious remains of mammals, reptiles, birds and terrestrial molluscs were found. Among the most characteristic elements of this faunal association should be mentioned dwarf elephants of three breeds (Elephas Mnaidrae, E. Melitensis, E. Falconeri), gl’ippopotami (H. Amphibius pentlandi and a dwarf race), a giant dormouse (leithia melitensis), cranes, swans, tortoises, etc. There are also leftovers of deer and ox, attributable to a more recent horizon than the “hot fauna” to which elephants and hippos belong. Unlike what is found in nearby Sicily, however, no sure indications of the presence of Paleolithic man associated with said leftovers of deer and oxen were still found in Malta. Among the most important ossiferous deposits are those of Benghisa and Mnaidra and the caves of Mahglak and Zebbug in the eastern part of Malta and the caves of Melleha and Ghar Dalam in the western part.

The general tectonic trend of the small archipelago is almost tabular sub-horizontal, with only one notable hint of inflection at the NW end. of Malta, where the layers slope towards Comino, thus bringing the upper coralligenous limestone into the sea. The dominant tectonic motif is given by a system of faults, for the most part oriented from SW to NE. The most important of Malta is the one that crosses the whole island, from Ras ir Raheb to the South. edge of the Maddalena bay, and is designated by the name of “great fault”. As a result of this, the third NO. the island remains tectonically lowered, so that the lower coralligenic limestones come in contact with the higher ones for a good distance.

A large fault also crosses Gozo near its extreme SE, bringing down the extreme part of the island tectonically, so that the section between this fault and the “great fault” of Malta forms a typical rift valley, resulting from a system of stepped faults that follow one another in the interval between the two main ones.

From the predominant trend of the strata, from the aforementioned tectonic accidents and from the nature of the geological formations, the Maltese islands portray their characteristic morphological features: largely sheer coasts (lower coral limestone and globigerine limestone), upper sections in plateau – isolated often in small elements – similar to Sardinian tuna fisheries. The general arrangement of the stratifications and the calcareous nature of the upper ones, have favored the formation of karst phenomena with the characteristic physiognomy of the landscape, where they are more intense and widespread.

As for the sedimentary formations, the geological constitution of the islands of Malta finds considerable confirmation in south-eastern Sicily where the deposits of the lower and middle Miocene have a predominant development, most of which (especially the regions of Modica and Ragusa) emerged from the sea at the same time as those of Malta. The faunal links between the Maltese islands and Sicily during the Quaternary are also very evident, since we find in both regions the same three races of elephants, the hippopotamus, the same giant dormouse, etc. From this and from the consideration that such a large population of large pachyderms, as indicated by the rich ossiferous deposits, could not have developed in such a restricted environment without large streams, also due to the way of life and food., the hypothesis that the small Maltese archipelago was part of a much larger land, and connected to, or very close to, Sicily appears justified. This land, whose existence appears to be indicated by some submarine banks, such as that of Medina, would have sunk between the Pleistocene and the Holocene.

Malta Geology