- The Territory -
Brief geological history of the Sorrentine Peninsula
by Salvatore Palomba
- Part I -
Since the beginning of the19th century the Sorrentine Peninsula has been the subject of thorough studies by many experts interested exclusively in the geological characteristic of the area. Geological studies continued throughout the 20th century and developed in relation to the most modern theories on movements of the Earth’s crust.
Naples University researchers, who since the 1960s have been at the forefront of studies and understanding of phenomena leading to the formation of the Southern Apennines, have provided a significant contribution and important impetus to an awareness of Sorrento Peninsula geology.
At present the Sorrentine Peninsula is included in the Monti Picentini-Monti Lattari structural stratigraphic unit, and the highest section in the stratigraphic succession peaks here in the area concerned, characterised overall by a continuous series of dolomitic limestone dating from the Late Triassic to Late Cretaceous periods (195-65 million years ago).
As already mentioned, the Sorrentine Peninsula geological history begins about 200 million years ago at the end of the Triassic period when the huge continent known as ‘Pangea’ began to split into two large continental masses: Laurasia (North America + Eurasia) in the northern hemisphere and Gondwana (South America + Africa) in the southern hemisphere, separated by an expanding ocean known as Tethys.
Formation of the Continents (graphic animation)
During the Jurassic period (195-140 million years ago), the Tethys ocean, which basically extended from east to west, its axis located in proximity to the equator and constantly expanding, had a typical underwater landscape composed of extensive shallows (known as “carbonate platforms”, similar to current-day coral reefs) in which frame-building organisms regularly deposited calcareous sediments, alternating with deep oceanic basins.
The Italian mountain chains originated from these huge coral reefs and the sediments deposited in basins between.
In particular, in the Campano-Lucano section of the Apennines, at least three carbonate platforms have been recognised (recent studies suggest that the platforms from which the Southern Apennines originate could be more, at least seven separated by a similar number of basins) and sediments surfacing to form the Sorrentine Peninsula (Monti Lattari) are unanimously and in any event attributed to the westernmost platform, in literature normally referred to as the “Campano-Lucana”.
In this particular marine environment, organic sedimentation continues throughout the Cretaceous period (from 140 to 65 million years ago), accumulating an enormous sedimentary mass, which currently form a continuous dolomitic limestone series with a thickness of at least 4000 metres.
However, beginning already in the Late Jurassic period and continuing in the Cretaceous period, the ocean until then in expansion inverts its movement. The edges of the two continents begin to move closer, and this phenomenon causes compression of the great marine basin sediments, their folding and in some cases emersion; the tectonic process that will lead to formation of the Apennines and Alps chains has begun.
Initially, this occurrence does not affect our carbonate platform, in which, as mentioned above, organic sedimentation continues in an unchanged marine environment.
The Campano-Lucana platform will be affected by tectonic movements only at the end of the Cretaceous period and, as a result of the tremendous thrust, it will surface almost totally, migrating towards the basin centre and overlapping the deepest marine sediments.
The most recent limits of the dolomitic limestone succession surfacing in the Sorrentine Peninsula date back to the Late Cretaceous period as proof of this phenomenon.
From this moment onwards, for about 30 million years, these sediments will remain beyond the marine domain, and prevalent phenomena will be erosive whilst compression movement will continue to lead to superimposition and overlap of all sediments deposited in the ancient ocean.