Poster:
AAPG – Granda, Spain, 5-18 March 2018. Session 4 : Extension and Hyper-extension in the Mediterranean.
Authors:
Romain Pellen, Speranta-Maria Popescu, Jean-Pierre Suc, Marina Rabineau, Mihaela-Carmen Melinte-Dobrinescu, Daniel Aslanian, Jean-Loup Rubino, William Cavazza.
Abstract:
The Adriatic Basin (Central Mediterranean Sea) is the place of intense controversy concerning the sedimentary dynamics and palaeogeographic evolution during the Neogene, especially during the Messinian Salinity Crisis (MSC: 5.97 to 5.46 Ma). Following the various interpretations, this basin was totally disconnected or connected to the deep basins during the Messinian Salinity Crisis. Sediments deposited in the Apennine foredeep after the peak of the MSC are hihgly debated about this main problematic on both chronostratigraphic and palaeoenvironmental grounds.
We performed calcareous nannofossil and dinoflagellate cyst analyses on five sections along the Apennine foredeep (Monticino, Maccarone, Civitella del Tronto, Fonte dei Pulcini, Fonte la Casa). The studed interval belongs to the p-ev2 (post-evaporitic) Formation that includes the Colombacci deposits, emblematic of the Lago Mare in the area. Marine microfossils recorded in previous studies have often been neglected or considered reworked and hence discarded. We propose the occurrence of at least four marine inflows between 5.36 and 5.33 Ma, each of them being indicated by marine dinoflagellate cysts that are rapidly replaced by Paratethyan (brackish) ones.
From this perspective, the Apennine foredeep is to be considered an isolated perched basin during most of the peak of the MSC (5.60–5.46 Ma), which was progressively and repeatedly invaded by marine waters overflowing a palaeo-sill before the beginning of the Zanclean (5.33 Ma) consistently with the global continuing eustatic rise.
Additional multiscale approaches (seismic and well studies, field data) of the sedimentary filling were used to highlight the tectono-stratigraphic evolution around the Gargano Peninsula (i.e. the Pelagosa palaeo-sill). Analysis of the Tertiary sedimentary megasequences allows us to identify several depocenters along the Apennine Chain and South Adriatic Basin. These observations emphasize the crucial role of the Mesozoic carbonate platforms and basins and the Apennine Chain formation in the palaeogeographic evolution of the Adriatic domain. The Messinian time appears to have been a crucial period for the uplifting Apulian-Gargano-Dinaride composite threshold.
As main result, we show that the Lago Mare facies cannot be restricted to a single brackish palaeoenvironment but must be understood as competing marine and brackish waters controlled by physiographic factors. The Mesozoic heritage with the Apennine front propagation plays a major role in the palaeo-environmental evolution of the Apennine foredeep. Deposits overlying the unconformity separating the regional p-ev1 and p-ev2 formations must henceforth be regarded as representing the first marine incursion into the isolated central Adriatic Basin after the peak of the MSC. These results allow us to refine the palaeogeographic reconstruction of the Apennine foredeep during the peak of the MSC. Although this basin was deep, its history during the peak of the MSC did not parallel that of the central Mediterranean basins.
