Coniacian-Santonian rudist facies in Cilento (southern Italy)

Riccardo Cestari, Jose Maria Pons

Research output: Contribution to journalArticleResearchpeer-review

7 Citations (Scopus)

Abstract

Limestones, which were deposited from the Triassic to the Palaeocene in the Mediterranean Tethys and belonging to the Apennine carbonate platform, crop out in Cilento (southern Apennines, southern Italy). This platform was buried by Palaeocene limestones and Miocene silici-clastic turbidites and the whole succession known as Apennine Unit was, later on and due to tectonics, covered by deep marine deposits of the Ligurid Unit, of western origin. The object of this study are the rudist facies, deposited in the area from the Coniacian to the Santonian (Late Cretaceous) and mainly constituted by lagoonal to peritidal limestones with diffuse radiolitid-dominated assemblages. Radiolitid bivalves were widespread, from the Turonian to the Santorian, in the inner facies of the Mediterranean intraoceanic carbonate platforms. Due to intrinsic palaeobiological reasons, still not well understood, individuals of this bivalve family were able to settle, as mono- to oligotypic assemblages, on subtidal to high-subtidal facies with medium to high sedimentation rate. Integrate macro- and microfossils analysis, considering together most recent knowledge on rudists and benthic foraminifers distribution, have been carried out in order to define a better rudist biostratigraphy of inner carbonate platform facies, that can be useful to recognise and to date the carbonate successions in the Apennine carbonate platform. Three sections have been sampled and studied in the area: Trentinara, Capaccio Vecchio and Raia del Pedale, that are located along the Vesole Mt. - La Raia del Pedale Mt. alignment. Two datum planes have been considered for correlation, the older one corresponds to the unconformity on top of the Cenomanian carbonates and breccias and the younger one to the unconformity characterised by the Upper Palaeocene-basal Eocene limestones transgression. Rudist assemblages, mainly of the radiolitid genera Biradiolites, Bournonia, Radiolites, Durania and Sauvagesia, which inhabited lagoonal to peritidal environments even subjected to high sedimentation rate, occur in the considered interval. Monotypic associations of the requieniid genus Apricardia characterise high-subtidal facies with low sedimentation rate. Hippuritid shell fragments occur in grain-supported deposits transported by storm processes from more open areas. Two main regressive sedimentary sequences have been recognised in the succession, the first one (CO Sequence) is developed in all the three studied sections and is composed of slightly dolomitised mud-supported limestone, of lagoonal to peritidal facies with mono- and oligotypic radiolitid assemblages, evolving to peritidal laminate facies. The macrofossil association is characterised by Biradiolites angulosus (D'ORBIGNY), Biradiolites martelli (PARONA), Radiolites trigeri (COQUAND), Durania arnaudi (CHOFFAT) and, in the upper part, by Bournonia gardonica (TOUCAS), and the microfossil association by Moncharmontia apenninica (DE CASTRO), Scandonea samnitica DE CASTRO and, in the upper part, scarce Accordiella conica FARINACCI and Dicyclina schlumbergeri MUNIER-CHALMAS. This assemblage is referred as CO assemblage of Coniacian age, although the Late Turonian can not be excluded, it corresponds to the K event in CESTARI and SARTORIO (1995) and to the foraminifer cenozone, in inner carbonate platform facies, of Accordiella conica and Rotorbinella scarsellai in CHIOCCHINI et al. (1994). The second regressive sedimentary sequence (SA Sequence) is composed of mud-supported facies, with frequent grain-supported biodetritic tempestite episodes, with mono- to oligotypic radiolitid assemblages organised in bouquets and limited thickets. These are specially well preserved at Trentinara where they change vertically, and laterally towards Capaccio Vecchio, to intertidal dolomitic facies, showing evidence of emersion with vegetal rhyzomi referred to terrestrial plants. The macrofossil association is characterised by Bournonia fascicularis (PIRONA), Radiolites dario (CATULLO). Sauvagesia tenuicostata POLŠAK and the microfossil association is similar to the lower one (CO Sequence) and, at the top, the presence of the Lake Santonian marker Keramosphaerina tergestina STACHE is documented.
Original languageEnglish
Pages (from-to)175-192
JournalCFS Courier Forschungsinstitut Senckenberg
Issue number247
Publication statusPublished - 19 Apr 2004

Keywords

  • Biostratigraphy
  • Coniacian-Santonian
  • Palaeotectonics
  • Rudists facies
  • Southern Italy

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