Upper Jurassic caryophyllids from condensed pelagic deposits of the Umbria-Marche Apennine (Central Italy)

FABBI, SIMONE; ROMANO, MARCO; LATHUILIÈRE B.; CIPRIANI, ANGELO; CITTON, PAOLO

Congreso; 2nd Palaeontological Virtual Congress; 2020

Here we report newly collected corals from Kimmeridgian?Tithonian pelagites of Central andNorthern Apennines. They grew on intrabasinalstructural highs (Pelagic Carbonate Platforms orPCPs). The highs originated from dismemberingand drowning of a vast peritidal carbonate platformduring the Early Jurassic Western Tethysrifting stage. The drowning was followed by condensedpelagic sedimentation on the top of PCPs.Findings of both zooxanthellate and probablyazooxanthellate corals in these facies shed newlight on the Jurassic-Early Cretaceous paleogeography,paleoenvironment and paleoecology ofPCPs. The occurrence of zooxanthellate corals inPCP-top condensed successions recently allowedto constrain the bathymetry of these depositionalsystems to the photic zone (40 ? 150 m). Thestudied material is mostly represented by solitary,probably azooxanthellate corals, associatedwith light dependent organisms. These specimensusually display elliptical to circular calices􀁄􀁑􀁇􀀃􀁋􀁄􀁙􀁈􀀃􀁆􀁈􀁕􀁄􀁗􀁒􀁌􀁇􀀃􀁄􀁗􀁗􀁄􀁆􀁋􀁈􀁇􀀃􀁐􀁒􀁕􀁓􀁋􀁒􀁏􀁒􀁊􀁌􀁈􀁖􀀏􀀃􀈴􀁑􀁈􀁏􀁜􀀃granulated costosepta with a clear crown of palis.Pending a more detailed study of their microstructure,these features suggest an assignationto the scleractinian extant family Caryophyllidae.The collected azooxanthellate fauna is oligotypicbut abundant, as a possible result of very slowsedimentation rates and extreme condensation.Most of the corals do not display in-life position,being detached from the substrate and randomlyarranged within the pelagic deposits; others areattached on ammonites pseudoshells or on othercorals. The new occurrence improves the LateJurassic record of caryophyllids, providing additionalconstraints on their paleoecology and onthe paleoenvironmental evolution of this sectorof Western Tethys.