Geological mapping reveals the role of rift Jurassic architecture in the dispersal of calciturbidites: new insights from the Central and Northern Apeninnes.

CIPRIANI ANGELO; CARATELLI MARTINA; MASSIMO SANTANTONIO

Congreso; William Smith Meeting ?Geological mapping:of our world and others?; 2021

The Geological Society

Geological field mapping of ancient carbonate rift-basin successions, taking advantage of a multidisciplinary approach which encompasses sedimentology, biostratigraphy and structural geology, is pivotal for reconstructing the interplay between depositional dynamics and synsedimentary tectonics in carbonate platform/basin systems. An outstanding example is offered by the Meso-Cenozoic Lazio-Abruzzo Carbonate Platform/Umbria-Marche-Sabina Basin system in Central and Northern Apennines (Italy). Starting from field mapping and the measurement of stratigraphic sections in key-areas of the basinal domain, a geothematic field-work aimed at i) reconstructing the Tethyan Jurassic, rifting-related, depositional architecture characterised by a complex pattern of intrabasinal morpho-structural highs (pelagic carbonate platforms) and intervening deeper-water basins, ii) tracing the itineraries followed by sediment gravity flows shed by the margins of the neighbouring Lazio-Abruzzo Carbonate Platform and recorded in the pelagic succession, and iii) assessing the role played by the Jurassic submarine topography in funnelling and diverting the neritic material travelling across the basin. In order too meet these goals, the identification in the field of exhumed palaeoescarpment tracts bordering pelagic carbonate platforms is mandatory,. since field evidence indicatesthat the horst-block margins formed obstacles to the gravity flows as sediment load was discharged in confined basins at their toes. In some cases, depending on their orientation with respect to the main paleoflow axes, palaeoescarpments caused the partial or total deflection of turbidity flows, as highlighted by turbiditic deposits running parallel to them and the occurrence of sedimentary structures migrating upflow. While turbidity currents were locally vigorous enough to climb the escarpments, leaving overbank deposits on the pelagic carbonate platform-tops, a ?shelter? effect is evidenced by the resediment-free nature of those basins lying downflow, which were shielded by the intrabasinal highs.