On the origin of the calciturbidites in the Tortonian hemipelagic marls of the Latium-Abruzzi carbonate platform domain (Central Apennines, Italy); tectonic, sea level changes or internal waves?

Abstract This study focuses on the calciturbidites within the Orbulina Marls unit, Tortonian to early Messinian in age. Classically, the composition of calciturbidites provides valuable insights into the depositional system of the source area, the loci of accumulation, the depositional processes, and the factors that influence sedimentation. This work investigates the source and discusses the triggering mechanism behind the deposition of Tortonian, platform-derived, bioclastic intercalations found within hemipelagic deposits of the Latium Abruzzi Domain (Central Apennines). These intercalations are interpreted as the result of turbidity currents. Two distinct types of intercalations were distinguished. The first exhibits a diverse skeletal assemblage comprising oligophotic and aphotic organisms, while the second consists solely of planktonic biota. The presence of these intercalations within deep, hemipelagic deposits indicates the existence of an active carbonate ramp, characterized by extensive oligophotic and aphotic facies belts, during the Tortonian. Turbidites can be triggered by many mechanisms. In this case the sedimentation of these deposits has been attributed to the influence of internal waves. The latter break where they intersect the substrate, in correspondence of the oligophotic middle ramp, generating an upslope current first, and a downslope return flow later, tractive and/or turbulent. These waves emerged due to the development of a robust pycnocline, sustained by Late Miocene global and regional climate changes that led to pronounced stratification in the water column due to heightened thermal and density gradients.