Fold uplift and synkinematic stratal architectures in a region of active transtensional tectonics and volcanism, eastern Tyrrhenian Sea

Abstract

The detailed stratigraphic analysis of synkinematic stratal architectures permits the calculation of fold uplift rates and the reconstruction of fold kinematics. This approach was applied to active folds in the Bay of Pozzuoli, eastern Tyrrhenian Sea. This area features late Quaternary volcanism, shallow magmatic intrusions, and transtensional tectonics. Seismostratigraphic analysis of synkinematic strata is constrained by a physical correlation to an already established stratigraphic succession in the neighboring Campi Flegrei and by tephra layers in a gravity core located in Pozzuoli Bay. A stratigraphic resolution in thousands of years was established. Structural and stratigraphic analyses yield quantitative data on the timing of fold inception, kinematics, and the amount and rates of uplift. The folds extend over ∼2 km, and display a curved axial pattern and wedge-shaped packages of synkinematic strata. The rate of fold uplift ranges from 1 to 20 mm/yr. The structures feature limb rotation kinematics and decreasing uplift rates. The uplift rates and geometry of the Pozzuoli Bay folds suggest that they are of tectonic origin and are a product of detachment folding. Their limited longitudinal extent and arcuate axial trends are compatible with an east-trending left transtensional shear zone that was active along the eastern Tyrrhenian Sea during the late Quaternary. A relative sea-level curve was calculated for an anticline culminating in the city of Pozzuoli. This relative sea-level curve highlights the relationship between the deformation timing and the genesis of related abrupt changes in sedimentary facies and erosional surfaces.