Tectonic and climatic forcing on shelf margin slope progradation in the Adriatic Sea: inferences from seismic and well data and 3D numerical forward modelling

The architecture of sedimentary basins is shaped by the interplay between relative sea-level changes and sediment supply combined with sediment transport processes. Relative sea-level changes are controlled by both eustatic sea-level variations and tectonics. While the effects of these factors on stratal stacking patterns have been a focus of extensive research, their distinct contributions remain incompletely understood.

In this study, we interpreted high-resolution seismic profiles together with deep well data from the South Adriatic Foredeep (SAF), focusing on tectonic and sedimentary processes and sea-level fluctuations over the last 5.3 Ma. The SAF is an active basin, bounded by the Dinaric/Albanian thrust front and Apennine thrust/Apulian platform. Furthermore, the sedimentary system was further analysed by the means of 3D stratigraphic numerical modelling with DionisosFlow that accounts for the variability of the sediment and water flux combined with climatic and sea level variations, and sediment compaction. A series of models were conducted testing different subsidence, sediment supply and water discharge values, eustatic curves and sediment compaction parameters on the overall basin morphology.

Based on the joint interpretation of the observational and model data, we propose a new stratigraphic model for the Miocene to Recent sedimentary evolution of the South Adriatic Foredeep. The basin is characterized by the variable length of the shelf around the basin margin with deposits of the deep-water gravity flow and bottom-currents on the slopes. The progradation of the shelf in NW reached up to 55 km, on top of the Apulian platform around 50 km, while at the footwall of the Dinaric thrust belt varies from 15 km to 30 km, with different thicknesses. The rate of the progradation at some places increased three times during Pleistocene, e.g. from 5,5 to 16 m/kry. Calculated subsidence also varies around the basin affecting the lateral change in accommodation space. Finally, the sedimentary architecture on the shelf is overprinted by compaction effects, which are most pronounced over basin confinements, sometimes causing significant deformation and subsequent aggradation.

A key characteristic is the pronounced variability in sediment deposition along basin margins, driven by local tectonic and climatic forcing, as well as variation in autogenic processes. We conclude that the overall progradation was shaped by variable long-term (> 100 kyr) versus short-term (<100 kry) forcing factors. In the long run, i.e. from the beginning of the Pleistocene, repeated glaciations led to greater water fluxes and sediment supply, resulting in higher progradation rates. The tectonic influence on the rates of accommodation space do not show abrupt changes over time. Short-term factors influencing the water flow and sediment discharge in combination with the fall and rise of sea level lead to high-frequency changes in stratigraphy and are responsible for the formation of clinoforms on the basin slopes.

Beicip-Franlab is acknowledged for providing an academic license for DionisosFlow. This study was supported by the Croatian Science Foundation as part of the Outgoing Mobility Program.