Interactions Between Strike-Slip And Thrust Tectonics: Controls on Sand Distributions Through Miocene Basin Arrays, Southern Italy

Butler, Robert W.H.¹, Stefano Mazzoli² (1) University of Leeds, Leeds, United Kingdom (2) University of Naples, Napoli, Italy

The Miocene basins of the Southern Apennines of Italy contain syn-tectonic accumulations of turbidite sands and related deposits. These include thick, reservoir-quality sandstones, some derived from reworked cratonic sediments (e.g. the quartz-arenitic Numidian Flysch) and some from crystalline basement from adjacent mountain belts (e.g. Gorgoglione Flysch). The basins are tectonically controlled, in part by NE-directed thrusting and partly by chiefly left-lateral, NW-SE strike-slip. This case study provides regional and outcrop analogues for other large-scale settings such as the southern Caribbean and parts of SE Asia. The complex kinematic regime of the Southern Apennines reflects the pattern of 3D slab roll-back in the proto Tyrrhenian-Apennine orogen. The resulting evolution of basins is believed to have controlled the routing of major turbidity currents for reservoir sands through time. They also provide otherwise intrabasinal sources for catastrophic calci-metaturbidites within internal basins (e.g. the Cilento Group). While existing studies have treated each Miocene succession as a distinct tectonostratigraphic unit, we use the correlative framework provided by megaturbidites and regionally extensive olistostromal horizons to show stratigraphic links between basins. Modulation of intrabasinal bathymetry is manifest by different distributions of sand net-to-gross between locations. These are interpreted in terms of variations in the degree of flow confinement and flow stripping. The effect is to build distinctive stratigraphies within sub basins. Thus sand quality (relating to the provenance) and sand stacking are intimately related to syn-depositional tectonics, both within the basins and within the orogenic hinterland to control the activity of different clastic source areas.