Active foreland deformation evidenced by shallow folds and faults affecting late Quaternary shelf–slope deposits (Adriatic Sea, Italy)

Abstract

ABSTRACTA succession of depositional sequences, recording middle‐late Pleistocene and Holocene glacial–interglacial cycles, documents the impact of short‐term tectonic deformation on the western Adriatic margin. The western Adriatic margin is part of the Apennine foreland which was intensely, though variably, deformed during the Meso‐Cenozoic evolution of the Adriatic region from a passive margin to a foreland basin. The study area extends offshore Gargano Promontory, an uplifted sector of the Adriatic foreland, and includes three major deformation belts located along or cross‐strike to the margin: (1) the NW‐SE Gallignani‐Pelagosa ridge, (2) the WSW‐ENE Tremiti‐Pianosa high (both located north of Gargano) and (3) the W‐E to NW‐SE Gondola fault deformation belt (in the south Adriatic). Long‐term deformation along these tectonic lineaments is documented on conventional low‐frequency seismic profiles by regional folds and faults affecting Eocene–Miocene units overlain by dominantly draping Plio‐Quaternary deposits. At this scale of observation, only north of Gargano Promontory there is some evidence of Plio‐Quaternary units thinning against structural highs, thus suggesting that tectonic deformation was protracted through this interval. Based on new high‐resolution seismic data, we show that deformation along these pre‐existing tectonic structures continued during the Quaternary, affecting middle‐late Pleistocene and even Holocene units on the shelf and upper slope north and south of Gargano Promontory. These recent deformations consist of gentle folds and high‐angle faults, locally producing topographic relief that affects the stratigraphy and thickness of syn‐tectonic deposits. We interpret the small‐scale, shallow faults and gentle folds affecting middle‐late Pleistocene and Holocene deposits, north and south Gargano Promontory, as the evidence of ongoing foreland deformation along inherited regional fold and fault systems.