Soft-sediment deformation induced by sinkhole activity in shallow marine environments: A fossil example in the Apulian Foreland (Southern Italy)

Soft-sediment deformation structures are exposed in sea cliffs in the lower part of the Calcarenite di Gravina Formation (late Pliocene-early Pleistocene) in the Cala Corvino area N of Monopoli (Adriatic sector of the Apulian Foreland, southern Italy). Deformation affects a thickness of about 5 m involving a lower calcareous-terrigenous sand and gravel unit and an upper heavily bioturbated grainstone and packstone unit. Deformation is absent from the overlying part of the succession. Large-scale soft-sediment deformation structures are collapse features comprising irregularly elongated conical zones of sinking. In vertical section, narrow "drop" zones occur in the lower sandy-gravelly facies and large gentle folds in the upper grainstone-packstone beds. The degree of deformation decreases upwards. Small-scale soft-sediment deformation structures adjacent to the large-scale conical collapse structures are narrow, vertically elongated load structures about 2 m high and 30-50 cm wide that involve only the basal terrigenous facies. The distribution of small- and large-scale soft-sediment deformation structures corresponds closely to zones of fracturing in the underlying Cretaceous limestones, and the elongation directions of soft-sediment deformation structures correspond to the orientation of major fractures in the limestones. The soft-sediment deformation occurred due to collapse associated with karstic sinkhole formation along fractures in the bedrock Geometrical relationships between deformed and undeformed sedimentary units show that deformation occurred in a shallow marine environment. The structures at Cala Corvino provide a rare outcrop-scale record of sinkhole-induced soft-sediment deformation occurring in a shallow marine environment.