Structural properties, distribution and internal architecture of synsedimentary submarine mass-transport deposits in southern Italy

A detailed characterization of Mass-Transport Deposits or MTDs, in terms of emplacement processes, depositional products, structural properties and internal architecture, is crucial to define the hydraulic properties of slope-to-basinal deposits. In fact, MTDs are distinct mechanical units and significant heterogeneities within sedimentary succession. They may show different fractures parameters, including intensity and orientation of fractures, when compared to underlying and overlying undeformed strata. MTDs can therefore play a significant role in hydrocarbon exploration and production, inasmuch as they may act as barriers or conduits for fluid flow in the subsurface. The Late Jurassic–Early Cretaceous basinal Maiolica Formation exposed in the Gargano Promontory (southern Italy) represents an ideal natural laboratory to study the stratigraphic architecture of ancient MTDs. This formation consists of undisturbed intervals of flat-lying, light coloured, thin-bedded, cherty micritic limestone interbedded with chaotic intervals characterized by extensively folded and contorted strata of similar facies. The stratigraphic thickness of these deformed strata, which are interpreted to be slump/slide deposits and, to a lesser extent, debris-flow deposits, varies from several decimetres to tens of metres. The internal deformation comprises down-slope verging soft-sediment folds, and both normal and reverse faults. Normal faults are most common in the updip portion of the MTDs, whereas reverse faults are best developed toward their frontal margins, where they often form imbricates of multiple thrusts. In several places, the studied MTDs exhibit signs of reworking, as demonstrated by reactivation of the slump related faults resulting in deformation of beds overlying the MTDs. The structural properties and the distribution of studied MTDs are discussed in the context of the Cretaceous tectonics of the Gargano Promontory, as well as on the characteristics of the paleoslope of the Apulian Platform.