Internal architecture of mass-transport deposits in basinal carbonates: A case study from southern Italy

Submarine mass-transport deposits represent important stratigraphic hetero-geneities within slope and basinal sedimentary successions. A poor under-standing of how their distribution and internal architecture affect the fluidflow migration pathway may lead to unexpected compartmentalizationissues in reservoir analysis. Studies of modern carbonate mass-transportdeposits mainly focus on large seismic-scale slope failures; however, thenear-platform basinal depositional environment often hosts mass-transportdeposits of various dimensions. The small-scale and meso-scale (metres toseveral tens of metres) carbonate mass-transport deposits play a considerablerole in distribution of sediment and therefore have an impact on the hetero-geneity of the succession. In order to further constrain the geometry andinternal architecture of mass-transport deposits developed in near-slope basi-nal carbonates, a structural and sedimentological analysis of sub-seismic-scale mass-transport deposits has been undertaken on the eastern margin ofthe Apulian carbonate platform in the Gargano Promontory, south-east Italy.These mass-transport deposits, that locally comprise a large proportion (50to 60%) of the base of slope to basinal sediments of the Cretaceous MaiolicaFormation, typically display a vertically bipartite character, including deb-rites and slump deposits of varying volume ratios. A range of brittle andductile deformation styles developed within distinct bed packages, togetherwith the presence of both chert clasts, folded chert layers and spherical chertnodules, suggest that sediments were at different stages of lithification priorto downslope movement associated with mass-transport deposits. This studyhelps elucidate the emplacement processes, frequency and character of sub-seismic-scale mass-transport deposits within the basinal carbonate environ-ment, and thereby reduces the uncertainties in the characterization ofsubsurface carbonate geofluid reservoirs.