The assessment of deformation types within the slope of a carbonate platform can be complicated by the\ud possible interaction of rooted (tectonically-induced) and superficial (gravity-driven) structures. An ideal\ud case study to document and distinguish tectonically- and gravity-driven structures is provided by the\ud Cretaceous slope-to-basin carbonates exposed in the Gargano Promontory, southern Italy. These carbonates\ud formed adjacent to the Apulian platform margin, which was oriented approximately NEeSW to\ud NWeSE along the southern and northern edges of the promontory, respectively. Slump-related folds are\ud characterised by axial planes typically oriented either sub-parallel or at small angles to the strike of the\ud inferred paleoslope. In fact, the strike of folds is roughly NEeSW in the southern portion of the study\ud area, whereas it is NWeSE in the northern part. Correspondingly, gravity-driven normal and reverse\ud faults strike sub-parallel and at acute angles to the adjacent Apulian paleoslope. Cretaceous tectonic\ud faults in the slope-to-basin carbonates form two principal sets striking NWeSE and WNW-ESE. The\ud former set is made up of normal faults and the latter one includes mainly oblique-slip normal faults.\ud Neither normal nor oblique-slip normal faults show any relationship with the geometry of the paleoslope.\ud The results obtained from this study may help the interpretation of subsurface data in those\ud geological contexts in which the interplay of gravitational and tectonic processes is responsible for\ud deformation
Bedding-parallel stylolites typically represent the product of chemical compaction (overburden weight-induced pressure solution) experienced by carbonate successions during their burial history, when bedding is still horizontal. Due to their common occurrence in carbonate rocks, with lateral extents that can exceed 1 km, beddingparallel stylolites are of special interest for the hydrocarbon industry because they may affect the regional fluid flow in the subsurface. Aimed at assessing the development and distribution of beddingparallel stylolites in shallow-water, platform limestone successions, field and laboratory studies were carried out on Cretaceous limestones originally pertaining to the Apulian Carbonate Platform realm and now exposed in three distinct Italian locations: Maiella Mountain, Gargano Promontory and Murge Plateau.Results point to a prominent role played by the geological characteristics of limestones on development and localization of beddingparallel stylolites within shallow-water, platform limestone successions. In particular, bedding-parallel lamination and fine rock grain size, co-occurring in stromatolitic limestones, determined there laterally more extensive and closely spaced stylolites than in the associated calcilutites and calcarenites. Large fenestral pores, which are ubiquitous in stromatolitic limestones, represent rock heterogeneities able to influence the roughness of individual stylolites.Laboratory measurements revealed that the permeability of the studied Cretaceous limestones is very low (<10 µD). Pilot tests suggest that bedding-parallel stylolites in stromatolitic layers are not barrier to fluid flow but may represent pathways through low-permeability, platform limestone successions in the subsurface.
A detailed characterisation of submarine mass-transport deposits (MTDs), in terms of both emplacement processes and internal architecture of depositional products, is crucial to define the hydraulic properties of slope-to-basinal deposits. The Late Jurassic-Early Cretaceous basinal Maiolica Formation exposed in the Gargano Promontory (southern Italy) represents an ideal natural laboratory to study the complex stratigraphic architecture of ancient MTDs. This formation consists of undisturbed intervals of flat-lying, thin-bedded, cherty micritic limestone interbedded with intervals of lithologically similar, but chaotic strata that are characterized by significant internal distortion. The stratigraphic thickness of these deformed units, which are interpreted to represent several types of mass movements (e.g., slumps and, to a lesser extent, slides and debris flows), varies from several decimetres to tens of metres.\ud The internal deformation features comprise down-slope verging folds, together with both normal and reverse faults. In several places, the studied MTDs exhibit signs of reworking, as demonstrated by reactivation of the slump-related faults resulting in deformation of beds directly overlying the MTDs. Structural features within MTD’s, provide information about the direction of the mass movement, and hence the orientation of the paleoslope. Measurements in the eastern and north-eastern part of Gargano Promontory suggest flow is directed towards the E and N respectively. The internal architecture of studied MTDs is discussed in the context of triggering mechanisms related to the characteristics of the Cretaceous paleoslope of the Apulian Platform
Fault-controlled dolostone bodies have been described as potential hydrocarbonbearing reservoirs. Numerous case studies have described the shape and size of these often non fabric selective dolostone bodies within the vicinity of crustal-scale lineaments, usually from Palaeozoic or Mesozoic carbonate platforms, which have undergone one or more phases of burial and exhumation. There has been little attention paid, however, to fault-strike variability in dolostone distribution or the preferential localization of these bodies on particular faults. This study focuses on dolostone bodies adjacent to the Hammam Faraun Fault (HFF), Gulf of Suez. This crustalscale normal fault was activated in the Late Oligocene, coincident with the onset of extension within the Suez Rift. Dolomitization in the prerift Eocene Thebes Formation occurred in the immediate footwall of the HFF forming two massive, non facies selective dolostone bodies, ca. 500 m wide. Facies-controlled tongues of dolostone on the margins of the massive dolostone bodies extend for up to 100 m. The geochemical signature of the dolostone bodies is consistent with replacement by Miocene seawater, contemporaneous with the rift climax and localization of strain along the HFF. A conceptual model of dolomitization from seawater that circulated within the HFF during the rift climax is presented. Seawater was either directly drawn down the HFF or circulated from the hanging wall basin via a permeable aquifer towards the HFF. The lateral extent of the massive dolostone bodies was controlled by pre-existing HFF-parallel fracture corridors on the outer margins of the damage zone of the fault. The behaviour of these fracture corridors alternated between acting as barriers to fluid flow before rupture and acting as flow conduits during or after rupture. Multiple phases of dolomitization and recrystallization during the ca.10 Ma period in which dolomitization occurred led to mottled petrographical textures and wide-ranging isotopic signatures. The localization of dolomitization on the HFF is interpreted to reflect its proximity to a rift accommodation zone which facilitated vertical fluid flow due to perturbed and enhanced stresses during fault interaction. It is possible that the presence of jogs along the strike of the fault further focused fluid flux. As such, it is suggested that the massive dolostones described in --
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