1,720,983 research outputs found
Integrated Geological and Digital Surveys to Know, Preserve and Promote a Geoheritage: the Sea Cliff of Vignanotica Bay (Gargano Promontory, Southern Italy)
No full textThe sea cliff of Vignanotica Bay (Gargano Promontory, Southern Italy) is a site that, for its peculiar geological features, can be considered a witness of geodiversity and that, as such, should be evaluated as geosite. Since it is necessary to first know, then enhance, and finally protect a geosite, here we propose a modern method of study aimed at the understanding and dissemination of geological knowledge to a wide audience of non-experts. The cliff, located in the Gargano National Park, was investigated using both stratigraphic-sedimentological and digital methods. The former method, realised using macrofacies and microfacies analysis, allowed us to study features of a deep-marine environment, characterised by subaqueous slides (slumpings). The latter method allowed us to achieve a virtual 3D model of the entire sea cliff, highlighting many geological features, often difficult to observe since they are exposed along high vertical walls. The combined use of these methods led to a complete characterisation of the cliff, useful both to promote geological knowledge and to preserve the site
Hierarchies of stratigraphic discontinuity surfaces in siliciclastic, carbonate and mixed siliciclastic‐bioclastic tidalites: Implications for fluid migration in reservoir quality assessment
No full textThe hierarchies of the stratigraphic discontinuity surfaces observed in ancient tidalites are qualitatively assessed, aiming to evaluate their role as possible preferential conduits for fluid migration. Three outcrop examples are presented from microtidal settings of southern Italy: (i) siliciclastic tidalites consisting of quartz-rich cross-stratified sandstones generated by strong two-directional tidal currents flowing along a tidal strait; (ii) carbonate tidalites, which accumulated in a Cretaceous lagoon and tidal flat where peritidal cycles formed vertically-stacked sequences of biopeloidal and fenestral packstones, wackestones and bindstones during repeated phases of Milankovitch-scale sea-level changes; (iii) mixed, siliciclastic-bioclastic tidalites, deposited in a bay and recording offshore-transition, to shoreface wave-dominated and tide-influenced environments. Observations made during this study suggest that fluid movement can be controlled by the presence of main bounding surfaces that occur at different dimensions, from large (hectometre)-scale, to medium (decametre)-scale, to smaller (metre)-scales. These surfaces produced either by depositional or erosional processes, are characterised by different features and geometries in siliciclastic, carbonate and mixed siliciclastic-bioclastic tidalites arguably revealing complex internal pathways for fluid flows. These results suggest that fluids propagating along the main discontinuities follow a dominant sub-horizontal direction of propagation, associated with minor sub-vertical movements, due to local internal surface geometries and interconnections and a general lack of fractures. This surface-based approach to the study of fluid-flow transmission within stratified rocks represents a conceptual attempt to predict fluid mobility and reservoir potential in tidalite-bearing siliciclastic, carbonate and mixed reservoir rocks.The hierarchies of the stratigraphic discontinuity surfaces observed in ancient tidalites are qualitatively assessed, aiming to evaluate their role as possible preferential conduits for fluid migration. Three outcrop examples are presented from microtidal settings of southern Italy: (i) siliciclastic tidalites accumulated in a strait; (ii) carbonate tidalites, accumulated in a lagoon and tidal flat; and (iii) mixed siliciclastic-bioclastic tidalites deposited in a bay.imag
Cretaceous cyclic peritidal carbonates of the Apulia Carbonate Platform (Apulia, southern Italy) in a hierarchical sequence‐stratigraphic perspective: A case study from the Murge area (the Giovinazzo sea‐cliff section)
Full text linkCretaceous cyclic peritidal carbonates form the bulk of the Apulia Region in Italy and represent the vestiges of the Apulia Carbonate Platform. To show from a sequence stratigraphic perspective the architecture of peritidal carbonates, the 17 m thick Albian Giovinazzo sea-cliff section was studied at a centimetre detail, aiming to: (i) describe cyclic facies organisation in beds and bedsets; (ii) reconstruct the relative sea-level curve and its evolution over time; (iii) interpret the long-term evolution of the accommodation space in terms of sequence stratigraphy. The hierarchical stacking pattern of facies in beds and bedsets reveals Milankovitch cyclicity. As a working hypothesis, elementary sequences are assumed to represent the precession cycle (ca 20 kyr) and small-scale and medium-scale sequences the short (ca 100 kyr) and long (ca 400 kyr) eccentricity cycles, respectively. Four different types of elementary sequences (condensed, catch-down, catch-up and give-up) are recognised and interpreted in terms of relative sea-level changes to reconstruct the relative sea-level curve of the entire succession. The envelope of the reconstructed relative sea-level curve is used to represent the long-term accommodation change on the platform, which covers a time span of approximately 1.8 Myr. Most of this time was spent in subaerial exposure, as approximately 1.2 Myr was predicted to be condensed in a stratigraphic interval encompassing both the sequence-boundary zone/falling stage deposits and the lowstand deposits. Moreover, it was interpreted that about two-third of the total thickness of the succession was formed in only 280 kyr and consisted of both transgressive and maximum-flooding deposits. The main implication of this study is that unconformities do not necessarily correspond to single surfaces but, rather, to very amalgamated intervals or unconformity zones. Moreover, based on biostratigraphic constraints, there is a correlation between the unconformity zone of the studied succession and the third-order KAl4 sequence boundary of the Cretaceous eustatic cycle chart.Four different types of elementary sequences (condensed, catch-down, catch-up and give-up) were recognised and interpreted in terms of relative sea-level changes to reconstruct the relative sea-level curve of the entire succession. The envelope of the reconstructed relative sea-level curve was used to represent the long-term accommodation change on the platform, that covers a time span of approximately 1.8 Myr. Most of this time was spent in subaerial exposure, as approximately 1.2 Myr was predicted to be condensed in a stratigraphic interval encompassing both the sequence boundary zone/falling stage deposits and the lowstand deposits. Moreover, it was interpreted that about two-third of the total thickness of the studied succession was formed in only 280 kyr and consisted of both transgressive and maximum flooding deposits.imag
The role of pedogenic calcrete in deciphering the record of relative sea-level changes and climate conditions in mid-Cretaceous peritidal limestones of the Apulia Carbonate Platform (Italy)
No full textDepositi carbonatici infrapleistocenici di tipo foramol in sistemi di scarpata (Salento – Italia meridionale)
Full text linkAlong the eastern Salento coast (Southern Italy), Cretaceous to Quaternary carbonates crop out on a 100 m high escarpment that connects a wide and relatively flat area to the Otranto Strait (Ionian Sea). Along the escarpment, faulted and tilted Cretaceous and Eocene limestones record deposition in shallow-marine and marginal carbonate environments. Younger carbonates disconformably overlie this substratum and they formed when the region was partially submerged. Accordingly, Priabonian to Messinian carbonates which crop out along the escarpment were interpreted as slope deposits linked to reef systems developed on the margin of the top area, while lower Pleistocene carbonates cropping out at the base of the same escarpment were considered coastal in origin and formed during the uplift of the region. Stratigraphic and sedimentologic studies carried out on these lower Pleistocene carbonates demonstrate that also these deposits should be considered as slope deposits. The studied carbonates are foramol-type ones and discontinuously crop out along the lower part of the escarpment. They show a variable thickness (from a few meters up to several tens) and often exhibit a fan morphology; they correspond to small isolated bodies (up to a few km2 wide) developed in some indentations of the escarpment, and are composed of coarse skeletal grains mainly deposited via slumpings or grain flows. Successions are characterized by long clinobeds cut by slump scars downward passing to gullies; backsets, slumps and chaotic deposits fill these erosional features. Clinobeds are alternatively made up of molechfor and rodhalgal facies which respectively record resedimentation by grain flows of shallow marine carbonates developed on top of the region and along-slope carbonate production. Depositional systems correspond to small shallow-marine aprons whose discontinuous distribution along the escarpment (inside indentations) should be considered an original feature. The idea that these deposits record the Sicilian sea-level along the escarpment should be abandoned as they are not coastal deposits. The studied deposits should be correlated to the Calcarenite di Gravina Formation which in other areas of the Apulian Foreland (which the Salento region belongs to) are considered as the deposits linked to the subsidence induced by the estward migration of the south- Apennines orogenic system. The Quaternary uplift of the Salento region should be begun after the deposition of the studied slope deposits, as indicated also by a series of middle-upper Pleistocene marine terraces which start at heights higher than those ones of the studied deposits
3D modelling of the Tremiti salt diapir in the Gargano offshore (Adriatic Sea, southern Italy): constraints in the Tremiti Structure development
No full textThe reinterpretation of public seismic profiles, the stratigraphic review of hydrocarbon exploration well logs in the Adriatic offshore of Gargano (Apulia, southern Italy), and the use of Surfer® (Golden Software, Inc.) and MoveTM (Midland Valley Ltd.) softwares, allowed us to obtain the Two Way Times (TWT) contour map and the 3D model of the upper Trias salt surface of the Tremiti diapir.
The obtained 3D model of the Tremiti diapir shows two types of shape indicating at least as many modes of salt emplacement: single flap and piercing. Inherited faults were used by salt, which promoted the contemporaneous development of piercing and single flap in the same diapiric body.
In addition, the sea floor deformations suggest that the diapirism, which mostly developed during Plio-Pleistocene time, is probably still active. Despite the NW-SE shortening due to the regional EW dextral shearing, that likely triggered halokinesis, the upward growth rate of the diapir was able to promote dip-slip kinematics, which locally hid the strike-slip one
The Tremiti Salt Structure in the Adriatic Sea (Gargano offshore, Apulia, southern Italy)
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Reply to ‘Comment on “Petrographic features influencing basic geotechnical parameters of carbonate soft rocks from Apulia (southern Italy)” [Eng. Geol. 233: 76–97]’
No full textAiming to investigate the implications of the rock-fabric on some basic geotechnical parameters, the paper by Festa, Fiore, Luisi, Miccoli, and Spalluto (2018) mostly focused on the compositional, textural, and diagenetic aspects of the carbonate soft rocks from Apulia (southern Italy). So, further geotechnical considerations are always welcome for a more comprehensive discussion about the soft rocks' mechanical behavior of concern.
With this perspective, the comment by G.F. Andriani (Andriani, 2021) to the paper by Festa et al. (2018) includes some geotechnical considerations and new data (albeit from a couple of samples) for the general discussion on the mechanical behavior of soft rocks from Apulia, although representing neither comments nor criticisms. In this comment, for some criticisms, the reply can be easily found in Festa et al. (2018); for other criticisms, they give us a chance to clarify some topics that were not discussed in depth before.
According to the comment by Andriani (2021), the main criticisms that need replies include (i) improbable degree of saturation exceeding 100%, (ii) unlikely closed porosity, (iii) weakness of the dataset and scarcity of data, and (iv) insignificance of the uniaxial compressive strength vs. both imbibition and permeability coefficients. Therefore, the replies to these criticisms are assessed in the following sections: 2. the comment regarding degree of saturation; 3. the comment regarding porosity; 4. the comment regarding dataset; and 5. the comment regarding uniaxial compressive strength (UCS) vs. Imbibition and Permeability Coefficients. Finally, the replies to Andriani (2021) criticism regarding the lack of accurate comparative analysis have been disputed in 3 The comment regarding porosity, 4 The comment regarding dataset
New insights on diapirism in the Adriatic Sea: the Tremiti salt structure (Apulia offshore, southeastern Italy)
No full textThe reinterpretation of public seismic profiles in the Adriatic offshore of Gargano (Apulia, southern Italy) allowed the detection of a kilometre-scale salt-anticline, the Tremiti diapir, within the larger Tremiti Structure. This anticline was generated by diapirism of Upper Triassic anhydrites within a thick Mesozoic to Quaternary basinal sedimentary succession. Both internal stratal patterns and shapes of Plio-Quaternary units, and the occurrence of an angular unconformity between early Tortonian and Pliocene rocks on the Tremiti Islands, suggest that halokinesis began during the late Miocene and is still active today. An ancient extensional SE dipping fault, cutting an older Mesozoic low-amplitude anhydritic ridge, played an important role during salt mobilization, which was promoted by NW-SE shortening. The diapir grew in the footwall of this fault, causing its upward propagation. In some places, the ancient fault served as a preferential channel for the upward migration of the anhydrites
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