Deep gullies entrenchment in valley fills during the Late Holocene in the Basento basin, Basilicata (southern Italy) [Creusement de profondes ravines à l’Holocène supérieur dans les remblaiements fluviatiles du bassin de Basento, Basilicata (Italie du sud)]

Deeply entrenched channels namely badland gullies occur on the gently sloping valley floors of any alluvial basins in the semi-arid environments of Fossa Bradanica, Basilicata, southern Italy. Valley fills in this region consist of predominantly Holocene alluvium; late Pleistocene deposits occur as terraces above the present flood plain or as eroded benches buried beneath younger alluvium. Historical fluvial deposition began before 7000 a cal. BP and ended at around 120 a cal. BP. In this study, we focus on the channel entrenchment (badland gullies incision) in the last 4500 years, based on a detailed study of chronostratigraphic alluvial sequences of Basento River. Four main phases of incision have been recorded at around 4500-4350, 1500, 900-800, and 120 a cal. BP. The formation of late-Holocene badland gullies can be related to changes in climate, vegetation and groundwater conditions. Environmental history mainly derived from the high-resolution pollen record of Lago Grande di Monticchio. Badland gullies formation appears to be linked to repeated dry-wet cycles. During dry periods, water tables significantly dropped and vegetation cover decreased with increase in runoff and water discharge from rainfall, leading to deepening and widening of stream channels.Des profondes ravines se sont développées sur les versants légèrement pentus situés en marge des plaines alluviales de différents bassins hydrographiques de Lucanie, dans le sud de l’Italie. Dans cette région, les remblaiements de vallée sont principalement holocènes; des dépôts datant du Pléistocène supérieur, mal conservés, affleurent au niveau de terrasses situées le long de tous les principaux cours d’eau. La phase de dépôt holocène débute à partir de 7000 cal. BP et se termine vers 120 cal. BP. L’étude focalise sur l’incision des ravines durant les derniers 4500 ans ; elle s’appuie sur l’analyse chronostratigraphique détaillée des dépôts alluviaux du fleuve Basento. Quatre principales phases d’incision sont mises en évidence : 4500-4350, 1500, 900-800 et 120 cal. BP. La mise en place des ravines durant l’Holocène supérieur est en lien avec les changements du climat, de la végétation et des conditions des eaux souterraines. L’histoire environnementale dérive principalement des séquences polliniques du Lago Grande de Monticchio, où la mise en place du ravinement semble associée à des cycles sécheresse/humidité répétés. Quand le climat devient plus sec, la diminution du couvert végétal et l’augmentation du ruissellement le long des versants entraînent un approfondissement et un élargissement des ravines

Some considerations on the application of the classical strength criteria for carbonate rock masses: a case study in a quarry in Apulia (Italy)

In questo lavoro viene presentato un esempio di applicazione dei “classici” criteri di rottura degli ammassi rocciosi su un fronte di cava per la produzione di inerti da roccia calcarea (cava “di Maso”, Bari). La successione ivi affiorante è costituita da calcari mesozoici su cui giace in trasgressione una sottile copertura di calcarenite pleistocenica. La roccia calcarea, intensamente fratturata e carsificata, è stata classificata dal punto di vista geomeccanico, con i sistemi RQD, Q, RMR, RMi, SMR e GSI. Le classificazioni utilizzate hanno indicato che l’ammasso roccioso calcareo è di qualità scadente o molto scadente, ad eccezione dell’RMi e del GSI per le quali lo stesso risulta, rispettivamente, buono e discreto. Successivamente, per la valutazione della resistenza di picco sono stati applicati e confrontati i criteri di Mohr-Coulomb e di Hoek-Brown, mentre per la resistenza residua quelli di Patton, di Barton e di Zhao

Petrographic features influencing basic geotechnical parameters of carbonate soft rocks from Apulia (southern Italy)

A multidisciplinary petrographic and geotechnical approach, aimed at understanding the conditioning by rock-fabric on the mechanical properties of carbonate soft rocks, is shown in this paper. The analysed rocks extensively crop out in the Apulia region and can be referred to three geological units: Pietra leccese (Late Burdigalian-Early Messinian), Calcarenite di Gravina (Middle Pliocene-Early Pleistocene) and Salentino Supersynthem (Midde-Late Pleistocene). 69 specimens of carbonate soft rocks, belonging to all these units, were selected from different sectors of Apulia region and characterized according to petrographic, physical and mechanical properties. Petrographic data allowed us to group all specimens in the following six classes: i) wackestone; ii) mud-dominated packstone; iii) packstone; iv) grainstone; v) floatstone; vi) rudstone. Differently, uniaxial compression strength (UCS) values classify the most part of specimens in â\u80\u9cvery low and low strengthâ\u80\u9d, revealing a dominant weak resistance and high deformability. Particular attention has been given to the relationships between petrographic features and physical and mechanical parameters of the Apulian soft rocks by means of statistical tests based on the univariate analysis of variance (one-way Anova) and on the principal component analysis (PCA). At first, statistical analysis revealed that the rock geotechnical values are strictly dependent from the geological units. Particularly, the samples of Pietra leccese show significantly higher means of UCS, Young's modulus (Et), and dry unit weight than samples of the Calcarenite di Gravina Fm. Conversely, samples of this latter unit have significantly higher means of porosity, imbibition coefficient and permeability coefficient than those ones of the Pietra leccese fm. Moreover, statistical analysis was applied to estimate if geotechnical values differ according to the petrographic classes of the Calcarenite di Gravina Fm and to verify the covariance between the geotechnical parameters of this unit. The following results have been remarked: i) floatstone and rudstone have significantly higher means of UCS and dry unit weight, and lower means of porosity than finer-grained classes; ii) mud-dominated packstone has significantly lower means of UCS, dry unit weight, Et and permeability coefficient and higher means of porosity and imbibition coefficient than other petrographic classes; iii) grain-dominated, matrix-free, rudstone and grainstone have significantly higher values of permeability coefficient than mud-dominated classes; iv) the occurrence of carbonate lithoclasts and of different dominant couples of sparry cement in pore spaces, are two of the most important controlling factors of the rock strength, and can also explains much of the intraformational variability observed in geotechnical data. Total porosity has not a clear correlation with permeability. This means that the contribution of isolated pore spaces to the total porosity is relevant in Apulian soft rocks, as also suggested by the relatively low values of permeability compared to the relatively high percentages of total porosity. A multidisciplinary characterization of carbonate soft rocks based on petrographic analysis and geotechnical determination of physical and mechanical properties is here recommended for future studies since this approach can give useful information to understand the peculiar behaviour of carbonate soft rocks and to drive the subsequent geotechnical investigations

Reply to ‘Comment on “Petrographic features influencing basic geotechnical parameters of carbonate soft rocks from Apulia (southern Italy)” [Eng. Geol. 233: 76–97]’

Aiming 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