Bollettino Della Societa Geologica Italiana最新文献

{"title":"The Carboniferous-mid Permian successions of the Northern Apennines: new data from the Pisani Mts. inlier (Tuscany, Italy)","authors":"F. Marini, E. Pandeli, M. Tongiorgi, E. Pecchioni, L. Orti","doi":"10.3301/ijg.2019.27","DOIUrl":"https://doi.org/10.3301/ijg.2019.27","url":null,"abstract":"This paper updates and partially modifies the knowledge of the geological-palaeoenvironmental and geodynamic framework of the Tuscan segment of the Variscan Chain in Tuscany during Permian times. Particularly, it adds new data on the contact between the upper Carboniferous-lower Permian San Lorenzo schist (SLs) and the mid-Permian Asciano breccia and conglomerate (Abc) clastic formations in the Pisani Mts. metamorphic inlier which represents one of the pinning point outcrops for the study of the upper Paleozoic sequences in the Northern Apennines. Their sharp unconformable contact is well-documented in the literature at map and outcrop scale and was ascribed to the Saalian phase of the Variscan orogeny that would have occurred in correspondence of a climatic change from equatorial to an semi-arid tropical conditions. New geological investigations on the SLs and Abc allowed us to identify the finding of a continuous stratigraphic section in the Pian della Conserva locality (northwestern Pisani Mts.) where the organic matter-rich SLs conformably passes upwards to the reddish immature, mainly coarse-grained deposits of Abc through a decametric transition zone. The section was studied in detail from a lithological-sedimentological point of view and sampled for petrographic, mineralogic and chemical studies. The data show that the passage from SLs to Abc testifies a main change from an equatorial, wet fluvial-lacustrine environment to a well-drained, alluvial fan systems in a monsoon- like climate. This event can be related to the reactivation of the previous late Carboniferous-lower Permian shear zones during the mid-Permian times that produced morpho-tectonic highs subjected to a rapid erosion and the formation of unconformities, whereas the presence of a few residual fluvial plain areas, characterized by dysoxic conditions, is documented by the gradual passage between SLs and Abc in the Pian della Conserva section. In addition, the presence of a metavolcanoclastic or metaepiclastic layer was also recognized in the uppermost part of the SLs and it represents the first evidence of a late Carboniferous-early Permian volcanic event in the Northern Apennines.","PeriodicalId":55341,"journal":{"name":"Bollettino Della Societa Geologica Italiana","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2020-06-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"80445163","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Anatomy and Jurassic evolution of a Hercynian basement high (Caloveto High - Calabria, Southern Italy)","authors":"M. Santantonio, S. Fabbi","doi":"10.3301/IJG.2019.16","DOIUrl":"https://doi.org/10.3301/IJG.2019.16","url":null,"abstract":"The Caloveto area in North-East Calabria hosts a stratigraphic succession which documents the evolution from shallow water carbonates to deeper-water pelagic and hemipelagic deposits, bearing ample evidence for severe tectonic control on Jurassic and Lower Cretaceous sedimentation. Geological mapping indicates that the shallow-water carbonates, also with coral assemblages, formed a narrow fringe around a high of the Hercynian basement, made of lowgrade metamorphic rock, which remained emergent throughout the Pliensbachian and became an intrabasinal high which stood proud of the Longobucco basin, hosting thin pelagic sedimentation through most of the Jurassic. An extensional phase in the Toarcian disrupted and foundered the benthic carbonate factory, whose drowning isdocumented by a change to Rosso Ammonitico-type deposits. This resulted in a complex network of neptunian dykes (also intruding the basement) and in-situ breccias. Starting in the late Toarcian, the rugged submarine topography was gradually leveled by onlapping marls, radiolarites and pelagic limestone, which sealed the Toarcian fault zones producing a diverse array of unconformities. Colonization by microbial communities characterizes the initial stages ofmarine sedimentation around the cores of Paleozoic basement, as banded polychrome microbialites and “swollen” phyllites, a result of the microbially-influenced/induced displacive growth of calcium carbonate crystals along split cleavage planes, constitute an unexpected field tool for identifying basin margins. Silicified marginal zones in the shallow water limestone characterize, in analogy withother Tethyan regions, the onlap unconformities of chert-rich basinal units on the submerged carbonate fringes.","PeriodicalId":55341,"journal":{"name":"Bollettino Della Societa Geologica Italiana","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2020-02-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"90483804","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Drowning of microbial mounds on the slopes of the Latemar platform (middle Triassic)","authors":"M. Franceschi, N. Preto, M. Caggiati, Giovanni Gattolin, A. Riva, P. Gianolla","doi":"10.3301/ijg.2019.23","DOIUrl":"https://doi.org/10.3301/ijg.2019.23","url":null,"abstract":"Two microbial mound-shaped carbonate bodies buried below the slope deposits of the middle Triassic Latemar platform (Dolomites, Italy) have been studied. The two sedimentary bodies, after having reached different stages of evolution, drowned and were covered by the slopes of the Latemar carbonate platform. The estimation of the depth and time at which they were located when they were buried made it possible to infer the average rates of relative sea-level rise to which they were subjected, revealing that these latter exceeded the growth rate of the main Latemar buildup. Given the estimated rates of sea-level rise, the two satellite bodies reached a critical depth at which microbial carbonate production stops, or it is significantly reduced, before being buried. As extensional tectonics was active in the area of the Dolomites during the Anisian, subsidence is the more likely cause of sea level rise. It is therefore hypothesized that the cause of the ultimate drowning of the “mounds” were subsidence rates exceeding their aggradation potential and inducing a progressive deepening that brought them below the lower depth threshold of microbial carbonate production.","PeriodicalId":55341,"journal":{"name":"Bollettino Della Societa Geologica Italiana","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2020-02-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"78437210","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Non-condensed shell beds in hiatal successions: instantaneous cementation associated with nutrient-rich bottom currents and high bivalve production","authors":"A. Tomašovỳch, J. Schlögl, J. Michalík, Lenka Donovalová","doi":"10.3301/ijg.2019.21","DOIUrl":"https://doi.org/10.3301/ijg.2019.21","url":null,"abstract":"Pelagic carbonate deposits formed by the thin-shelled, epifaunal, originally bimineralic bivalve Bositra buchi were geographically widely distributed in the Tethyan basins during the Middle Jurassic. Here, to evaluate conditions that allowed the formation of peculiar, metre-scale, densely-packed shell beds primarily formed by Bositra, we assess size distributions and preservation of this bivalve in thin sections at ten sites in the Pieniny Klippen Belt and Peri-Klippen units (Western Carpathians), representing a bathymetric transect from pelagic-platform tops with shell beds up to slope environments where small filaments occur with spicules and radiolarians. Although Bositra shell beds are modulated by transport and winnowing, three types of evidence indicate that they primarily reflect high bivalve productivity. First, we find that size distributions of this species form a bathymetric gradient, from the dominance of remains smaller than 0.5 mm in low- energy slope environments, to 0.5-2 mm on muddy platform edges, up to lensoid shell beds with large valves (~2-15 mm) occurring on platform tops exposed to bottom currents. Although sediment winnowing from shell beds contributed to the rarity of small-sized specimens in platform-top environments, the bathymetric shift in the shape of size distributions is not purely driven by fragmentation and by size-selective transport of small specimens into slope environments because the average valve thickness declines with depth and thick fragments do not occur in slope environments. High abundances of suspension-feeding Bositra preferentially associated with indicators of bottom currents at oligophotic or aphotic depths indicate that plankton productivity was probably sourced by nutrient-rich internal waves that intersected platform tops, leading to low juvenile mortality in Bositra populations. In contrast, populations in deeper environments with the limited input of particulate organic matter failed to achieve maturity. Second, the inner, originally nacreous shell layer of Bositra is now represented by neomorphic calcite that is luminescent, enriched in Mn and depleted in Mg, indicating that this layer was not dissolved in the taphonomic active zone. Third, fibrous- acicular low-Mg calcite cements that characteristically coat Bositra in shell beds show blotchy luminescence and highly irregular Mg distribution, indicating that they were precipitated as high-Mg calcite cements. Fibrous-acicular cements in shell beds do not coat upward- facing sides of valves covered by a first phase of micrite whereas they fully coat elevated portions of the same valves. Therefore, they were precipitated at very high rates concurrently with micrite deposition in shelters. Nutrient-rich bottom currents thus simultaneously increased (1) Bositra survivorship by enhancing primary productivity and (2) cementation rate by renewal of saturation of pore waters in the taphonomic active zone at platform tops. In spite of the associati","PeriodicalId":55341,"journal":{"name":"Bollettino Della Societa Geologica Italiana","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2020-02-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"87316458","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Mass-transport deposits from the Toarcian of the Umbria-Marche-Sabina Basin (Central Italy)","authors":"A. Cipriani, C. Zuccari, Giulia Innamorati, M. Marino, F. M. Petti","doi":"10.3301/IJG.2019.14","DOIUrl":"https://doi.org/10.3301/IJG.2019.14","url":null,"abstract":"Mass-transport deposits (MTDs) intercalated in slope/basinal successions, produced by submarine collapses and mass flows, are generally constituted of allochthonous elements sourced from platform margins. Here we present a noticeable exception where Toarcian calciclastic deposits made of pelagic carbonate elements are embedded in other pelagic carbonates. Selected outcrops pertaining to the Rosso Ammonitico Fm of three different pelagic carbonate platform (PCP)-basin systems were studied. The pelagic successions of the study areas onlap Early Jurassic structural highs. These clastic bodies partially replace the typical Toarcian reddish marls and shales of the Umbria-Marche-Sabina palaeogeographic Domain at different stratigraphic levels. The clasts range from blocks to megablocks; extraclasts of Corniola facies (Pliensbachian) and, sporadically, of Calcare Massiccio peritidal carbonates (Hettangian) are associated with Rosso Ammonitico intraclasts.The internal architecture of the MTDs and their emplacement processes, as well as their source and accumulation areas, were identified. Three distinct lithofacies characterise the clastic bodies, each one corresponding to a different emplacement process or to a different portion of the flow. The occurrence of lithified megablocks (>20 m across) of Corniola Fm suggests the exhumation of the buried portion of the unit. Synsedimentary extensional tectonics is the most likely triggering mechanism.Sedimentological analysis, coupled with geological mapping of the study areas, reveals the key role played by PCPs in the genesis of these MTDs. The early Toarcian reactivation of Hettangian palaeofaults bounding the structural highs is inferred. These faults, characterised by moderate offsets, crosscut the onlap wedges of the hangingwall successions, exhuming the older and lithified portion of Corniola Fm. Once become inactive, the fault planes were then eroded producing palaeoescarpments. Their backstepping, coupled with seismic shocks, produced the accumulation of the study clastic bodies.","PeriodicalId":55341,"journal":{"name":"Bollettino Della Societa Geologica Italiana","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2020-02-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"85442348","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Elemental and Sr-isotope characterization of the high-altitude Bosa vineyard in the Apuan Alps UNESCO Global Geopark (Italy)","authors":"L. Ghezzi, R. Petrini, F. Castorina, C. Scotti, G. Ottria, A. Bartelletti","doi":"10.3301/IJG.2019.20","DOIUrl":"https://doi.org/10.3301/IJG.2019.20","url":null,"abstract":"The Sr-isotope systematics and trace element analysis were applied to vine and wine collected during the 2015 harvest from the Bosa vineyard, a high-altitude farm in the Apuan Alps UNESCO Global Geopark in Italy, in order to investigate the links with geology in vineyards facing with a hostile environment. The results indicate a correspondence between the 87Sr/86Sr ratio in wine and must [87Sr/86Sr = 0.70843(1) and 0.70846(1), respectively] and the NH4OAc extractable Sr from soil [87Sr/86Sr = 0.70847(1)]. However, detailed investigations reveal that Sr-isotope data on grape juice collected in different vines vary in the range between 0.70833(1) and 0.70844(1), reflecting a small-scale vineyard variability and indicating that the root system explores heterogeneous soil resources for nutrient uptake. Grape seeds and stems from one single vine both show identical 87Sr/86Sr of 0.70820(1), significantly lower with respect to corresponding juice [87Sr/86Sr=0.70844(1)]: this finding is unexpected and reflects the uptake from isotopically different reservoir during the evolved dynamic of vine and fruit development. In particular, the lower 87Sr/86Sr ratio is attributed to the minor contribution of an unradiogenic carbonate component. These effects, however, do not mask the existing isotopic relationship between soil and wine at the vineyard scale. Trace elements in wine show a characteristic pattern that roughly mimics bedrock, suggesting a minor role of bedrock chemical weathering in developing the soil profile. Relatively high Fe and Mn contents are measured in wine, inherited from bedrocks, and high Zn, possibly applied to grapevines. Elements that are considered potentially toxic (As, Cd, Cu, Pb, Zn) are below the maximum acceptable limits established by OIV.Despite preliminary, these data represent the first characterization for traceability of the high-altitude Bosa vineyard, giving some track of weathering and elemental availability in a particular microclimate setting and underlying the link between bedrock geology and element uptake in vines at high elevations with respect to valley grown grapes.","PeriodicalId":55341,"journal":{"name":"Bollettino Della Societa Geologica Italiana","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2020-02-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"77531168","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Mesozoic tectono-sedimentary evolution of the Trapanese SouthernTethyan margin (NW Sicily) integrating facies and stratigraphic analysis with subsidence history","authors":"L.uca Basilone","doi":"10.3301/IJG.2019.19","DOIUrl":"https://doi.org/10.3301/IJG.2019.19","url":null,"abstract":"Several Mesozoic successions of the Southern Tethyan margin were accumulated on a carbonate platform evolving to pelagic plateau depositional systems. Rifting paleotectonics was the main process conditioning their tectono-sedimentary evolution. The well-exposed outcrops in the NW Sicilian fold and thrust belt of the so-called Trapanese carbonate platform to pelagic succession highlight the occurrence of lateral facies and thickness changes, paleofaults, volcanics, and resedimented deposits. The integration of facies analysis, stratigraphic data, and subsidence history have permitted to decipher the polyphase tectono-sedimentary evolution and to distinguish different depositional settings. Structural lows, filled with up to 100m of pillow lavas and reworked deposits, appear as intraplatform basins bordered by structural highs, as horst ridges, characterised by condensed sedimentation, and isolated seamounts. These sectors were linked among them by stepped fault margins, scalloped margins and depositional slopes. The tectonic history, highlighted by the backstripped sections, reveals superimposed evolutionary stages reflecting rifting and rapid tectonic subsidence, leading to continental break-up (Late Triassic-Early Jurassic stage); the Middle Jurassic stage reflects slow thermal subsidence in the basin shoulders and higher rates in the intervening depressions; the Late Jurassic-Early Cretaceous regional uplift interrupts the thermal subsidence curve trend. The tract of the Late Cretaceous-Eocene curve suggests again slow thermal post-rift subsidence, also influenced by sediment load. The different subsidence curves, reconstructed from different positions in the sedimentary basin, demonstrate that its evolution could be driven by the identified syn-sedimentary faults that were formed and/or re-activated during several tectonic events encompassing the whole Jurassic-Cretaceous time period. The regional significance of this tectonics indicates that the Sicilian sector of the Southern Tethyan continental margin was tectonically active for the whole Mesozoic.The reconstructed paleophysiography of the Trapanese continental margin, during the Mesozoic, appears characterised by a segmented and drowned carbonate platform with morphostructural highs separated by deep channels. The comparison with the present-day morphostructural setting of some regions of the Atlantic continental margins (e.g. Caribbean, Brazilian equatorial margin), suggests also for the study region that the occurrence of transcurrent/transform faults and stretching of the continental lithosphere can have played an important role in determining the physiographic conformation.","PeriodicalId":55341,"journal":{"name":"Bollettino Della Societa Geologica Italiana","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2020-02-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"77086704","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Seismic imaging of the shallow and deep structures in the Ancona landslide area","authors":"F. Accaino, L. Baradello, R. Nicolich, Alessandro Affattato","doi":"10.3301/ijg.2019.22","DOIUrl":"https://doi.org/10.3301/ijg.2019.22","url":null,"abstract":"Following the large 1982 Ancona landslide, which affected a densely populated district with many man-made infrastructures, a big effort was made by the scientific community to study the area and a great amount of geophysical and geotechnical data were acquired. The region is part of the external domain of Central Apennine resulted by Neogene compressive deformations. The tectonic processes have resulted in instabilities along the entire central Adriatic coasts of Italy, marked today by large-scale gravitational phenomena. An early Pleistocene regional uplift formed a slope subject to glacioeustatic sea-level oscillations, with erosion and water infiltration, favouring instability and movements under the action of gravitational driving forces. Sliding surface formation and roto-translational displacements have occurred until the recent reactivations of earth-flows and chaotic mounds at the slope break in correspondence with the formation of the Peri-Adriatic basin. In this paper, we present images of seismic sections obtained from the processing of two sea-land reflection profiles and offshore very high-resolution prospecting. Our paper intends to reinforce the importance of a multi-disciplinary approach integrating geophysical data to geological, morphological and engineering methods. The seismic survey of the two sea-land sections considered a joint land–sea acquisition to image the subsurface in the transitional zone. Composite sections were obtained from the processing of differently recorded sub-datasets, which depended on the type of land and marine sources and sensors in combination with the unique frequency content, source strength and noise, such as the propagation of surface-waves or air-gun bubbles. The properly acquired and processed data yielded post-stack migrated depth converted seismic sections, reflecting interfaces down to approximately 1400 m depth, where the top of Messinian evaporites has been encountered. The final sections reveal the deep structural settings and the importance of the still active anti-Apennine transfer faults.The offshore Boomer high-resolution profiles show only the near sea-bottom sequences. These fluvio-deltaic Plio-Quaternary deposits represent the final filling phase of the foreland basins, exposed to sub-aerial erosion during the last glacial period and to submersion during the subsequent sea-level rise of approximately 120 m.The final sections reveal the deep structural settings and the importance of the still active anti-Apennine transfer faults.","PeriodicalId":55341,"journal":{"name":"Bollettino Della Societa Geologica Italiana","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2020-02-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"86540836","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Esperienze educative alla mostra Cristalli ai Raggi X: il gesso di Vezzano sul Crostolo (RE)","authors":"M. Scacchetti, Milena Bertacchini","doi":"10.3301/rol.2018.26","DOIUrl":"https://doi.org/10.3301/rol.2018.26","url":null,"abstract":"The General Assembly of the United Nations declared 2014 the International Year of Crystallography, after 100 years from the awarding of the first Nobel Prize for the discovery of X-ray diffraction by crystals. On this occasion, the Department of Chemical and Geological Sciences of Modena and Reggio Emilia University (Italy)and its Museum “Gemma 1786”, organized an exhibition named Cristalli ai raggi X (Modena, 24 Jan.-29 Mar. 2015). The initiative involved the cooperation of many public and private partners and the active participation of twenty schools of different types and levels. An innovative aspect was the planned participation of highschool students to the fifty collateral events organized during the exhibition. The main purpose of Cristalli ai raggi X was to introduce non-specialists to the world of crystals and their properties, and to show how crystallography plays a role in the development of scientific disciplines. The display ended with the appreciation of 9,000 visitors and a hundred of guided tours for regional and extra-regional schools.The activity developed by the Manini Middle School of Vezzano sul Crostolo (Reggio Emilia province) involved 27 students of 13thyear-old. During an exhibition event opened to the public, they presented a study on the features of gypsum and the extraction history of the land where they come from and where, in the past, the gypsum was an important economic resource.","PeriodicalId":55341,"journal":{"name":"Bollettino Della Societa Geologica Italiana","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2018-07-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"86527315","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Structural setting, kinematics and metamorphism in a km-scale shear zone in the Inner Nappes of Sardinia (Italy)","authors":"C. Montomoli, S. Iaccarino, M. Simonetti, M. Lezzerini, R. Carosi","doi":"10.3301/IJG.2018.16","DOIUrl":"https://doi.org/10.3301/IJG.2018.16","url":null,"abstract":"In continental collisional orogenic belts, the hinterland-foreland transition plays a crucial role in the deformation styles and in the exhumation modes of the middle crustal rocks. The Barbagia Thrust (BT), a regional scale shear zone in the Variscan belt of central Sardinia, represents this transition. The BT, separating nappes withdifferent deformation styles, is still poorly characterized.We present new data of the BT and of the nearby tectonic units, using a multidisciplinary approach. We characterized in detail both meso- and micro-structural features, as well as, the metamorphic conditions with the aid of illite and chlorite “crystallinity” of rocks from the footwall, hanging wall and high-strain zone of the BT. Moreover, combining different palaeopiezometer-wet quartzite flowlaw pairs we characterized the rheological parameters (i.e., flow stress and strain rate) present during the BT activity. Three main deformation phases were recognized. After a D1 contractional deformation, a D2 related to the BT movement was associated to the development of a nearly 100 m thick high-strain zone withthe development of a mylonitic foliation, Sm, at middle crustal conditions, near the brittle-ductile” transition. Metamorphic constrains obtained from the footwall, the hanging wall and the high-strain zone supported an epizonal metamorphism with no unambiguous trend related to the strain intensity.Integrating our new metamorphic, deformation and rheological data, with previous ones in the geological literature helps to better unravel the long-lasting history of the nappe emplacement at hinterland-foreland transition in the Sardinian Variscan Belt.","PeriodicalId":55341,"journal":{"name":"Bollettino Della Societa Geologica Italiana","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2018-06-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"86832779","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}