The production of Z 0 bosons at large rapidities in Pb-Pb collisions at √ s NN = 5.02 TeV is repo... more The production of Z 0 bosons at large rapidities in Pb-Pb collisions at √ s NN = 5.02 TeV is reported. Z 0 candidates are reconstructed in the dimuon decay channel (Z 0 → μ + μ −), based on muons selected with pseudo-rapidity −4.0 < η < −2.5 and p T > 20 GeV/c. The invariant yield and the nuclear modification factor, R AA , are presented as a function of rapidity and collision centrality. The value of R AA for the 0-20% central Pb-Pb collisions is 0.67 ± 0.11 (stat.) ± 0.03 (syst.) ± 0.06 (corr. syst.), exhibiting a deviation of 2.6σ from unity. The results are well-described by calculations that include nuclear modifications of the parton distribution functions, while the predictions using vacuum PDFs deviate from data by 2.3σ in the 0-90% centrality class and by 3σ in the 0-20% central collisions.
The Upper Triassic depositional scenario of the Southern Alps was characterized by a widespread c... more The Upper Triassic depositional scenario of the Southern Alps was characterized by a widespread carbonate platform (Dolomia Principale) which during the Late Norian started to be distrupted by normal faults, linked to the Norian rifting phase. A number of intra-platform basins, where the deposition of dysoxic sediments took place, developed on the future Southalpine passive margin during this time. The primary objective of this note is to describe the depositional environment and the palaeogeography of a large Norian bioherm located within a small basin, in the Southern Alps central sector (Brescian Prealps, Lombardian domain). The domal bioherm (M. Zenone) developed on top of a tilted platform block of Dolomia Principale and progressively divided the original basinal environment into two small and elongated sub-basins. The bioherm started to growth on both carbonate ramp deposits (Dolomia Principale lower member) and muddy basinal sediments (Zorzino Limestone), and is followed by a complex serpulid-Tubiphytes bindstone and framestone. Steep clinostratified breccia bodies, downlapping the basinal deposits, are recognized on the western slope of the bioherm; conversely, on the eastfacing side the lateral relationship with the basinal areas shows a more gentle transition, proving the existence of a clear asymmetry of the paleorelief. Microfacies analysis reveal that the internal cavities of the encrusting organisms framework are relatively poor of carbonate mud, either asported by relatively deep currents, more efficient around the relief of the bioconstrution than in the surrounding basins, or retained in the nearby platform areas where the deposition of the Upper Dolomia Principale continued. Multiple phases of marine cementation allowed to build a reef-like framework and stabilized the bioherm. According to the geometry relationships between the clinostratified breccia slopes, the basinal deposits and the position of the platforms edges, the paleobathimetry of the bioherm and of the intervening basins can be estimated in 200 m and 600 m respectively.
The starting point of this work is to review the state of scientific knowledge of a sector that h... more The starting point of this work is to review the state of scientific knowledge of a sector that has probably received less attention than other areas of the central-western Dolomites and which corresponds to the Biois and Cordevole torrents Lower Ladinian Basin, delimited to the north from the Marmolada – Costabella Group, to the east from the Alto di Pelsa (Mt. Civetta Group) and to the south from the Pale di San Lucano (Pale di San Martino Group). Therefore, an attempt was made to combine the data and information present in the literature with new observations both on a macroscopic scale (description of carbonate complexes) and in detail through the analysis and measurement of many basin stratigraphic sections, some already proposed previously. by the authors and other unpublished ones. In particular, some stratigraphic sections have been revised and an attempt has been made to quantify the volumes of the re-sedimented deposits in the basin based on their texture, as already done previously for the stratigraphic succession of Rio Bordina (Trombetta & Masetti, 2012); the next step was to correlate the texture and thickness of the basin deposits with the geometry of the carbonate complexes and with the inclination of the clinoforms within them in order to review the evolution models of the carbonate platforms surrounding the Biois river basin. The facies analysis conducted on the Livinallongo Formation basin sequences showed that the greatest lateral variability is recorded within the Bänderkalke member, while the lower and middle members – Plattenkalke and Knollenkalke – appear more uniform
The Costabella – Cima Uomo – Palon de Jigole – Col Becher montain group represents the Southern m... more The Costabella – Cima Uomo – Palon de Jigole – Col Becher montain group represents the Southern margin of Marmolada carbonate platform complex. The study of the any sedimentary successions shows a marked lateral variability of the Livinallongo Formation that may be not explaned only with proximal/distal from the source areas; a second factor that affects this lateral variability may be Upper Anisian – Lower Ladinian palaeogeographic setting of this Dolomite sector. The " calcari rossi " member (Palon de Jigole section/Passo delle Cirelle) represents an " high relative zone " between the Lower Ladinian platform nuclei and the basin areas where has recorded the three member of the Livinallongo Formation. The Val Ombretta was a slope area closed at the carbonate platform (Sciliar Formation). The Colle di Santa Lucia/Caprile section, near at the others sedimentary successions, was outside of the carbonate platform influence (Marmolada and Mt. Alto di Pelsa) and located into the Cadore Basin characterized by huge volume of volcanoclastic risedimentation (Pietra Verde).
Il sistema di piattaforma carbonatica del Settsass/Richthofen Riff, assieme ad altri complessi ca... more Il sistema di piattaforma carbonatica del Settsass/Richthofen Riff, assieme ad altri complessi carbonatici post-vulcanici contribuisce a definire il quadro paleogeografico di età Carnico inferiore delle Dolomiti Occidentali. Queste piattaforme del Carnico inferiore erano popolate da patchreefs a coralli e mounds a spugne separati da piccole lagune caratterizzate da sedimentazione fangosa (micrite). Il Settsass/Richthofen Riff è un piccolo sistema di piattaforma carbonatica (3-4 Km2 di estensione per circa 150 m di spessore) ed è caratterizzato dalla sovrapposizione da due edifici di piattaforma (DC1 e DC2) che mostrano differente forma geometrica: a) l’edificio inferiore, conosciuto come Richthofen Riff (DC 1), mostra una geometria piano-convessa il cui nucleo è costituito da patch-reef a coralli e mound a spugne, mentre le parti laterali sono rappresentate da depositi di scarpata interdigitati con i depositi bacinali (Formazione di San Cassiano); b) il complesso carbonatico superiore, cioè il rilievo del Settsass (DC 2), mostra una geometria tabulare e/o che si ispessisce leggermente verso il bacino (thickening basinward). Questo complesso superiore conserva al suo interno differenti ambienti deposizionali che variano dai depositi di piattaforma interna (back-reef), del versante sud-occidentale, a quelli di slope registrati lungo il versante sud-orientale del Settsass. I depositi di slope sono costituiti da brecce clinostratificate con angoli di slope variabili da 20°-25°, nelle aree prossimali, a 10°-15° in quelle distali. Il complesso di piattaforma del Settsass mostra una progradazione verso il bacino che può essere seguita in affioramento per circa 2 km. Parole chiave: piattaforme carbonatiche, Dolomia Cassiana, reefs a Coralli, mounds a spugne, clinoformi, progradazione, Triassico, Regione Dolomitica, Alpi Meridionali. Abstract Facies analysis and architecture of a Carnian carbonate platform: the Settsass/Richthofen Riff (Dolomites, Southern Alps, Northern Italy). The Settsass/Richthofen Riff carbonate platform system, together with the other central-western Dolomites post-volcanic carbonate complexes, forms the palaeogeographic scenario of the Lower Carnian age. These Lower Carnian platforms were dwelled by coral patch-reefs and sponge mounds separated by small lagoons characterized by muddy sedimentation. The Settsass/Richthofen Riff is a small platform system (3-4 km2 in plain view and about 150 m thick) and is characterized by two superimposed carbonate complexes (DC 1 and DC 2) showing different geometric features: a) the lower complex, known as the Richthofen Riff (DC 1), shows a plane-convex geometry where the core is constituted by coral patch-reefs and sponge bodies, while the lateral portion is represented by the slope sediments interfingering with the basinal deposits (San Cassiano Formation); b) the upper complex, the proper Settsass relief (DC 2), shows a tabular geometry and/or some thickening basinward. This upper complex covers a variety of depositional settings, from inner platform deposits (back-reef ) at the southwestern side, to slope deposits at the southeastern side. Its slope deposits are formed by clinostratified breccias with slope angles ranging from 20° - 25° in the proximal area, to 10° - 15° more distally. The Settsass platform complex shows a basinward progradation (NE direction) which can be traced in outcrops for almost 2 km. Keywords: Carbonate platforms, Cassian Dolomite, Sponges and Coral-reefs, clinoforms, progradation, Triassic, Dolomites Region, Southern Alps
Abstract: The Norian sequence cropping out between Lake Garda and Lake Idro recflects the local b... more Abstract: The Norian sequence cropping out between Lake Garda and Lake Idro recflects the local basinal sedimentary evolution responding to tectonic events. These control both the basin geometry and structural character, and the evolution of the carbonate platforms surrounding these basins. The investigated area includes the intra-platform basins West of Lake Garda formed as a result of the Norian spreading phase along the future margin of the Lombardian Basin. This paper will focus on the Magasa-Capovalle Basin, composed of two graben separated by a carbonate platform horst, corresponding to Mt. Cingla, Mt. Pralta and Mt. Chenzere. The sedimentation in these graben is controlled by the evolution of the marginal platforms. These marginal platforms correspond on the Dolomia Principale deposits, here informally divided in two different units: a) a lower member (Valvestino member) is organized in shallowing-upward cycles mainly constituted by subtidal deposits; the depositional environment is referred to a carbonate ramp linking the Trento Platform to the deeper environment of the Lombardian area. This member is found below both the basinal and the platform areas; b) the upper member (Dosso delle Saette member), organized in shallowing upward cycles as well, is characterized by higher energy facies than the Valvestino member and is referred to less deep bathymetric conditions. This member is found on the “structural highs” originated by the Norian extensional phase. In the northern sector (Magasa graben) the basinal succession is made up of clinoforms composed of breccias which interfinger down dip with basinal dolomicrite and doloarenite sediments. At this location it is possible to recognize packages of beds exhibiting a sedimentary cyclicity expressed by beds which thicken and coarsen upward within the individual cycles. The thinnest and finest base of the cycles is basinal in original while the upper thicker and coarser beds are the down-dip edges of the clinoforms. In the middle of the basin, the Mt. Pralta represents a key to understand the tectonic-sedimentary evolution. In fact, its northern part is constituted by a carbonate platform while the southern side is characterized by a thick body of basinal sediments (called “facies eteropiche” della Dolomia Principale). These two different sedimentary deposits are divided by a palaeo-fault with an E-W trend and southern dip, sealed by the basinal sediments of the Zorzino Limestone. This latter represents the drowning event of the carbonate platform horst of the Mt. Pralta. In the south-western sector (Capovalle area) the sedimentary sequence is composed by a thick body of megabreccias (about 140 m), followed by the deposition of the Zorzino Limestone. In this formation it is possible to distinguish a lower member, showing the sedimentary cyclicity discussed above (about 140 m), a middle micritic member (300 m) and an upper member exhibiting sedimentary cycles similar to those of the lower member, but finer in texture (about 200 m). In the northern area the sediments “infilling” are coarser because the marginal platform (Dosso delle Saette) keeps exporting carbonate sediments down into the basin until the deposition of the Riva di Solto Shale. On the other hand (Capovalle) the southern marginal platforms drowns earlier than in the northern area and is followed by the basinal sediments of the Zorzino Limestone. This drowning event is shown at Mt. Manos and Mt. Carzen. This palaeo-morphology linked to the extensional phase developed in the Norian, becomes finally “frozen” by the Rhaetian transgressive event, when the deposition of the Riva di Solto Shale capped the sequence and filled the low adjacent areas.
During the late Ladinian the Western Dolomites were strongly influenced by a tectonic phase linke... more During the late Ladinian the Western Dolomites were strongly influenced by a tectonic phase linked to the dismantlement of the volcanic edifices of the Predazzo – Monzoni magmatic district, causing the discharge of large amounts of volcanoclastic sediments. The synchroneity of the tectonic events, and the deposition of huge volumes of volcanic sediments, represents the main cause of the facies and thickness changes. These changes are recorded in post-volcanic sequences (marmolada Conglomerate and Wengen Formation). In the Col Rossi – Porta Vescovo area the sedimentary substrate was affected by a N-S fault set which bounded, in the Penia – Canazei area, a small collapsed sector. In this area a thicker Ladinian – Carnian basinal succession has been recorded. This complex paleogeography was filled with the deposition of the volcanic, volcanoclastic and, subsequently, post-volcanic successions.
Key words: Stratigraphy, Upper Ladinian, tectonics, normal faults, Western Dolomites
During the late Ladinian the Western Dolomites were strongly influenced by a tectonic phase linke... more During the late Ladinian the Western Dolomites were strongly influenced by a tectonic phase linked to the dismantlement of the volcanic edifices of the Predazzo – Monzoni magmatic district, causing the discharge of large amounts of volcanoclastic sediments. The synchroneity of the tectonic events, and the deposition of huge volumes of volcanic sediments, represents the main cause of the facies and thickness changes. These changes are recorded in post-volcanic sequences (marmolada Conglomerate and Wengen Formation). In the Col Rossi – Porta Vescovo area the sedimentary substrate was affected by a N-S fault set which bounded, in the Penia – Canazei area, a small collapsed sector. In this area a thicker Ladinian – Carnian basinal succession has been recorded. This complex paleogeography was filled with the deposition of the volcanic, volcanoclastic and, subsequently, post-volcanic successions.
Key words: Stratigraphy, Upper Ladinian, tectonics, normal faults, Western Dolomites
The Conglomerato della Marmolada is a volcaniclastic succession consisting of conglomerates and s... more The Conglomerato della Marmolada is a volcaniclastic succession consisting of conglomerates and sandstones accumulated in the basinal area comprised among the lower Ladinian carbonate platforms of the Dolomia dello Sciliar and Calcare della Marmolada (central-western Dolomites). The Conglomerato della Marmolada was deposited at the end of the Ladinian magmatic activity affecting the central-western Dolomites when the strong erosional phase, leading to the complete and quick dismantling of the magmatic districts edifices (Predazzo and Monzoni), started. The Col Rossi – Porta Vescovo Range, our investigation area, is a portion of this basin where the erosion phase's products were deposited, and it is represented mainly by a thick succession of the Conglomerato della Marmolada (with thicknesses variable from 400 to 900 m). This succession consists of two fining-upward sedimentary sequences recording a two-phases basinal filling; the first phase, characterized by differential subsidence conditions, is controlled by synsedimentary extensive faults and is responsible for the wedge-shaped geometry of the basic sequence. The second phase, represented by a sequence with uniform thickness and tabular shape, testifies the progressive filling produced by the supply of finer sediments in an uniform subsidence regime over the entire studied area. Inside this sequences several fining-up decametric scale cycles have been recognized, whose deposition occurred by means gravity flows (debris-flows and high-density turbulent flows) into a tectonically-controlled small basin. These gravity flows were produced by high-density and frequent erosional phases occurring in the subaerial volcanic source areas. The Conglomerato della Marmolada sedimentary environment is here interpretated as a high-density turbiditic system driven to catastrophic events.
During the last 20 years, many exceptional fossiliferous levels have been discovered in the Upper... more During the last 20 years, many exceptional fossiliferous levels have been discovered in the Upper Triassic of Lombardy, Northern Italy. The assemblages mainly comprise superbly preserved arthropods, vertebrate skeletons in anatomical connection, and also rare soft bodied organisms. Invertebrates are represented by worms, molluscs, crustaceans, insects and echinoderms, whereas vertebrates include fish and reptiles. The associations are comprised of both continental and marine organisms, and reveal many previously unknown taxa. This paper is an attempt to produce a palaeoenvironmental interpretation of these faunae, through the integration of sedimentological and palaeontological data. The fossiliferous associations are preserved both within calcareous balck shales (part of the Zorzino Limestone) and in younger laminated claystones (Riva di Solto Shale lower part, “Rhaetic Facies”). The older fossiliferous associations were preserved during a carbonate depositional phases characterized by emerging areas, large stromatolitic tidal flats, shallow platform lagoons and marginal reefs. The reefs were dominated by algae, serpulid worms and other encrusting organisms and flanked by narrow, poorly oxigenated intraplatform depressions. The fossiliferous beds deposited within these depressions contain mainly nectonic crustaceans and bony fishes. The majority of these faunae adapted to reef environment, but lagoon and terrestrial organisms are also included. Vertebrate associations show some of the most ancient known flying reptiles. The ecological compositionof the continental vertebrate faunas was probably similar to that of modern tropical keys.
The Upper Triassic depositional scenario of the Southern Alps was characterized by a widespread c... more The Upper Triassic depositional scenario of the Southern Alps was characterized by a widespread carbonate platform (Dolomia Principale) which during the Late Norian started to be distrupted by normal faults, linked to the Norian rifting phase. A number of intra-platform basins, where the deposition of dysoxic sediments took place, developed on the future Southalpine passive margin during this time. The primary objective of this note is to describe the depositional environment and the palaeogeography of a large Norian bioherm located within a small basin, in the Southern Alps central sector (Brescian Prealps, Lombardian domain). The domal bioherm (M. Zenone) developed on top of a tilted platform block of Dolomia Principale and progressively divided the original basinal environment into two small and elongated sub-basins. The bioherm started to growth on both carbonate ramp deposits (Dolomia Principale lower member) and muddy basinal sediments (Zorzino Limestone), and is followed by a complex serpulid-Tubiphytes bindstone and framestone. Steep clinostratified breccia bodies, downlapping the basinal deposits, are recognized on the western slope of the bioherm; conversely, on the eastfacing side the lateral relationship with the basinal areas shows a more gentle transition, proving the existence of a clear asymmetry of the paleorelief. Microfacies analysis reveal that the internal cavities of the encrusting organisms framework are relatively poor of carbonate mud, either asported by relatively deep currents, more efficient around the relief of the bioconstrution than in the surrounding basins, or retained in the nearby platform areas where the deposition of the Upper Dolomia Principale continued. Multiple phases of marine cementation allowed to build a reef-like framework and stabilized the bioherm. According to the geometry relationships between the clinostratified breccia slopes, the basinal deposits and the position of the platforms edges, the paleobathimetry of the bioherm and of the intervening basins can be estimated in 200 m and 600 m respectively.
The San Lucano Valley is located in the Western Dolomite southern sector where the Triassic sedim... more The San Lucano Valley is located in the Western Dolomite southern sector where the Triassic sedimentary succession exceed 2000 m in thickness. In the Rio Bordina valley outcrops a sedimentary succession from the Lower Triassic to Upper Ladinian age including the Moena and Livinallongo basinal formations. The high percentage of the coarse grain like turbidite deposits (cal-carenites or doloarenites and sedimentary breccias) may be interpreted with high rate production and exportatiton from the surrounding carbonate platforms and the high subsidence rate of this Dolomite sector. The neighbouring platforms are represented by the Contrin Formation and the Sciliar Formation; the first one has characterized by a tabular feature while the second one shows a plano-convex geometry as a classic bioconstructed carbonate build-up.
This paper analyses the whole of the Rhaetic facies outcropping in Umbria and Eastern Toscany and... more This paper analyses the whole of the Rhaetic facies outcropping in Umbria and Eastern Toscany and traditionally referred to as Toscan nappe and the Umbrian Units. These facies were deposited on a gently stepping sea floor dominated by storms and are referred to as Formazione del Monte Cetona. This unit is subdivisible in a lower marly member and in an upper carbonate member. The lower unit is characterized by asymmetric thickening up cycles, that show an upward enrichment in carbonate from basal marls to pure limestones at the top. Mud-dominated cycles were common in the deeper portion of the basin while grainy cycles were developed in shallower setting. The calcarenites cycles clearly show a coarsening upward evolution from marly and carbonate mud at the base to coarse bioclastic or oolitic calcarenites at the top. This coarsening evolution was mainly produced by an increase in storm-wave reworking, during a shallowing up evolution, but sometimes tide currents were important. Also in the upper carbonate member there are coarsening and shallowing up cycles, but they are less evident because the lack of a marly base and the widespread dolomitization and recrystallization. At the base of the upper member there are sometimes encrusting biostromes with a plane-convex shape. These small build-ups show a cyclic pattern, probably related to bathymetric fluctuations. Tectonic deformations severally affected the base of the Rhaetic and the underlying formations, but the bottom of the Rhaetic succession clearly marked a generalized deepening testified by the deposition of rather deep marine facies over older sabkha evaporites. This deepening episode was followed by a global shallowing upward evolution, towards evolution, towards the medium portion of the upper member. After a smaller re-deepening, the Rhaetic succession ends with shallow water carbonates.
The production of Z 0 bosons at large rapidities in Pb-Pb collisions at √ s NN = 5.02 TeV is repo... more The production of Z 0 bosons at large rapidities in Pb-Pb collisions at √ s NN = 5.02 TeV is reported. Z 0 candidates are reconstructed in the dimuon decay channel (Z 0 → μ + μ −), based on muons selected with pseudo-rapidity −4.0 < η < −2.5 and p T > 20 GeV/c. The invariant yield and the nuclear modification factor, R AA , are presented as a function of rapidity and collision centrality. The value of R AA for the 0-20% central Pb-Pb collisions is 0.67 ± 0.11 (stat.) ± 0.03 (syst.) ± 0.06 (corr. syst.), exhibiting a deviation of 2.6σ from unity. The results are well-described by calculations that include nuclear modifications of the parton distribution functions, while the predictions using vacuum PDFs deviate from data by 2.3σ in the 0-90% centrality class and by 3σ in the 0-20% central collisions.
The Upper Triassic depositional scenario of the Southern Alps was characterized by a widespread c... more The Upper Triassic depositional scenario of the Southern Alps was characterized by a widespread carbonate platform (Dolomia Principale) which during the Late Norian started to be distrupted by normal faults, linked to the Norian rifting phase. A number of intra-platform basins, where the deposition of dysoxic sediments took place, developed on the future Southalpine passive margin during this time. The primary objective of this note is to describe the depositional environment and the palaeogeography of a large Norian bioherm located within a small basin, in the Southern Alps central sector (Brescian Prealps, Lombardian domain). The domal bioherm (M. Zenone) developed on top of a tilted platform block of Dolomia Principale and progressively divided the original basinal environment into two small and elongated sub-basins. The bioherm started to growth on both carbonate ramp deposits (Dolomia Principale lower member) and muddy basinal sediments (Zorzino Limestone), and is followed by a complex serpulid-Tubiphytes bindstone and framestone. Steep clinostratified breccia bodies, downlapping the basinal deposits, are recognized on the western slope of the bioherm; conversely, on the eastfacing side the lateral relationship with the basinal areas shows a more gentle transition, proving the existence of a clear asymmetry of the paleorelief. Microfacies analysis reveal that the internal cavities of the encrusting organisms framework are relatively poor of carbonate mud, either asported by relatively deep currents, more efficient around the relief of the bioconstrution than in the surrounding basins, or retained in the nearby platform areas where the deposition of the Upper Dolomia Principale continued. Multiple phases of marine cementation allowed to build a reef-like framework and stabilized the bioherm. According to the geometry relationships between the clinostratified breccia slopes, the basinal deposits and the position of the platforms edges, the paleobathimetry of the bioherm and of the intervening basins can be estimated in 200 m and 600 m respectively.
The starting point of this work is to review the state of scientific knowledge of a sector that h... more The starting point of this work is to review the state of scientific knowledge of a sector that has probably received less attention than other areas of the central-western Dolomites and which corresponds to the Biois and Cordevole torrents Lower Ladinian Basin, delimited to the north from the Marmolada – Costabella Group, to the east from the Alto di Pelsa (Mt. Civetta Group) and to the south from the Pale di San Lucano (Pale di San Martino Group). Therefore, an attempt was made to combine the data and information present in the literature with new observations both on a macroscopic scale (description of carbonate complexes) and in detail through the analysis and measurement of many basin stratigraphic sections, some already proposed previously. by the authors and other unpublished ones. In particular, some stratigraphic sections have been revised and an attempt has been made to quantify the volumes of the re-sedimented deposits in the basin based on their texture, as already done previously for the stratigraphic succession of Rio Bordina (Trombetta & Masetti, 2012); the next step was to correlate the texture and thickness of the basin deposits with the geometry of the carbonate complexes and with the inclination of the clinoforms within them in order to review the evolution models of the carbonate platforms surrounding the Biois river basin. The facies analysis conducted on the Livinallongo Formation basin sequences showed that the greatest lateral variability is recorded within the Bänderkalke member, while the lower and middle members – Plattenkalke and Knollenkalke – appear more uniform
The Costabella – Cima Uomo – Palon de Jigole – Col Becher montain group represents the Southern m... more The Costabella – Cima Uomo – Palon de Jigole – Col Becher montain group represents the Southern margin of Marmolada carbonate platform complex. The study of the any sedimentary successions shows a marked lateral variability of the Livinallongo Formation that may be not explaned only with proximal/distal from the source areas; a second factor that affects this lateral variability may be Upper Anisian – Lower Ladinian palaeogeographic setting of this Dolomite sector. The " calcari rossi " member (Palon de Jigole section/Passo delle Cirelle) represents an " high relative zone " between the Lower Ladinian platform nuclei and the basin areas where has recorded the three member of the Livinallongo Formation. The Val Ombretta was a slope area closed at the carbonate platform (Sciliar Formation). The Colle di Santa Lucia/Caprile section, near at the others sedimentary successions, was outside of the carbonate platform influence (Marmolada and Mt. Alto di Pelsa) and located into the Cadore Basin characterized by huge volume of volcanoclastic risedimentation (Pietra Verde).
Il sistema di piattaforma carbonatica del Settsass/Richthofen Riff, assieme ad altri complessi ca... more Il sistema di piattaforma carbonatica del Settsass/Richthofen Riff, assieme ad altri complessi carbonatici post-vulcanici contribuisce a definire il quadro paleogeografico di età Carnico inferiore delle Dolomiti Occidentali. Queste piattaforme del Carnico inferiore erano popolate da patchreefs a coralli e mounds a spugne separati da piccole lagune caratterizzate da sedimentazione fangosa (micrite). Il Settsass/Richthofen Riff è un piccolo sistema di piattaforma carbonatica (3-4 Km2 di estensione per circa 150 m di spessore) ed è caratterizzato dalla sovrapposizione da due edifici di piattaforma (DC1 e DC2) che mostrano differente forma geometrica: a) l’edificio inferiore, conosciuto come Richthofen Riff (DC 1), mostra una geometria piano-convessa il cui nucleo è costituito da patch-reef a coralli e mound a spugne, mentre le parti laterali sono rappresentate da depositi di scarpata interdigitati con i depositi bacinali (Formazione di San Cassiano); b) il complesso carbonatico superiore, cioè il rilievo del Settsass (DC 2), mostra una geometria tabulare e/o che si ispessisce leggermente verso il bacino (thickening basinward). Questo complesso superiore conserva al suo interno differenti ambienti deposizionali che variano dai depositi di piattaforma interna (back-reef), del versante sud-occidentale, a quelli di slope registrati lungo il versante sud-orientale del Settsass. I depositi di slope sono costituiti da brecce clinostratificate con angoli di slope variabili da 20°-25°, nelle aree prossimali, a 10°-15° in quelle distali. Il complesso di piattaforma del Settsass mostra una progradazione verso il bacino che può essere seguita in affioramento per circa 2 km. Parole chiave: piattaforme carbonatiche, Dolomia Cassiana, reefs a Coralli, mounds a spugne, clinoformi, progradazione, Triassico, Regione Dolomitica, Alpi Meridionali. Abstract Facies analysis and architecture of a Carnian carbonate platform: the Settsass/Richthofen Riff (Dolomites, Southern Alps, Northern Italy). The Settsass/Richthofen Riff carbonate platform system, together with the other central-western Dolomites post-volcanic carbonate complexes, forms the palaeogeographic scenario of the Lower Carnian age. These Lower Carnian platforms were dwelled by coral patch-reefs and sponge mounds separated by small lagoons characterized by muddy sedimentation. The Settsass/Richthofen Riff is a small platform system (3-4 km2 in plain view and about 150 m thick) and is characterized by two superimposed carbonate complexes (DC 1 and DC 2) showing different geometric features: a) the lower complex, known as the Richthofen Riff (DC 1), shows a plane-convex geometry where the core is constituted by coral patch-reefs and sponge bodies, while the lateral portion is represented by the slope sediments interfingering with the basinal deposits (San Cassiano Formation); b) the upper complex, the proper Settsass relief (DC 2), shows a tabular geometry and/or some thickening basinward. This upper complex covers a variety of depositional settings, from inner platform deposits (back-reef ) at the southwestern side, to slope deposits at the southeastern side. Its slope deposits are formed by clinostratified breccias with slope angles ranging from 20° - 25° in the proximal area, to 10° - 15° more distally. The Settsass platform complex shows a basinward progradation (NE direction) which can be traced in outcrops for almost 2 km. Keywords: Carbonate platforms, Cassian Dolomite, Sponges and Coral-reefs, clinoforms, progradation, Triassic, Dolomites Region, Southern Alps
Abstract: The Norian sequence cropping out between Lake Garda and Lake Idro recflects the local b... more Abstract: The Norian sequence cropping out between Lake Garda and Lake Idro recflects the local basinal sedimentary evolution responding to tectonic events. These control both the basin geometry and structural character, and the evolution of the carbonate platforms surrounding these basins. The investigated area includes the intra-platform basins West of Lake Garda formed as a result of the Norian spreading phase along the future margin of the Lombardian Basin. This paper will focus on the Magasa-Capovalle Basin, composed of two graben separated by a carbonate platform horst, corresponding to Mt. Cingla, Mt. Pralta and Mt. Chenzere. The sedimentation in these graben is controlled by the evolution of the marginal platforms. These marginal platforms correspond on the Dolomia Principale deposits, here informally divided in two different units: a) a lower member (Valvestino member) is organized in shallowing-upward cycles mainly constituted by subtidal deposits; the depositional environment is referred to a carbonate ramp linking the Trento Platform to the deeper environment of the Lombardian area. This member is found below both the basinal and the platform areas; b) the upper member (Dosso delle Saette member), organized in shallowing upward cycles as well, is characterized by higher energy facies than the Valvestino member and is referred to less deep bathymetric conditions. This member is found on the “structural highs” originated by the Norian extensional phase. In the northern sector (Magasa graben) the basinal succession is made up of clinoforms composed of breccias which interfinger down dip with basinal dolomicrite and doloarenite sediments. At this location it is possible to recognize packages of beds exhibiting a sedimentary cyclicity expressed by beds which thicken and coarsen upward within the individual cycles. The thinnest and finest base of the cycles is basinal in original while the upper thicker and coarser beds are the down-dip edges of the clinoforms. In the middle of the basin, the Mt. Pralta represents a key to understand the tectonic-sedimentary evolution. In fact, its northern part is constituted by a carbonate platform while the southern side is characterized by a thick body of basinal sediments (called “facies eteropiche” della Dolomia Principale). These two different sedimentary deposits are divided by a palaeo-fault with an E-W trend and southern dip, sealed by the basinal sediments of the Zorzino Limestone. This latter represents the drowning event of the carbonate platform horst of the Mt. Pralta. In the south-western sector (Capovalle area) the sedimentary sequence is composed by a thick body of megabreccias (about 140 m), followed by the deposition of the Zorzino Limestone. In this formation it is possible to distinguish a lower member, showing the sedimentary cyclicity discussed above (about 140 m), a middle micritic member (300 m) and an upper member exhibiting sedimentary cycles similar to those of the lower member, but finer in texture (about 200 m). In the northern area the sediments “infilling” are coarser because the marginal platform (Dosso delle Saette) keeps exporting carbonate sediments down into the basin until the deposition of the Riva di Solto Shale. On the other hand (Capovalle) the southern marginal platforms drowns earlier than in the northern area and is followed by the basinal sediments of the Zorzino Limestone. This drowning event is shown at Mt. Manos and Mt. Carzen. This palaeo-morphology linked to the extensional phase developed in the Norian, becomes finally “frozen” by the Rhaetian transgressive event, when the deposition of the Riva di Solto Shale capped the sequence and filled the low adjacent areas.
During the late Ladinian the Western Dolomites were strongly influenced by a tectonic phase linke... more During the late Ladinian the Western Dolomites were strongly influenced by a tectonic phase linked to the dismantlement of the volcanic edifices of the Predazzo – Monzoni magmatic district, causing the discharge of large amounts of volcanoclastic sediments. The synchroneity of the tectonic events, and the deposition of huge volumes of volcanic sediments, represents the main cause of the facies and thickness changes. These changes are recorded in post-volcanic sequences (marmolada Conglomerate and Wengen Formation). In the Col Rossi – Porta Vescovo area the sedimentary substrate was affected by a N-S fault set which bounded, in the Penia – Canazei area, a small collapsed sector. In this area a thicker Ladinian – Carnian basinal succession has been recorded. This complex paleogeography was filled with the deposition of the volcanic, volcanoclastic and, subsequently, post-volcanic successions.
Key words: Stratigraphy, Upper Ladinian, tectonics, normal faults, Western Dolomites
During the late Ladinian the Western Dolomites were strongly influenced by a tectonic phase linke... more During the late Ladinian the Western Dolomites were strongly influenced by a tectonic phase linked to the dismantlement of the volcanic edifices of the Predazzo – Monzoni magmatic district, causing the discharge of large amounts of volcanoclastic sediments. The synchroneity of the tectonic events, and the deposition of huge volumes of volcanic sediments, represents the main cause of the facies and thickness changes. These changes are recorded in post-volcanic sequences (marmolada Conglomerate and Wengen Formation). In the Col Rossi – Porta Vescovo area the sedimentary substrate was affected by a N-S fault set which bounded, in the Penia – Canazei area, a small collapsed sector. In this area a thicker Ladinian – Carnian basinal succession has been recorded. This complex paleogeography was filled with the deposition of the volcanic, volcanoclastic and, subsequently, post-volcanic successions.
Key words: Stratigraphy, Upper Ladinian, tectonics, normal faults, Western Dolomites
The Conglomerato della Marmolada is a volcaniclastic succession consisting of conglomerates and s... more The Conglomerato della Marmolada is a volcaniclastic succession consisting of conglomerates and sandstones accumulated in the basinal area comprised among the lower Ladinian carbonate platforms of the Dolomia dello Sciliar and Calcare della Marmolada (central-western Dolomites). The Conglomerato della Marmolada was deposited at the end of the Ladinian magmatic activity affecting the central-western Dolomites when the strong erosional phase, leading to the complete and quick dismantling of the magmatic districts edifices (Predazzo and Monzoni), started. The Col Rossi – Porta Vescovo Range, our investigation area, is a portion of this basin where the erosion phase's products were deposited, and it is represented mainly by a thick succession of the Conglomerato della Marmolada (with thicknesses variable from 400 to 900 m). This succession consists of two fining-upward sedimentary sequences recording a two-phases basinal filling; the first phase, characterized by differential subsidence conditions, is controlled by synsedimentary extensive faults and is responsible for the wedge-shaped geometry of the basic sequence. The second phase, represented by a sequence with uniform thickness and tabular shape, testifies the progressive filling produced by the supply of finer sediments in an uniform subsidence regime over the entire studied area. Inside this sequences several fining-up decametric scale cycles have been recognized, whose deposition occurred by means gravity flows (debris-flows and high-density turbulent flows) into a tectonically-controlled small basin. These gravity flows were produced by high-density and frequent erosional phases occurring in the subaerial volcanic source areas. The Conglomerato della Marmolada sedimentary environment is here interpretated as a high-density turbiditic system driven to catastrophic events.
During the last 20 years, many exceptional fossiliferous levels have been discovered in the Upper... more During the last 20 years, many exceptional fossiliferous levels have been discovered in the Upper Triassic of Lombardy, Northern Italy. The assemblages mainly comprise superbly preserved arthropods, vertebrate skeletons in anatomical connection, and also rare soft bodied organisms. Invertebrates are represented by worms, molluscs, crustaceans, insects and echinoderms, whereas vertebrates include fish and reptiles. The associations are comprised of both continental and marine organisms, and reveal many previously unknown taxa. This paper is an attempt to produce a palaeoenvironmental interpretation of these faunae, through the integration of sedimentological and palaeontological data. The fossiliferous associations are preserved both within calcareous balck shales (part of the Zorzino Limestone) and in younger laminated claystones (Riva di Solto Shale lower part, “Rhaetic Facies”). The older fossiliferous associations were preserved during a carbonate depositional phases characterized by emerging areas, large stromatolitic tidal flats, shallow platform lagoons and marginal reefs. The reefs were dominated by algae, serpulid worms and other encrusting organisms and flanked by narrow, poorly oxigenated intraplatform depressions. The fossiliferous beds deposited within these depressions contain mainly nectonic crustaceans and bony fishes. The majority of these faunae adapted to reef environment, but lagoon and terrestrial organisms are also included. Vertebrate associations show some of the most ancient known flying reptiles. The ecological compositionof the continental vertebrate faunas was probably similar to that of modern tropical keys.
The Upper Triassic depositional scenario of the Southern Alps was characterized by a widespread c... more The Upper Triassic depositional scenario of the Southern Alps was characterized by a widespread carbonate platform (Dolomia Principale) which during the Late Norian started to be distrupted by normal faults, linked to the Norian rifting phase. A number of intra-platform basins, where the deposition of dysoxic sediments took place, developed on the future Southalpine passive margin during this time. The primary objective of this note is to describe the depositional environment and the palaeogeography of a large Norian bioherm located within a small basin, in the Southern Alps central sector (Brescian Prealps, Lombardian domain). The domal bioherm (M. Zenone) developed on top of a tilted platform block of Dolomia Principale and progressively divided the original basinal environment into two small and elongated sub-basins. The bioherm started to growth on both carbonate ramp deposits (Dolomia Principale lower member) and muddy basinal sediments (Zorzino Limestone), and is followed by a complex serpulid-Tubiphytes bindstone and framestone. Steep clinostratified breccia bodies, downlapping the basinal deposits, are recognized on the western slope of the bioherm; conversely, on the eastfacing side the lateral relationship with the basinal areas shows a more gentle transition, proving the existence of a clear asymmetry of the paleorelief. Microfacies analysis reveal that the internal cavities of the encrusting organisms framework are relatively poor of carbonate mud, either asported by relatively deep currents, more efficient around the relief of the bioconstrution than in the surrounding basins, or retained in the nearby platform areas where the deposition of the Upper Dolomia Principale continued. Multiple phases of marine cementation allowed to build a reef-like framework and stabilized the bioherm. According to the geometry relationships between the clinostratified breccia slopes, the basinal deposits and the position of the platforms edges, the paleobathimetry of the bioherm and of the intervening basins can be estimated in 200 m and 600 m respectively.
The San Lucano Valley is located in the Western Dolomite southern sector where the Triassic sedim... more The San Lucano Valley is located in the Western Dolomite southern sector where the Triassic sedimentary succession exceed 2000 m in thickness. In the Rio Bordina valley outcrops a sedimentary succession from the Lower Triassic to Upper Ladinian age including the Moena and Livinallongo basinal formations. The high percentage of the coarse grain like turbidite deposits (cal-carenites or doloarenites and sedimentary breccias) may be interpreted with high rate production and exportatiton from the surrounding carbonate platforms and the high subsidence rate of this Dolomite sector. The neighbouring platforms are represented by the Contrin Formation and the Sciliar Formation; the first one has characterized by a tabular feature while the second one shows a plano-convex geometry as a classic bioconstructed carbonate build-up.
This paper analyses the whole of the Rhaetic facies outcropping in Umbria and Eastern Toscany and... more This paper analyses the whole of the Rhaetic facies outcropping in Umbria and Eastern Toscany and traditionally referred to as Toscan nappe and the Umbrian Units. These facies were deposited on a gently stepping sea floor dominated by storms and are referred to as Formazione del Monte Cetona. This unit is subdivisible in a lower marly member and in an upper carbonate member. The lower unit is characterized by asymmetric thickening up cycles, that show an upward enrichment in carbonate from basal marls to pure limestones at the top. Mud-dominated cycles were common in the deeper portion of the basin while grainy cycles were developed in shallower setting. The calcarenites cycles clearly show a coarsening upward evolution from marly and carbonate mud at the base to coarse bioclastic or oolitic calcarenites at the top. This coarsening evolution was mainly produced by an increase in storm-wave reworking, during a shallowing up evolution, but sometimes tide currents were important. Also in the upper carbonate member there are coarsening and shallowing up cycles, but they are less evident because the lack of a marly base and the widespread dolomitization and recrystallization. At the base of the upper member there are sometimes encrusting biostromes with a plane-convex shape. These small build-ups show a cyclic pattern, probably related to bathymetric fluctuations. Tectonic deformations severally affected the base of the Rhaetic and the underlying formations, but the bottom of the Rhaetic succession clearly marked a generalized deepening testified by the deposition of rather deep marine facies over older sabkha evaporites. This deepening episode was followed by a global shallowing upward evolution, towards evolution, towards the medium portion of the upper member. After a smaller re-deepening, the Rhaetic succession ends with shallow water carbonates.
Il Foglio 079 – Bagolino della Carta Geologica d‟Italia a scala 1:50.000
è stato realizzato nell‟... more Il Foglio 079 – Bagolino della Carta Geologica d‟Italia a scala 1:50.000 è stato realizzato nell‟ambito del Progetto CARG (Legge 226/1999), attraverso convenzioni tra il Servizio Geologico d‟Italia, la Regione Lombardia e la Provincia Autonoma di Trento che hanno affidato il Coordinamento Scientifico del Foglio all‟Università degli Studi di Bologna. L‟area del Foglio Bagolino si localizza nel settore meridionale del Gruppo montuoso dell‟Adamello-Presanella, a cavallo tra la Provincia di Trento (ad Est) e la Regione Lombardia (ad Ovest) e più specificamente nel territorio dei Comuni rappresentati in (Fig. 1). La successione presente in questo Foglio inizia con il basamento metamorfico sudalpino, prosegue con le coperture sedimentarie e vulcaniche permo-triassiche fino alle successioni sedimentarie cretacee, intruse dal batolite terziario Adamello- Presanella. Il Foglio Bagolino ricade completamente nel settore mediano della catena alpina, con i principali rilievi montuosi che superano costantemente i 2000 m di altezza. I principali assi vallivi (Val Camonica e Val Giudicarie inferiore) percorsi rispettivamente dal Fiume Oglio e dal Fiume Chiese, sono contraddistinti da un andamento circa NNE-SSO; la Val Caffaro presenta un decorso circa N-S che diviene E-O solo nel suo tratto finale, consentendone l‟immissione nel Fiume Chiese Nel Foglio ricade anche una limitata porzione del bacino del Fiume Mella (il cui tratto iniziale, in analogia a quello terminale del Caffaro, mostra un andamento E-O, con probabile controllo derivante dalla vicina Linea della Val Trompia). Il terriorio è prevalentemente montuoso, con dislivelli che variano da circa 2214 m di quota del Monte Colombine a circa 799 m del fondovalle a O di Collio, con una altezza media pari a 1425 m s.l.m. Le poche aree pianeggianti sono confinate lungo i principali fondovalle, tra cui l‟ampia valle del Chiese immediatamente a N della sua foce nel Lago d‟Idro. Numerosi laghetti di origine glaciale sono annidati nelle teste delle valli; il più esteso di questi è il Lago della Vacca situato a 2357 m di quota. Accanto agli assi vallivi principali, percorsi da strade che garantiscono una agevole viabilità, l‟accesso alle numerosi valli minori è consentito da una discreta trama di strade minori e/o a uso agro-silvo-pastorale. Buona parte del Foglio presenta comunque problematiche logistiche tipiche delle aree montuose: difficoltà di accesso, stagione adatta al rilevamento concentrata nei mesi estivi; inoltre le aree vallive (più facilmente accessibili) sono densamente vegetate, anche a causa di valori di piovosità superiori alla media (Tabella 1). Il rilevamento geologico è stato eseguito alla scala 1:10.000, nel periodo tra la primavera 2000 e il settembre 2008, utilizzando come base topografica le Carte Tecniche della Regione Lombardia e della Provincia Autonoma di Trento. I criteri del rilevamento hanno seguito, come livello minimo dell‟analisi, le linee guida nazionali, adattandosi poi alle necessità ed opportunità poste dai problemi geologici da affrontare. Sono stati raccolti campioni dei diversi litotipi e sono stati misurati gli elementi del fabric visibili in affioramento (superfici primarie, foliazioni, assi di pieghe e piani assiali); sono state inoltre visionate le foto aeree al fine di avere una visione d‟insieme dell‟area di studio, anche se alle quote più basse l‟ampia copertura boschiva permette solo un uso parziale delle stesse; sono comunque state utilizzate per migliorare la realizzazione della carta geologica. Per le unità continentali più recenti, che ammantano il “substrato”, è stato utilizzato invece il criterio allostratigrafico, ridefinendo successivamente le unità come UBSU (Unconformity Bounded Stratigraphic Unit). Il Foglio è stato realizzato sotto il coordinamento scientifico di G IUSEPPE M ARIA B ARGOSSI , e la supervisione dei direttori di rilevamento F ABRIZIO B ERRA , P ETER B RACK , G IAN B ARTOLOMEO S ILETTO (substrato) e di A NDREA B ORSATO e D ANIELE C ORBARI (quaternario). Il rilievo geologico è stato eseguito da S. A LBINI , A. B INI , P. F ERRETTI , D. G AZZOLA , M. G ISOLO , S. R ACCHETTI (settore lombardo) e da E. M ARCATO , S. P ASSAMANI , G.L. T ROMBETTA (settore trentino). Gli studi complementari per la petrologia dei prodotti magmatici sono stati eseguiti da G. G ASPAROTTO e M. M AROCCHI . La stesura delle Note illustrative è stata curata dai seguenti Autori: G.M. B ARGOSSI , F. B ERRA , A. B ORSATO , P. B RACK , D. C ORBARI , G. G ASPAROTTO , E. M ARCATO , M. M AROCCHI , G.B. S ILETTO , G.L. T ROMBETTA con contributi di S. A LBINI , A. B INI , C. F ERLIGA , P. F ERRETTI , L. F RONER D. G AZZOLA , M. G ISOLO , O. G ROAZ , S. P ASSAMANI , S.R ACCHETTI e A. V IGANÒ .
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Papers by G. Trombetta
than other areas of the central-western Dolomites and which corresponds to the Biois and Cordevole torrents Lower Ladinian
Basin, delimited to the north from the Marmolada – Costabella Group, to the east from the Alto di Pelsa (Mt. Civetta Group) and
to the south from the Pale di San Lucano (Pale di San Martino Group). Therefore, an attempt was made to combine the data and
information present in the literature with new observations both on a macroscopic scale (description of carbonate complexes)
and in detail through the analysis and measurement of many basin stratigraphic sections, some already proposed previously.
by the authors and other unpublished ones. In particular, some stratigraphic sections have been revised and an attempt has
been made to quantify the volumes of the re-sedimented deposits in the basin based on their texture, as already done previously
for the stratigraphic succession of Rio Bordina (Trombetta & Masetti, 2012); the next step was to correlate the texture and thickness of the basin deposits with the geometry of the carbonate complexes and with the inclination of the clinoforms within them
in order to review the evolution models of the carbonate platforms surrounding the Biois river basin. The facies analysis conducted on the Livinallongo Formation basin sequences showed that the greatest lateral variability is recorded within the Bänderkalke member, while the lower and middle members – Plattenkalke and Knollenkalke – appear more uniform
quadro paleogeografico di età Carnico inferiore delle Dolomiti Occidentali. Queste piattaforme del Carnico inferiore erano popolate da patchreefs
a coralli e mounds a spugne separati da piccole lagune caratterizzate da sedimentazione fangosa (micrite). Il Settsass/Richthofen Riff è un
piccolo sistema di piattaforma carbonatica (3-4 Km2 di estensione per circa 150 m di spessore) ed è caratterizzato dalla sovrapposizione da due
edifici di piattaforma (DC1 e DC2) che mostrano differente forma geometrica:
a) l’edificio inferiore, conosciuto come Richthofen Riff (DC 1), mostra una geometria piano-convessa il cui nucleo è costituito da patch-reef a
coralli e mound a spugne, mentre le parti laterali sono rappresentate da depositi di scarpata interdigitati con i depositi bacinali (Formazione
di San Cassiano);
b) il complesso carbonatico superiore, cioè il rilievo del Settsass (DC 2), mostra una geometria tabulare e/o che si ispessisce leggermente verso il
bacino (thickening basinward). Questo complesso superiore conserva al suo interno differenti ambienti deposizionali che variano dai depositi
di piattaforma interna (back-reef), del versante sud-occidentale, a quelli di slope registrati lungo il versante sud-orientale del Settsass. I depositi
di slope sono costituiti da brecce clinostratificate con angoli di slope variabili da 20°-25°, nelle aree prossimali, a 10°-15° in quelle distali.
Il complesso di piattaforma del Settsass mostra una progradazione verso il bacino che può essere seguita in affioramento per circa 2 km.
Parole chiave: piattaforme carbonatiche, Dolomia Cassiana, reefs a Coralli, mounds a spugne, clinoformi, progradazione, Triassico, Regione
Dolomitica, Alpi Meridionali.
Abstract
Facies analysis and architecture of a Carnian carbonate platform: the Settsass/Richthofen Riff (Dolomites, Southern Alps, Northern
Italy).
The Settsass/Richthofen Riff carbonate platform system, together with the other central-western Dolomites post-volcanic carbonate complexes,
forms the palaeogeographic scenario of the Lower Carnian age. These Lower Carnian platforms were dwelled by coral patch-reefs and sponge
mounds separated by small lagoons characterized by muddy sedimentation. The Settsass/Richthofen Riff is a small platform system (3-4 km2 in
plain view and about 150 m thick) and is characterized by two superimposed carbonate complexes (DC 1 and DC 2) showing different geometric
features:
a) the lower complex, known as the Richthofen Riff (DC 1), shows a plane-convex geometry where the core is constituted by coral patch-reefs
and sponge bodies, while the lateral portion is represented by the slope sediments interfingering with the basinal deposits (San Cassiano
Formation);
b) the upper complex, the proper Settsass relief (DC 2), shows a tabular geometry and/or some thickening basinward. This upper complex covers
a variety of depositional settings, from inner platform deposits (back-reef ) at the southwestern side, to slope deposits at the southeastern side.
Its slope deposits are formed by clinostratified breccias with slope angles ranging from 20° - 25° in the proximal area, to 10° - 15° more distally.
The Settsass platform complex shows a basinward progradation (NE direction) which can be traced in outcrops for almost 2 km.
Keywords: Carbonate platforms, Cassian Dolomite, Sponges and Coral-reefs, clinoforms, progradation, Triassic, Dolomites Region, Southern Alps
showing the sedimentary cyclicity discussed above (about 140 m), a middle micritic member (300 m) and an upper member exhibiting sedimentary cycles similar to those of the lower member, but finer in texture (about 200 m). In the northern area the sediments “infilling” are coarser because the marginal platform (Dosso delle Saette) keeps exporting carbonate sediments down into the basin until the deposition of the Riva di Solto Shale. On the other hand (Capovalle) the southern marginal platforms drowns earlier than in the northern area and is followed by the basinal sediments of the Zorzino Limestone. This drowning event is shown at Mt. Manos and Mt. Carzen. This palaeo-morphology linked to the extensional phase developed in the Norian, becomes finally “frozen” by the Rhaetian transgressive event, when the deposition of the Riva di Solto Shale capped the sequence and filled the low adjacent areas.
Key words: Norian, Upper Triassic, Carbonate Platforms, Stratigraphy, Paleogeography, Sedimentary Cyclicity, Clinostratified breccias, Megabreccias.
Key words: Stratigraphy, Upper Ladinian, tectonics, normal faults, Western Dolomites
Key words: Stratigraphy, Upper Ladinian, tectonics, normal faults, Western Dolomites
The fossiliferous associations are preserved both within calcareous balck shales (part of the Zorzino Limestone) and in younger laminated claystones (Riva di Solto Shale lower part, “Rhaetic Facies”).
The older fossiliferous associations were preserved during a carbonate depositional phases characterized by emerging areas, large stromatolitic tidal flats, shallow platform lagoons and marginal reefs. The reefs were dominated by algae, serpulid worms and other encrusting organisms and flanked by narrow, poorly oxigenated intraplatform depressions. The fossiliferous beds deposited within these depressions contain mainly nectonic crustaceans and bony fishes. The majority of these faunae adapted to reef environment, but lagoon and terrestrial organisms are also included. Vertebrate associations show some of the most ancient known flying reptiles. The ecological compositionof the continental vertebrate faunas was probably similar to that of modern tropical keys.
than other areas of the central-western Dolomites and which corresponds to the Biois and Cordevole torrents Lower Ladinian
Basin, delimited to the north from the Marmolada – Costabella Group, to the east from the Alto di Pelsa (Mt. Civetta Group) and
to the south from the Pale di San Lucano (Pale di San Martino Group). Therefore, an attempt was made to combine the data and
information present in the literature with new observations both on a macroscopic scale (description of carbonate complexes)
and in detail through the analysis and measurement of many basin stratigraphic sections, some already proposed previously.
by the authors and other unpublished ones. In particular, some stratigraphic sections have been revised and an attempt has
been made to quantify the volumes of the re-sedimented deposits in the basin based on their texture, as already done previously
for the stratigraphic succession of Rio Bordina (Trombetta & Masetti, 2012); the next step was to correlate the texture and thickness of the basin deposits with the geometry of the carbonate complexes and with the inclination of the clinoforms within them
in order to review the evolution models of the carbonate platforms surrounding the Biois river basin. The facies analysis conducted on the Livinallongo Formation basin sequences showed that the greatest lateral variability is recorded within the Bänderkalke member, while the lower and middle members – Plattenkalke and Knollenkalke – appear more uniform
quadro paleogeografico di età Carnico inferiore delle Dolomiti Occidentali. Queste piattaforme del Carnico inferiore erano popolate da patchreefs
a coralli e mounds a spugne separati da piccole lagune caratterizzate da sedimentazione fangosa (micrite). Il Settsass/Richthofen Riff è un
piccolo sistema di piattaforma carbonatica (3-4 Km2 di estensione per circa 150 m di spessore) ed è caratterizzato dalla sovrapposizione da due
edifici di piattaforma (DC1 e DC2) che mostrano differente forma geometrica:
a) l’edificio inferiore, conosciuto come Richthofen Riff (DC 1), mostra una geometria piano-convessa il cui nucleo è costituito da patch-reef a
coralli e mound a spugne, mentre le parti laterali sono rappresentate da depositi di scarpata interdigitati con i depositi bacinali (Formazione
di San Cassiano);
b) il complesso carbonatico superiore, cioè il rilievo del Settsass (DC 2), mostra una geometria tabulare e/o che si ispessisce leggermente verso il
bacino (thickening basinward). Questo complesso superiore conserva al suo interno differenti ambienti deposizionali che variano dai depositi
di piattaforma interna (back-reef), del versante sud-occidentale, a quelli di slope registrati lungo il versante sud-orientale del Settsass. I depositi
di slope sono costituiti da brecce clinostratificate con angoli di slope variabili da 20°-25°, nelle aree prossimali, a 10°-15° in quelle distali.
Il complesso di piattaforma del Settsass mostra una progradazione verso il bacino che può essere seguita in affioramento per circa 2 km.
Parole chiave: piattaforme carbonatiche, Dolomia Cassiana, reefs a Coralli, mounds a spugne, clinoformi, progradazione, Triassico, Regione
Dolomitica, Alpi Meridionali.
Abstract
Facies analysis and architecture of a Carnian carbonate platform: the Settsass/Richthofen Riff (Dolomites, Southern Alps, Northern
Italy).
The Settsass/Richthofen Riff carbonate platform system, together with the other central-western Dolomites post-volcanic carbonate complexes,
forms the palaeogeographic scenario of the Lower Carnian age. These Lower Carnian platforms were dwelled by coral patch-reefs and sponge
mounds separated by small lagoons characterized by muddy sedimentation. The Settsass/Richthofen Riff is a small platform system (3-4 km2 in
plain view and about 150 m thick) and is characterized by two superimposed carbonate complexes (DC 1 and DC 2) showing different geometric
features:
a) the lower complex, known as the Richthofen Riff (DC 1), shows a plane-convex geometry where the core is constituted by coral patch-reefs
and sponge bodies, while the lateral portion is represented by the slope sediments interfingering with the basinal deposits (San Cassiano
Formation);
b) the upper complex, the proper Settsass relief (DC 2), shows a tabular geometry and/or some thickening basinward. This upper complex covers
a variety of depositional settings, from inner platform deposits (back-reef ) at the southwestern side, to slope deposits at the southeastern side.
Its slope deposits are formed by clinostratified breccias with slope angles ranging from 20° - 25° in the proximal area, to 10° - 15° more distally.
The Settsass platform complex shows a basinward progradation (NE direction) which can be traced in outcrops for almost 2 km.
Keywords: Carbonate platforms, Cassian Dolomite, Sponges and Coral-reefs, clinoforms, progradation, Triassic, Dolomites Region, Southern Alps
showing the sedimentary cyclicity discussed above (about 140 m), a middle micritic member (300 m) and an upper member exhibiting sedimentary cycles similar to those of the lower member, but finer in texture (about 200 m). In the northern area the sediments “infilling” are coarser because the marginal platform (Dosso delle Saette) keeps exporting carbonate sediments down into the basin until the deposition of the Riva di Solto Shale. On the other hand (Capovalle) the southern marginal platforms drowns earlier than in the northern area and is followed by the basinal sediments of the Zorzino Limestone. This drowning event is shown at Mt. Manos and Mt. Carzen. This palaeo-morphology linked to the extensional phase developed in the Norian, becomes finally “frozen” by the Rhaetian transgressive event, when the deposition of the Riva di Solto Shale capped the sequence and filled the low adjacent areas.
Key words: Norian, Upper Triassic, Carbonate Platforms, Stratigraphy, Paleogeography, Sedimentary Cyclicity, Clinostratified breccias, Megabreccias.
Key words: Stratigraphy, Upper Ladinian, tectonics, normal faults, Western Dolomites
Key words: Stratigraphy, Upper Ladinian, tectonics, normal faults, Western Dolomites
The fossiliferous associations are preserved both within calcareous balck shales (part of the Zorzino Limestone) and in younger laminated claystones (Riva di Solto Shale lower part, “Rhaetic Facies”).
The older fossiliferous associations were preserved during a carbonate depositional phases characterized by emerging areas, large stromatolitic tidal flats, shallow platform lagoons and marginal reefs. The reefs were dominated by algae, serpulid worms and other encrusting organisms and flanked by narrow, poorly oxigenated intraplatform depressions. The fossiliferous beds deposited within these depressions contain mainly nectonic crustaceans and bony fishes. The majority of these faunae adapted to reef environment, but lagoon and terrestrial organisms are also included. Vertebrate associations show some of the most ancient known flying reptiles. The ecological compositionof the continental vertebrate faunas was probably similar to that of modern tropical keys.
è stato realizzato nell‟ambito del Progetto CARG (Legge 226/1999),
attraverso convenzioni tra il Servizio Geologico d‟Italia, la Regione
Lombardia e la Provincia Autonoma di Trento che hanno affidato il
Coordinamento Scientifico del Foglio all‟Università degli Studi di Bologna.
L‟area del Foglio Bagolino si localizza nel settore meridionale del
Gruppo montuoso dell‟Adamello-Presanella, a cavallo tra la Provincia di
Trento (ad Est) e la Regione Lombardia (ad Ovest) e più specificamente nel territorio dei Comuni rappresentati in (Fig. 1). La successione presente in questo Foglio inizia con il basamento metamorfico sudalpino, prosegue con
le coperture sedimentarie e vulcaniche permo-triassiche fino alle
successioni sedimentarie cretacee, intruse dal batolite terziario Adamello-
Presanella.
Il Foglio Bagolino ricade completamente nel settore mediano della
catena alpina, con i principali rilievi montuosi che superano costantemente i 2000 m di altezza.
I principali assi vallivi (Val Camonica e Val Giudicarie inferiore)
percorsi rispettivamente dal Fiume Oglio e dal Fiume Chiese, sono
contraddistinti da un andamento circa NNE-SSO; la Val Caffaro presenta un decorso circa N-S che diviene E-O solo nel suo tratto finale, consentendone l‟immissione nel Fiume Chiese Nel Foglio ricade anche una limitata porzione del bacino del Fiume
Mella (il cui tratto iniziale, in analogia a quello terminale del Caffaro,
mostra un andamento E-O, con probabile controllo derivante dalla vicina
Linea della Val Trompia).
Il terriorio è prevalentemente montuoso, con dislivelli che variano da
circa 2214 m di quota del Monte Colombine a circa 799 m del fondovalle a
O di Collio, con una altezza media pari a 1425 m s.l.m. Le poche aree
pianeggianti sono confinate lungo i principali fondovalle, tra cui l‟ampia
valle del Chiese immediatamente a N della sua foce nel Lago d‟Idro.
Numerosi laghetti di origine glaciale sono annidati nelle teste delle valli; il
più esteso di questi è il Lago della Vacca situato a 2357 m di quota.
Accanto agli assi vallivi principali, percorsi da strade che garantiscono
una agevole viabilità, l‟accesso alle numerosi valli minori è consentito da
una discreta trama di strade minori e/o a uso agro-silvo-pastorale. Buona
parte del Foglio presenta comunque problematiche logistiche tipiche delle
aree montuose: difficoltà di accesso, stagione adatta al rilevamento concentrata nei mesi estivi; inoltre le aree vallive (più facilmente
accessibili) sono densamente vegetate, anche a causa di valori di piovosità superiori alla media (Tabella 1).
Il rilevamento geologico è stato eseguito alla scala 1:10.000, nel periodo
tra la primavera 2000 e il settembre 2008, utilizzando come base
topografica le Carte Tecniche della Regione Lombardia e della Provincia
Autonoma di Trento. I criteri del rilevamento hanno seguito, come livello
minimo dell‟analisi, le linee guida nazionali, adattandosi poi alle necessità
ed opportunità poste dai problemi geologici da affrontare.
Sono stati raccolti campioni dei diversi litotipi e sono stati misurati gli
elementi del fabric visibili in affioramento (superfici primarie, foliazioni,
assi di pieghe e piani assiali); sono state inoltre visionate le foto aeree al
fine di avere una visione d‟insieme dell‟area di studio, anche se alle quote
più basse l‟ampia copertura boschiva permette solo un uso parziale delle
stesse; sono comunque state utilizzate per migliorare la realizzazione della
carta geologica.
Per le unità continentali più recenti, che ammantano il “substrato”, è
stato utilizzato invece il criterio allostratigrafico, ridefinendo
successivamente le unità come UBSU (Unconformity Bounded
Stratigraphic Unit).
Il Foglio è stato realizzato sotto il coordinamento scientifico di
G IUSEPPE M ARIA B ARGOSSI , e la supervisione dei direttori di rilevamento
F ABRIZIO B ERRA , P ETER B RACK , G IAN B ARTOLOMEO S ILETTO (substrato) e
di A NDREA B ORSATO e D ANIELE C ORBARI (quaternario).
Il rilievo geologico è stato eseguito da S. A LBINI , A. B INI , P. F ERRETTI ,
D. G AZZOLA , M. G ISOLO , S. R ACCHETTI (settore lombardo) e da E.
M ARCATO , S. P ASSAMANI , G.L. T ROMBETTA (settore trentino).
Gli studi complementari per la petrologia dei prodotti magmatici sono
stati eseguiti da G. G ASPAROTTO e M. M AROCCHI .
La stesura delle Note illustrative è stata curata dai seguenti Autori:
G.M. B ARGOSSI , F. B ERRA , A. B ORSATO , P. B RACK , D. C ORBARI , G.
G ASPAROTTO , E. M ARCATO , M. M AROCCHI , G.B. S ILETTO , G.L.
T ROMBETTA con contributi di S. A LBINI , A. B INI , C. F ERLIGA , P.
F ERRETTI , L. F RONER D. G AZZOLA , M. G ISOLO , O. G ROAZ , S.
P ASSAMANI , S.R ACCHETTI e A. V IGANÒ .