1,721,098 research outputs found
Characters and significance of the coarse-chaotic deposits within the deep-sea turbidite systems of the Northern Apennines (Oligocene-Miocene, Macigno Fm.)
No full textSedimentary evolution of a migrating thrust-belt-foredeep system: Physical stratigraphy and sedimentology of the Macigno Fm. of Southern Tuscany (Northern Apennines) [Evoluzione deposizionale di un settore del sistema catena-avanfossa dell'Appennino settentrionale: stratigrafia fisica e sedimentologia del Macigno della Toscana meridionale]
No full textThe Macigno deep-sea turbidite unit was part of the diachronically migrating foredeep system characterizing the collisional phases of the apenninic orogen at the transition between Oligocene and Miocene time. The Macigno Fm. stratigraphically rests above the Scaglia toscana, a pelitic and calcareous unit of basin plain environment, while it is superimposed by the ligurian and subligurian thrust sheets that formed the accretionary prism in the internal margin of the foredeep. The nappe was responsible, with its advancing, of the migration of the depocenter basin and of the progressive reduction and closure of the sedimentation. The turbidite deposition gradually moved from the inner Tuscan domain (Macigno clastic wedge) to the outer Tuscan domain (Cervarola-Falterona clastic wedge), and from here to the outermost Umbro-Marchean domain (Marnoso-arenacea clastic wedge), as fully explained in several papers. Here I have studied the lesser known southern Macigno outcrops of the southern Tuscany, along a transversal chain transect from the inner outcrops of the Piombino-Baratti area to west, to the outer outcrops of the Chianti region to east, through the outcrops of the Sassetta area in the inland Marittime Tuscany, and of the Poggio Ritrovoli area in the Colline Metallifere region. The aim is to contribute for a better knowledge of the depositional evolution of the Northern Apennines foredeep system. The methods of research have been a detailed 1:10.000 geological mapping and stratigraphical-sedimentological analyses aimed at reconstruction of the architecture of the depositional systems. The geological mapping has allowed to recognize the relationships between Macigno and others formations, and to define the tectonic units stack. The vertical distribution of nine sedimentological facies (of genetic type) has allowed defining five facies associations indicative of specific turbidite environments. The facies analysis shows for the innermost Baratti succession, multiple stages of progradingaggrading lobe system moved until to a channel proximal to the slope stage that is previous to the closure of the basin through the allochtonous ligurian thrust sheet. Eastward, in the outer succession of Sassetta, the turbidite system is characterised by progradingaggrading lobe system in turn replaced by starved basin deposits in the upper part. Olistostromes coming from the internal slope are embedded in the top part. The allochthonous thrust sheet closed the depositional system. Eastward again, the Poggio Ritrovoli succession has got the same features of the previous, with lesser evident thickening and coarsening upward trends for the middle part, and with peculiar presence of several carbonaceous turbidite bedsets interlayered to the siliciclastic deposits. Also in this succession, the normal-feeding turbidite system is superimposed by a thick interval of starved basin deposits topped by several olistostromes coming from the advancing nappe, and then closing it. The outermost succession, located in the southern sector of the Chianti region, has shown very developed facies and facies associations typical of distal lobe environment; carbonaceous turbidite beds are also recognized. The whole data suggest a complicated framework of the foredeep turbidite system at the Oligo-Miocene transition. Two main types of turbidite systems belonging to the same foredeep system have been distinguished. The internal and oldest succession of Macigno costiero reveals turbidite proximal conditions, and typical features of low-efficiency turbidite system, with feeding transversal to the basin coming from storage basins close to the Corso-Sardinian Massif. To follow the foredeep depositional system migrated toward outer position with changes in the turbidite fed, longitudinal to the basin, from farther source like western alpine crystalline terrain. The turbidite system changed to high-efficiency, migrating on space and on time, with progressively deactivation of the sedimentation, due to the approaching of the allochtonous thrust sheet, as showed by replacing of starved sediments and olisthostromes onto lobe turbidite sedimentation. In conclusion, the research has allowed to identify two turbidites system for the Macigno in Northern Apennines, the oldest and innermost, of low-efficiency type, transversal to the foredeep structural chain system deposited in open piggyback or inner complex foredeep basin, and the other, younger and wider long-lived migrating high-efficiency turbidite system deposited in wide foredeep basins
Sand-rich turbidite system of the Late Oligocene Northern Apennines foredeep: physical stratigraphy and architecture of the "Macigno costiero" (coastal Tuscany, Italy
No full textThe 'Macigno costiero' turbidite system characterized the oldest foredeep elastic wedge of the Northern Apennines during the Late Oligocene collisional phase. The cropping-out thickness is about 500 m. The features of the 'Macigno costiero' indicate a sand-rich, low-efficiency turbidite system. The system developed within a partially confined basin, which was part of a complex foredeep system. The stacking pattern of the turbidite system was determined through the analysis of facies and physical stratigraphy. It consists of a succession organized in sedimentary units, which are characterized by particular associations of facies linked to distinct depositional environments. Several architectural elements are seen: (1) unchannelized and channelized lobes; (2) distributary channels with channel-fill, overbank and channel-margin deposits; (3) main channel with channel-fill, channel-margin and interchannel deposits. Five turbidite stages were identified. From the bottom up they consist of four lobe stages and one proximal channel stage. The lobe stages are characterized by thickening-coarsening upward trends, from distal lobes to proximal lobes up to the channel-lobe transition zone. The uppermost, fifth stage is linked to a main channel complex with stacked channel-fill, channel-margin and interchannel deposits. This final stage also marks the maximum progradation of the system up to its closure due to the synsedimentary overthrusting of the orogenic wedge
Sedimentation in the Northern Apennines-Corsica tectonic knot (Northern Tyrrhenian Sea, Central Mediterranean): offshore drilling data from the Elba-Pianosa Ridge
No full textThe Northern Tyrrhenian Sea is located on the collisional zone between the Alpine Corsica and the Northern Apennines and is a key area for gaining a better understanding of the complex relationships between these two systems. The knowledge of the wide offshore part of this zone, located between Corsica (France) and mainland Italy, is based primarily on the analysis of several seismic profiles tied to the outcropping geology and unpublished preliminary reports of few offshore wells. The here presented study of two offshore wells provides a revision of the sedimentology, biostratigraphy and petrography of the thick, mainly siliciclastic, Tertiary successions (about 3,600 m) composing the Elba-Pianosa Ridge (EPR), a structural/morphological high separating the Tuscan Shelf to the east from the Corsica Basin to the west. A comparison with similar deposits cropping out in the surrounding onshore areas (Northern Apennines, Corsica, Tuscan Archipelago, Piedmont Tertiary Basin) provides additional constraints for refinement of the complex geodynamic and regional setting in which the EPR evolved. © 2014 Springer-Verlag Berlin Heidelberg
Provenance, depositional and palaeogeographic insights from the coarse-disorganised deposits of the Macigno turbidite systems (late Oligocene-early Miocene, Northern Apennines)
No full text
Geological setting of the Bagno Vignoni area (northern side of the Mt. Amiata geothermal area, Italy): collisional structures recorded in the Tuscan Nappe
No full textGeological studies carried out in the Bagno Vignoni area (southern Tuscany) for the realisation of the new Geological Map of Tuscany (1:10,000 scale), and the interpretation of the Cro.P.18 crustal seismic line, highlighted new structural data for the Tuscan Nappe occurring on the northern side of the Mt. Amiata geothermal area. The Tuscan Nappe was affected by polyphase tectonics, as documented by structural data mainly detected from map-scale and microstructural analyses. The Tuscan Nappe in the Bagno Vignoni area consists of small outcrops emerging from Ligurian l.s. Units, mainly composed of the <> Unit. The Tuscan Nappe is typified by repetitions of its stratigraphical succession due to the presence of imbricate thrusts. They are associated with a collisional, southeast-verging thrust system which produced three Tuscan Nappe subunits, highlighted by field mapping and borehole stratigraphy. The lowermost outcropping subunit (SU3) is composed of the stratigraphical succession ranging from the <>. Fm. to the <> Fm.; the overlying SU2 is characterised only by the <> and <> Fms., whereas the uppermost SU1 is composed of the <> Fm. and the <> Fm. The Tuscan Nappe subunits stack was later deformed by Early-Middle Miocene low-angle normal faults which produced widespread tectonic elision between the thickened Tuscan Nappe and Ligurian Units. In fact, in the study area, the <> Unit, mainly composed of <> and <> Fms., lies on different Tuscan Nappe formations, suggesting the tectonic elision of the uppermost Tuscan Nappe formations, of the Subligurian Unit and of the lowermost formations of the <> Unit. On the whole, Tuscan Nappe collisional structures occur-ring in the Bagno Vignoni area represent relict structures preserved during extensional tectonics. The evidence also demonstrates the occurrence of collisional structures in the northern part of the Mt. Amiata geothermal area, as well as in the western and eastern sides (Mt. Aquilaia-Mt. Buceto and Poggio Zoccolino-Campiglia d'Orcia)
The Corsica-Sardinia Massif as source area for the early northern Apennines foredeep system: evidence from debris flows in the “Macigno costiero” (Late Oligocene, Italy)
No full textLarge isolated gravity flows (debrites) are widely present in the stratigraphic record of the northern Apennines foreland-basin system. These strata may be useful for provenance signals and dispersal pathways during foreland evolution. This paper examines a cohesive debris flow bed interbedded with turbidite strata of the Macigno Formation (Late Oligocene, Tuscany, Italy), in order to obtain new data on the provenance of the elastic material. Clasts in the debris flow are predominantly plutonic (granodiorite, tonalite, and S-granite) and subordinately metamorphic (gneiss and schist) and sedimentary calcareous clasts. The composition of the clasts within the debris flow is similar to the clastic composition of the interbedded turbidite sandstones of the "Macigno costiero." The depositional features of the debris flow suggest that it traveled for a short distance within the basin before it was deposited not far from the slope. The absence of a high-pressure/low-temperature (HP/LT) paragenesis in the plutonic and metamorphic clasts of the debris flow indicates a provenance from a crystalline basement not involved in the high-pressure phases of the Alpine Orogenesis. Previous studies have indicated the Central-Western Alps as potential source areas for the Macigno Formation sediments. The lack of HP/LT tuetamorphic signatures in our studied samples excludes the Pennidic aud Austroalpine nappes of the Western Alps as possible sources for the debris flows of the "Macigno costiero." These new data (sedimentological, petrographical, and microstructural) suggest that the Corsica-Sardinia Hercynian basement, lacking a HP/LT paragenesis, is the more accredited source area of the debris flow and of the related turbidite sandstones of the "Macigno costiero" succession. These foredeep-feeding sediments were probably before deposited within an episutural basin developed close to the northern Apennines orogenic wedge
- …
