102,002 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 textSistemi torbiditici interagenti nell'avanfossa oligocenica nordappenninica: dati petrografico-stratigrafici del Macigno della Toscana meridionale costiera
No full textGuide Geologiche Regionali Toscana
No full textLa Guida Geologica Regionale n. 15 della Toscana giunge nella disponibilità dei soci della Società Geologica Italiana come quinta opera della nuova serie, esattamente a distanza di 20 anni dalla precedente Guida Geologica Regionale dell’Appennino Tosco-Emiliano a cura di V. Bortolotti.
La Società Geologica Italiana pubblica le Guide Geologiche Regionali dal 1990, la nuova serie, di cui la Guida della Toscana fa parte, è iniziata nel 2016 e sta proseguendo con cadenza annuale. Con questa nuova opera delle Guide Geologiche Regionali, la Società Geologica Italiana prosegue l’azione d’informazione-divulgazione dei paesaggi geologici e dei principali processi che modellano il nostro territorio determinandone la sua bellezza, ma anche le sue vulnerabilità e i rischi naturali.
La conoscenza del territorio e le sue peculiarità sono la base essenziale per una sensibilizzazione e un coinvolgimento dell’opinione pubblica e delle amministrazioni locali per la valorizzazione della risorsa paesaggistica/geologica e per comprendere equilibri/disequilibri dell’ambiente e delle sue fragilità.
La Guida rappresenta un prodotto di divulgazione delle “Scienze della Terra” che dove è possibile ha cercato di valorizzare le peculiarità geologiche/paesaggistiche e del patrimonio geo-minerario come Musei, Parchi e aree Naturali Protette presenti sul territorio, anche attraverso una paziente e rigorosa opera di coordinamento fra mondo accademico e della ricerca con le realtà locali.
La Guida Geologica della Toscana contiene una parte introduttiva con 10 capitoli dedicati alle caratteristiche geologiche, alle Risorse Geologiche e i Parchi Naturali e Musei di Geologia e Scienze Naturali del territorio considerato. La Guida propone 12 itinerari a carattere regionale e/o tematico che comprendono sia la parte continentale che le isole dell’Arcipelago Toscano. L’opera si rivolge non soltanto ai geologi (o aspiranti geologi) e ai naturalisti, ma anche agli escursionisti e agli appassionati del paesaggio, che difficilmente trovano in un solo volume notizie delle caratteristiche geologiche del territorio e delle sue attività museali. Le difficoltà per i non esperti in geologia potranno essere superate con la lettura preventiva dei primi 10 capitoli della parte generale e con l’aiuto del glossario presente alla fine del volume.
L’opera è contraddistinta da una notevole cura della parte fotografica e iconografica con carte, schizzi e schemi molto ben curati e di aiuto nella lettura e comprensione degli affioramenti e dei paesaggi descritti.
Gli Itinerari proposti variano in lunghezza e difficoltà da semplici itinerari da fare in automobile o passeggiate su facili sentieri, a salite più impegnative per dislivello, quota ed orientamento. La selezione dei percorsi proposti è fatta nell’intento di soddisfare sia i geologi che gli escursionisti cercando di fornire una visione ampia delle diversità del territorio e delle sue peculiarità.
La Società Geologica Italiana è profondamente grata ai curatori della Guida P. Conti, S. Conticelli, G. Cornamusini e M. Marroni per aver diretto con competenza, passione e determinazione la realizzazione di questo volume e ai ben quasi 90 co-autori. La stretta collaborazione ha permesso la stesura e la descrizione dei capitoli tematici e degli itinerari, nonostante le limitazioni dovute all’emergenza sanitaria per il contrasto della pandemia da SARS-CoV-2
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