1,358,348 research outputs found
Late Precambrian U-Pb titanite age for peak regional metamorphism and deformation (Knoydartian orogeny) in the western Moine, Scotland
No full textThere has been controversy over the number and timing of orogenies in the Precambrian Moine block in the Scottish Caledonides since the earliest radiometric dating in the 1960s. This work challenges a recent hypothesis, that this sector of the Laurentian margin was subjected to continuous crustal extension between greater than 900 and 470 Ma. U-Pb dating (thermal ionization mass spectrometry) of titanite from a calcsilicate pod in the Moine (Morar Group) of the western Highlands gives an age of 737 ñ 5 Ma. The titanite grew from Fe-Ti-bearing detrital minerals during the main progressive, syn-D2, amphibolite-facies (sillimanite zone) regional metamorphism, thus demonstrating that a Neoproterozoic contractional tectonothermal event (Knoydartian orogeny) affected the Moine block following the rift-related emplacement of the West Highland granite gneiss at 873 Ma. We conclude that the Sgurr Beag Thrust, a major tectonic break separating the Morar and Glenfinnan groups of the Moine, is mainly of Neoproterozoic, not Caledonian, age. The early tectonothermal event was succeeded by the Grampian Phase (Caledonian orogeny) at 460-470 Ma
Neoproterozoic to early Paleozoic extensional and compressional history of East Laurentian margin sequences:the Moine Supergroup, Scottish Caledonides
No full textThis work was in part supported by Natural Environment Research Council grant NE/J021822/1, National Science Foundation grant EAR-0087650, and funds from our respective institutions.Neoproterozoic siliciclastic-dominated sequences are widespread along the eastern margin of Laurentia and are related to rifting associated with the breakout of Laurentia from the supercontinent Rodinia. Detrital zircons from the Moine Supergroup, NW Scotland, yield Archean to early Neoproterozoic U-Pb ages, consistent with derivation from the Grenville-Sveconorwegian orogen and environs and accumulation post–1000 Ma. U-Pb zircon ages for felsic and associated mafic intrusions confirm a widespread pulse of extension-related magmatism at around 870 Ma. Pegmatites yielding U-Pb zircon ages between 830 Ma and 745 Ma constrain a series of deformation and metamorphic pulses related to Knoydartian orogenesis of the host Moine rocks. Additional U-Pb zircon and monazite data, and 40Ar/39Ar ages for pegmatites and host gneisses indicate high-grade metamorphic events at ca. 458–446 Ma and ca. 426 Ma during the Caledonian orogenic cycle.The presence of early Neoproterozoic siliciclastic sedimentation and deformation in the Moine and equivalent successions around the North Atlantic and their absence along strike in eastern North America reflect contrasting Laurentian paleogeography during the breakup of Rodinia. The North Atlantic realm occupied an external location on the margin of Laurentia, and this region acted as a locus for accumulation of detritus (Moine Supergroup and equivalents) derived from the Grenville-Sveconorwegian orogenic welt, which developed as a consequence of collisional assembly of Rodinia. Neoproterozoic orogenic activity corresponds with the inferred development of convergent plate-margin activity along the periphery of the supercontinent. In contrast in eastern North America, which lay within the internal parts of Rodinia, sedimentation did not commence until the mid-Neoproterozoic (ca. 760 Ma) during initial stages of supercontinent fragmentation. In the North Atlantic region, this time frame corresponds to a second pulse of extension represented by units such as the Dalradian Supergroup, which unconformably overlies the predeformed Moine succession.Peer reviewe
U-Pn geochronology of deformed metagranites in central Sutherland, Scotland: evidence for widespread late Silurian metamorphism and ductile deformation of the Moine Supergroup during the Caledonian orogeny
No full textWithin the Caledonides of central Sutherland, Scotland, the Neoproterozoic metasedimentary rocks of the Moine Supergroup record NW-directed D2 ductile thrusting and nappe assembly, accompanied by widespread tight-to-isoclinal folding and amphibolite-facies metamorphism. A series of metagranite sheets which were emplaced and penetratively deformed during D2 have been dated using SHRIMP UâPb geochronology. Zircon ages of 424 8 Ma (Vagastie Bridge granite), 420 6 Ma (Klibreck granite) and 429 11 Ma (Strathnaver granite) are interpreted to date emplacement, and hence regional D2 deformation, during
mid- to late Silurian time. Titanite ages of 413 3 Ma (Vagastie Bridge granite) and 416 3 Ma (Klibreck granite) are thought to date post-metamorphic cooling through a blocking temperature of c. 550â 500 8C. A mid- to late Silurian age for D2 deformation supports published models that have viewed the internal ductile thrusts of this part of the orogen as part of the same kinematically linked system of forelandpropagating thrusts as the marginal Moine Thrust Zone. The new data contrast with previous interpretations that have viewed the dominant structures and metamorphic assemblages within the Moine Supergroup as having formed during the early to mid-Ordovician Grampian arcâcontinent orogeny. The mid-to late Silurian D2 nappe stacking event in Sutherland is probably a result of the collision of Baltica with the Scottish segment of Laurentia
L’isola di domani. Cultura materiale e contesti archeologici a San Giacomo in Paludo (Venezia)
No full textIl libro è la storia dell’isola di ieri e soprattutto della relazione tra i suoi spazi, i suoi abitanti, gli edifici che hanno occupato ed i loro oggetti quotidiani, dal basso medioevo ad oggi.
San Giacomo in Paludo è un’isola della laguna nord di Venezia, oggi disabitata, ma che a partire dal XIII secolo ha ospitato prima una comunità di monache cistercensi, poi un priorato francescano ed infine alcuni presidi militari.
La prima parte del libro racconta le ricerche archeologiche e storiche: la descrizione generale degli spazi occupati e delle singole aree scavate è seguita dalla discussione su specifiche tipologie di dati quali ceramica, resti umani, fauna e fonti storiche.
La seconda parte del lavoro cerca di comprendere il significato di questo luogo nel corso dei diversi momenti storici attraverso il punto di vista degli abitanti e quello di più ampio respiro della laguna.
Il tema principale della ricerca sono le comunità che vi hanno abitato e i loro resti materiali. Le tre principali variabili utilizzate per la loro carattterizzazione sono state l’uso dello spazio, le relazioni con l’area esterna all’isola e, infine, il trattamento dei rifiuti.
In passato il sito è sempre stato uno specchio del rapporto tra Venezia e la sua laguna. Quale sarà l’isola di domani?
Sommario
Ieri, oggi, domani. Storie di un’isola e delle sue genti, di Sauro Gelichi
1. Introduzione, di Margherita Ferri, Cecilia Moine
2. La sequenza insediativa, di Margherita Ferri, Cecilia Moine
3. Tecnologie edilizie, di Fulvio Baudo
4. UTS 1000, di Margherita Ferri, Cecilia Moine
5. UTS 4000, di Carlo Beltrame, Margherita Ferri, Cecilia Moine
6. UTS 3000, di Fulvio Baudo, Margherita Ferri, Cecilia Moine
7. UTS 2000, di Margherita Ferri, Cecilia Moine
8. La sequenza della UTS 7000, di Margherita Ferri
9. La ceramica, di Margherita Ferri, Alberto García Porras, Laura Martín Ramos
10. Ossa animali di mammiferi e di uccelli dal monastero e dal priorato, di Aleks Pluskowski, Kris Seetah, Silvia Garavello
11. Le sepolture di San Giacomo in Paludo, di Francesca Bertoldi, Carlotta Sisalli
12. Le monete rinvenute nello scavo di San Giacomo in Paludo, di Michele Chimienti
13. L’Isola attraverso le fonti scritte, di Cecilia Moine, Elisa Corrò
14. Anima di un’isola, di Margherita Ferri, Cecilia Moine
15. L’isola di domani, di Margherita Ferri, Cecilia Moine
Bibliografia
Summar
U-Pb geochronology of the Fort Augustus granite gneiss: constraints on the timing of Neoproterozoic and Palaeozoic tectonothermal events in the NW Highlands of Scotland
No full textThe West Highland granite gneiss suite in Inverness-shire, Scotland, represents a series of S-type, anatectic granites formed by partial melting of host Neoproterozoic metasediments of the Moine Supergroup. U-Pb (SHRIMP) dating of zircons from a member of the suite, the Fort Augustus granite gneiss, indicates that the granitic protolith to the gneiss was intruded at 870 +/- 30 Ma. This is indistinguishable from the published age determined by the same method for the Ardgour granite gneiss at Glenfinnan, thus supporting the assumption that the various members of the West Highland granite gneiss are part of a single intrusive suite. The spread of ages from the zircon cores (1626-947 Ma) is interpreted to indicate a Proterozoic source terrain for the Moine sediments that were later melted to form the granitic protolith. A U-Pb age of 470+/-2 Ma obtained for titanite in the Fort Augustus granite gneiss is interpreted to date amphibolite-facies metamorphism during the early to mid-Ordovician Grampian Orogeny, The emerging similarity in the timing of this event either side of the Great Glen Fault implies that this structure does not juxtapose crustal blocks with significantly different histories with respect to the Grampian Orogeny
The internal structure of the Moine Nappe Complex and the stratigraphy of the Morar Group in the Fannichs – Beinn Dearg area, NW Highlands
No full textThe Morar Group, the lowest group of the early Neoproterozoic Moine Supergroup in the Scottish Highlands, forms a >5 km thick metamorphosed siliclastic sequence, recently interpreted to form part of a Grenvillian (c. 1000 Ma) foreland basin. New mapping has elucidated the structure and stratigraphy of the Morar Group in the Fannich – Beinn Dearg area, where the Morar Group occurs in a single coherent thrust sheet (Achness Thrust Sheet), over 70 km long, 20 km wide, and up to 10 km thick. Within this thrust sheet, the strata are folded by two very large, west-vergent and west-facing cylindroidal anticline-syncline pairs that deform the overlying Sgurr Beag Thrust. The lowest long limb is parallel with and grades into the ductile Moine Thrust and Achness Thrust at its base. Low strain zones in steep limbs contain well preserved sedimentary structures. Reconstruction of the stratigraphical architecture shows five formations of metasandstone (psammite), alternating with meta-siltstone (semipelite). Large-scale lateral variations in the lowest metasandstone package are capped by a possible flooding surface of semipelite, followed by more metasandstone. The deformation history shows foreland-propagation of both deformation and metamorphism, from NNW-directed transport on the Sgurr Beag Thrust to WNW-directed transport on the Achness Thrust and Moine Thrust
Thrust sheet evolution in the Kinlochewe region of the Moine Thrust Zone, N.W. Scotland and the Pelvoux-Brianconnais, French Alps
No full textBalanced and restored cross sections demonstrate a
minimum 16 km shortening below the Moine Thrust and
minimum restored wi1ths of 17 km between the La Meije and
Combeynot Thrusts (external Alps), and 54 km between the
frontal Subbrianconnais Thrust and the western Brianconnais
Zone (internal Alps). Imbricate thrusts within the Moine
Thrust Zone branch off a floor thrust which cuts up
stratigraphic section from basement (Lewisian gneiss) to
Cambrian shelf sediments parallel to the ESE-WNW movement
direction. Cut-off relationships and fold geometries
within the Pelvoux-Brianconnais suggest a change in move-ment direction of thrust sheets during the evolution of the
French Alps from ENE-WSW for the Brianconnais and Sub-brianconnais Zones to ESE-WNW for the External Zones.
Higher thrust sheets are frequently flexured as a
result of slip on lower thrust surfaces (in-sequence
thrusting). Important examples occur of Imver thrust
assemblages which are truncated by higher thrust surfaces
(out-of-sequence thrusting). Strains within thrust sheets
from the Kinlochewe region suggest 0%-20% layer parallel
shortening may develop in the footwall to an abandoned
thrust as a tip strain to a newly developing thrust.
Variations in strain may reflect variable propagation
rates; differential displacement has resulted in differential movement within thrust sheets.
Fault-bend folds (structurally necessary folds) have
developed following slip of thrust sheets across irregular
thrust surfaces and buckle folds have grown during shortening within the sheet. Extensional fault sheets (surge
zones) can be mapped out in the Briancon region which both
truncate and are flexured by thrust structures; important
extensional structures have developed during evolution of
the thrust belt
Tendzin, moine tibétain
No full textin Être moine. A. Herrou, D. Iogna-Prat et A. Poujeau (éds.), Hors-série n° 3, Histoire et religions, p. 64.International audienceno abstrac
Limiti e labirinti. Spazi e comunità allo specchio nell'"Ospedale Vecchio" di Parma tra basso Medioevo ed età moderna
No full textQuesto articolo cerca di affrontare la storia di un istituto ospedaliero dal punto di vista della relazione tra spazi e comunità residenti nel corso del tempo
Il sigillo di Ludovico II
No full textDescription of the lead seal attributed to Ludovic II, found during excavation at the abbey of San Silvestro di Nonantola. This is a particularly rare find and indicative of the importance of the Benedictine center during the early Middle Ages
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