scholarly journals ΤΗE PELAGONIAN NAPPE PILE IN NORTHERN GREECE AND FYROM. STRUCTURAL EVOLUTION DURING THE ALPINE OROGENY: A NEW APROACH

2017 ◽  
Vol 43 (1) ◽  
pp. 276 ◽  
Author(s):  
Ad. Kilias ◽  
W. Frisch ◽  
A. Avgerinas ◽  
I. Dunkl ◽  
G. Falalakis ◽  
...  
Keyword(s):  
Late Cretaceous ◽  
Late Jurassic ◽  
Structural Evolution ◽  
Shear Zones ◽  
Low Grade ◽  
Northern Greece ◽  
Alpine Orogeny ◽  
Clastic Sediments ◽  
History Of ◽  
Structural Levels

The geometry of kinematics and the deformation history of the Pelagonian nappe pile during the Alpine orogeny have been studied in Northern Greece and FYROM. Deformation was started in Middle-Late Jurassic time and was initially associated with ocean-floor subduction followed by ophiolites obduction, nappe stacking and duplication of the Pelagonian continent. The footwall Pelagonian segment from top to bottom was metamorphosed under greenschist to amphibolit facies conditions and a relative high pressure (T = 450o to 620o C and P = 12,5 to 8 kb). Blueschist facies metamorphic assemblages of Late Jurassic age are immediately developed between both hangingwall and footwall Pelagonian segments. Transgressive Late Jurassic-Early Cretaceous neritic limestones and clastic sediments on the top of the obducted ophiolites are maybe related to extension and basins formation simultaneously with the nappe stacking and metamorphism at the lower structural levels of the Pelagonian nappes. Contractional tectonics and nappe stacking continued during the Albian-Aptian time. Simultaneously retrogression and pressure decreasing taken place at the tectonic lower Pelagonian footwall segment. Low grade mylonitic shear zones, possible related to extension, are developed during Late Cretaceous time simultaneously with basins formation and sedimentation of neritic Late Cretaceous to Paleocene limestones and flysch. Intense shortening and imbrication under semi-ductile to brittle conditions occurred during Paleocene to Eocene time resulting the onset of the dome like formation of the footwall Pelagonian segment. The next stages of deformation from Oligocene to Quaternary are related to brittle extension and the final uplift and configuration of the Pelagonian nappe pile.

scholarly journals A step towards unraveling the paleogeographic attribution of pre-Mesozoic basement complexes in the Western Alps based on U–Pb geochronology of Permian magmatism

2020 ◽  
Vol 113 (1) ◽  
Author(s):  
Michel Ballèvre ◽  
Audrey Camonin ◽  
Paola Manzotti ◽  
Marc Poujol
Keyword(s):  
Early Stage ◽  
Western Alps ◽  
Geochemical Data ◽  
Alkaline Magmatism ◽  
Low Grade ◽  
Calc Alkaline ◽  
Alpine Orogeny ◽  
History Of ◽  
External Part ◽  
The One

Abstract The Briançonnais Domain (Western Alps) represented the thinned continental margin facing the Piemonte-Liguria Ocean, later shortened during the Alpine orogeny. In the external part of the External Briançonnais Domain (Zone Houillère), the Palaeozoic basement displays microdioritic intrusions into Carboniferous sediments and andesitic volcanics resting on top of the Carboniferous sediments. These magmatic rocks are analysed at two well-known localities (Guil volcanics and Combarine sill). Geochemical data show that the two occurrences belong to the same calc-alkaline association. LA-ICP-MS U–Pb ages have been obtained for the Guil volcanics (zircon: 291.3 ± 2.0 Ma and apatite: 287.5 ± 2.6 Ma), and the Combarine sill (zircon: 295.9 ± 2.6 Ma and apatite: 288.0 ± 4.5 Ma). These ages show that the calc-alkaline magmatism is of Early Permian age. During Alpine orogeny, a low-grade metamorphism, best recorded by lawsonite-bearing veins in the Guil andesites, took place at about 0.4 GPa, 350 °C in the External Briançonnais and Alpine metamorphism was not able to reset the U–Pb system in apatite. The Late Palaeozoic history of the Zone Houillère is identical to the one recorded in the Pinerolo Unit, located further East in the Dora-Maira Massif, and having experienced a garnet-blueschist metamorphism during the Alpine orogeny. The comparison of these two units allows for a better understanding of the link between the Palaeozoic basements, mostly subducted during the Alpine convergence, and their Mesozoic covers, generally detached at an early stage of the convergence history.

scholarly journals The Kilen Expedition 1985

1993 ◽  
Vol 40 ◽  
pp. 9-32
Author(s):  
E. Håkansson ◽  
C. Heinberg ◽  
C. Hjort ◽  
P. Mølgaard ◽  
S. A. S. Pedersen
Keyword(s):  
Late Cretaceous ◽  
Late Jurassic ◽  
Higher Plants ◽  
Mobile Belt ◽  
Pull Apart Basin ◽  
Late Cretaceous Period ◽  
History Of ◽  
Entire Sequence ◽  
Cretaceous Period ◽  
Inland Ice

The 1985 expedition constitutes the first comprehensive investigation of the isolated, hyperarctic semi­nunatak Kilen in eastern North Greenland. Well over 3 km of generally marine, elastic sediments are preserved from the Late Jurassic to Late Cretaceous period. While half this amount accumulated in ·a comparatively stable tectonic regime prevailing during Late Jurassic and Early Cretaceous time, the Late Cretaceous (Turonian-Coniacian) sediments are characterized by their deposition in a local pull-apart basin developed in the regional Wandel Hav Strike-Slip Mobile Belt. Subsequent, localized compression along this belt has deformed the entire sequence rather severely in a complex series of en echelon domal folding and thrusting, most likely during the later part of the Cretaceous. Quaternary marine sediments of probable interglacial origin (> 100.000 years old) have been found to contain a mollusc fauna requiring temperatures above the present level. Flade lsblink, the largest local icecap in Greenland, is composed of several semi-independant ice domes, and there is evidence that the history of this icecap deviates significantly from that of the Inland Ice. A total of 34 species of higher plants, 29 species of birds, and 11 species of mammals have been recorded from Kilen; vegetation studies indicate a July mean temperature of around 2.5°C.

The skeletal morphology of the solemydid turtleNaomichelys speciosafrom the Early Cretaceous of Texas

2014 ◽  
Vol 88 (6) ◽  
pp. 1257-1287 ◽  
Author(s):  
Walter G. Joyce ◽  
Juliana Sterli ◽  
Sandra D. Chapman
Keyword(s):  
North America ◽  
Late Cretaceous ◽  
Lower Cretaceous ◽  
Fossil Record ◽  
Posterior Margin ◽  
Late Jurassic ◽  
Evolutionary History ◽  
Ventral View ◽  
Skeletal Morphology ◽  
History Of

The fossil record of solemydid turtles is primarily based on isolated fragments collected from Late Jurassic to Late Cretaceous sediments throughout North America and Europe and little is therefore known about the morphology and evolutionary history of the group. We here provide a detailed description of the only known near-complete solemydid skeleton, which was collected from the Lower Cretaceous (Aptian–Albian) Antlers Formation of Texas during the mid-twentieth century, but essentially remains undescribed to date. Though comparison is limited, the skeleton is referred toNaomichelys speciosa, which is based on an isolated entoplastron from the Lower Cretaceous (Aptian–Albian) Kootenai (Cloverly) Formation of Montana. The absence of temporal emarginations, contribution of the jugals to the orbits, and a clear subdivision of the middle and inner cavities, and the presence of elongate postorbitals, posteriorly expanded squamosals, a triangular fossa at the posterior margin of the squamosals, an additional pair of tubercula basioccipitale that is formed by the pterygoids, foramina pro ramo nervi vidiani (VII) that are visible in ventral view, shell sculpturing consisting of high tubercles, a large entoplastron with entoplastral scute, V-shaped anterior peripherals, and limb osteoderms with tubercular sculpture diagnoseNaomichelys speciosaas a representative of Solemydidae. The full visibility of the parabasisphenoid complex in ventral view, the presence of an expanded symphyseal shelf, and the unusual ventromedial folding of the coronoid process are the primary characteristics that distinguishNaomichelys speciosafrom the near-coeval European taxonHelochelydra nopcsai.

The geology and structure of the mid-crustal Wawa gneiss domain: a key to understanding tectonic variation with depth and time in the late Archean Abitibi–Wawa orogen

1994 ◽  
Vol 31 (7) ◽  
pp. 1064-1080 ◽  
Author(s):  
D. E. Moser
Keyword(s):  
Structural Evolution ◽  
Shear Zones ◽  
Fault Reactivation ◽  
Upper Crust ◽  
Middle Crust ◽  
Tectonic Events ◽  
Granulite Metamorphism ◽  
Stage 1 ◽  
Structural Levels ◽  
East West

The amphibolite-facies central Wawa gneiss domain (CWGD) preserves structures that developed at the mid-crustal level of the ca. 2.7 Ga Abitibi–Wawa orogen in the southern Superior Province. The relative ages of these domainal structures are documented and brackets on their absolute ages established using existing U–Pb age data. Correlation of tectonic events within the CWGD, and comparison of these events with the evolution of other structural levels of the orogen, has led to subdivision of orogenesis into five stages. During stage 1 (2700–2680 Ma), 2.9 and 2.7 Ga rocks were tightly folded and (or) thrusted at all crustal levels in at least one thick-skinned compression event. During stage 2 (2680–2670 Ma), folding and thrusting of Timiskaming-age sediments at high levels of the orogen was thin-skinned and had no effect on CWGD gneisses. During stage 3 (2670–2660 Ma), while the upper crust was relatively stable, a 1 km thick package of volcanics and sediments, the Borden Lake belt, was underthrust northwards to depths of 30 km and in-folded with orthogneiss of the CWGD. During stage 4 (2660–2637 Ma), coeval east–west extension and granulite metamorphism of the middle crust produced gently dipping shear zones that overprinted earlier fold structures in the CWGD and lower structural levels of the orogen. This took place with minimal effect on the upper crust. Stage 5 (2630–2580 Ma) marks a period of east–west shortening and (or) fault reactivation in the Kapuskasing uplift and upper-crustal greenstone belts that allowed penetration of deep-crustal metamorphic fluids into the latter. In general, analysis of the structural evolution of the CWGD indicates that deformation and metamorphism in the middle crust of the Abitibi–Wawa orogen outlasted that at upper-crustal levels, resulting in the generally shallower dips of planar fabrics in the deeper structural levels of the Kapuskasing uplift crustal cross section.

scholarly journals Stratigraphic and Structural Setting

1985 ◽  
Vol 4 (1) ◽  
pp. 1-10 ◽  
Author(s):  
A. El-Arnauti ◽  
M. Shelmani
Keyword(s):  
Marine Sediments ◽  
Early Cretaceous ◽  
Late Cretaceous ◽  
Late Jurassic ◽  
The West ◽  
Southeastern Part ◽  
Younger Age ◽  
History Of ◽  
Sirte Basin ◽  
Cretaceous Deposits

Abstract. INTRODUCTIONThe material which forms the basis of this project was obtained from a number of wells in the study area in Cyrenaica, the northeastern part of Libya. The study area, which is located between latitudes 25° and 33°N and between longitudes 20° and 25° E, covers some 365,750 square kilometres (see Fig. 1). The area extends from the Egyptian border in the east to the eastern flank of the Sirte Basin in the west and is part of the stable Saharan Shield.Since Precambrian time several phases of epeirogenic movements have produced troughs, horst blocks or platforms which have in turn influenced the subsequent sedimentological history of the area. In the southern and southeastern part of the study area, the basement is unconformably overlain by a thick, partially marine Palaeozoic sequence which is in turn unconformably overlain by sediments of Jurassic or younger age. The basement in the central and southwestern parts of the area is unconformably overlain by non-marine clastics of Late Jurassic and Early Cretaceous age or by marine sediments of Late Cretaceous and Tertiary age. In the eastern and northeastern section the basement is overlain by a wedge of eastward thickening marine Palaeozoic rocks which are in turn unconformably overlain by marine sediments of Late Cretaceous and Tertiary age. In the most northerly part of the northeastern region of the study area, a thick paralic sequence of Triassic, Jurassic and Early Cretaceous deposits is unconformably overlain by Late Cretaceous and Tertiary sediments.PALAEOZOICRocks of Cambro-Ordovician . . .

scholarly journals Deconstructing the Infrastructure: A Complex History of Diachronous Metamorphism and Progressive Deformation during the Late Cretaceous to Eocene in the Thor-Odin–Pinnacles Area of Southeastern British Columbia

2016 ◽  
Vol 43 (2) ◽  
pp. 103 ◽  
Author(s):  
Deanne Van Rooyen ◽  
Sharon D. Carr
Keyword(s):  
British Columbia ◽  
Late Cretaceous ◽  
Normal Fault ◽  
Columbia River ◽  
Metamorphic Rocks ◽  
High Grade ◽  
Basement Rocks ◽  
History Of ◽  
Complex Structural ◽  
Structural Levels

The Thor-Odin dome is a basement-cored tectonothermal culmination in southern British Columbia containing high-grade metamorphic rocks that were polydeformed in the Late Cretaceous to Eocene. The rocks south of the Thor-Odin dome that extend ca. 20 km to the Pinnacles culmination and Whatshan batholith comprise a heterogeneous tract of polydeformed medium- to high-grade metamorphic rocks and host the South Fosthall pluton near the base of the structural section. They lie in the footwall of the Columbia River fault (CRF) zone, a moderately east-dipping, ductile-brittle, normal fault that was active after ca. 55 Ma and reactivated periodically up to 30 Ma. This tract of rocks has been interpreted as a mid-crustal zone that was exhumed and cooled during Eocene extension or, alternatively, a mid-crustal channel that was bounded at the top by the CRF and was active during the Late Cretaceous to Eocene. However, the timing of metamorphism, deformation, anatexis in basement rocks, and intrusion of leucogranite plutons reveals that there are four tectonothermal domains within the tract that each experienced metamorphism, deformation and cooling at different times. These rocks record Cretaceous metamorphism and cooling in the upper structural levels and three stages of progressive metamorphism and penetrative deformation that migrated into deeper crustal levels in the Paleocene and Eocene producing a complex structural section that was exhumed in part due to motion on the Columbia River fault zone, and in part due to NE-directed transport over a basement ramp.RÉSUMÉLe dôme de Thor-Odin correspond à une culmination tectonothermique d’un noyau de socle dans le sud de la Colombie-Britannique renfermant des roches métamorphiques de haute intensité polydéformées entre le Crétacé supérieur et l’Éocène. Les roches au sud du dôme de Thor-Odin qui s’étendent sur environ 20 km jusqu’à la culmination des Pinnacles et du batholite de Whatshan sont constituées d’une bande hétérogène de roches polydéformées à faciès métamorphique d’intensité moyenne à élevée qui constitue l’encaissant du pluton de South Fosthall près de la base de la colonne structurale. Elles se trouvent dans l'éponte inférieure de la zone de faille de la rivière Columbia (CRF), une faille normale à pendage modéré vers l’est, ductile-fragile, qui a été active après 55 Ma environ et a été réactivée périodiquement jusqu'à 30 Ma. Cette bande de roches a été interprétée comme une zone de mi-croûte qui a été exhumée et a refroidi durant l’extension éocène ou alors comme un canal mi-crustal qui a été limité au sommet par la CRF, et qui a été actif de la fin du Crétacé jusqu’à l’Éocène. Toutefois, la chronologie du métamorphisme, de la déformation, de l’anatexie dans les roches du socle, et de l'intrusion de plutons de leucogranite, montre qu'il existe quatre domaines tectonothermiques pour chaque bande qui ont subit du métamorphisme, de la déformation et du refroidissement à différents moments. Ces roches exhibent un métamorphisme et un refroidissement crétacé dans les niveaux structuraux supérieurs et trois stades de métamorphisme progressif et de déformation pénétrative qui ont migré dans les niveaux crustaux profonds au Paléocène et à l’Eocène constituant ainsi une colonne structurale complexe qui a été exhumée en partie en raison du mouvement de la zone de faille de Columbia River, et en partie en raison du transport vers le N.-E. sur une rampe de socle.

scholarly journals Rhabdophane Th-Pb ages indicate reactivation of Mesoarchean structures in west Pilbara Craton during breakup of Greater India and Australia-Antarctica

Geology ◽  
2021 ◽  
Author(s):  
Birger Rasmussen ◽  
Jian-Wei Zi ◽  
Janet R. Muhling
Keyword(s):  
Fluid Flow ◽  
Shear Zones ◽  
Drill Hole ◽  
Carbonaceous Shale ◽  
Low Grade ◽  
Early Environment ◽  
Metasedimentary Rocks ◽  
Rift Propagation ◽  
History Of ◽  
Pilbara Craton

Uranium-Th-Pb dating of phosphate minerals in very low-grade metasedimentary rocks from the Archean Pilbara Craton, Western Australia, has revealed a long history of deformation and fluid flow during the Paleoproterozoic. However, this technique has not detected evidence for fluid flow along craton margins during Phanerozoic rifting and breakup. We report the use of in situ Th-Pb geochronology of rhabdophane, a hydrous light rare earth element phosphate, to date fluid flow in shale from the 2.76 Ga Mount Roe Basalt from drill hole number 6 of the Archean Biosphere Drilling Program (ABDP6), northwestern Pilbara Craton. Thorium-Pb dating of rhabdophane in carbonaceous shale yields three main populations with weighted mean 208Pb/232Th ages of 152 ± 6 Ma, 132 ± 4 Ma, and 119 ± 4 Ma, which indicates phosphate growth up to 2.64 b.y. after deposition. The rhabdophane ages are coeval with three major breakup events in eastern Gondwana: separation of Southwest Borneo and Argoland from Australia (ca. 156–152 Ma), breakup of Greater India from Australia (ca. 140–135 Ma), and separation of Greater India/India from Antarctica (ca. 123 Ma). The proximity of drill hole ABDP6 to major Mesoarchean faults and shear zones on the craton margin, which are parallel to rift propagation and basin development, points to episodic reactivation of ancient crustal structures >2.8 b.y. after their formation. Our results also highlight the potential of rhabdophane as a U-Th-Pb geochronometer for dating low-temperature (<200 °C) fluid flow and hydrous alteration. The migration of Mesozoic fluids through Archean shales adds weight to questions about the origin of geochemical signals in ancient altered rocks and how to extract information about the early environment and biosphere.

scholarly journals Origin of sediments during Cretaceous continent—continent collision in the Romanian Southern Carpathians: preliminary constraints from 40Ar/39Ar single-grain dating of detrital white mica

2013 ◽  
Vol 64 (5) ◽  
pp. 375-382 ◽  
Author(s):  
Franz Neubauer ◽  
Ana-Voica Bojar
Keyword(s):  
Late Jurassic ◽  
Upper Cretaceous ◽  
Shear Zones ◽  
White Mica ◽  
Low Grade ◽  
Late Permian ◽  
Ductile Shear Zones ◽  
Single Grain ◽  
Ductile Shear ◽  
Southern Carpathians

Abstract Single grains of detrital white mica from the lowermost Upper Cretaceous Sinaia Flysch have been dated using the 40Ar/39Ar technique. The Sinaia Flysch was deposited in a trench between the Danubian and Getic microcontinental pieces after the closure of the Severin oceanic tract. The Danubian basement is largely composed of a Panafrican/Cadomian basement in contrast to the Getic/Supragetic units with a Variscan-aged basement, allowing the distinction between these two blocks. Dating of detrital mica from the Sinaia Flysch resulted in predominantly Variscan ages (329 ± 3 and 288 ± 4 Ma), which prove the Getic/Supragetic source of the infill of the Sinaia Trench. Subordinate Late Permian (263 ± 8 and 255 ±10 Ma), Early Jurassic (185 ± 4 and 183 ± 3 Ma) and Late Jurassic/Early Cretaceous (149 ± 3 and 140 ± 3 Ma) ages as well as a single Cretaceous age (98 ± 4 Ma) are interpreted as representing the exposure of likely retrogressive low-grade metamorphic ductile shear zones of various ages. Ductile shear zones with similar 40Ar/39Ar white mica ages are known in the Getic/Supragetic units. The Cretaceous ages also show that Cretaceous metamorphic units were already subject to erosion during the deposition of the Sinaia Flysch.

STRUCTURAL FRAMEWORK AND BASIN EVOLUTION OF AUSTRALIA’S SOUTHERN MARGIN

2003 ◽  
Vol 43 (1) ◽  
pp. 13 ◽  
Author(s):  
J.P. Teasdale ◽  
L.L. Pryer ◽  
P.G. Stuart-Smith ◽  
K.K. Romine ◽  
M.A. Etheridge ◽  
...  
Keyword(s):  
Late Cretaceous ◽  
Structural Control ◽  
Structural Evolution ◽  
Shear Zones ◽  
Basin Evolution ◽  
Primary Control ◽  
Fold Belt ◽  
Southern Margin ◽  
Lachlan Fold Belt ◽  
Basement Structures

The structural evolution of all of the Southern Margin Basins can be explained by episodic reactivation of basement structures in respect to a specific sequence of tectonic events. Three geological provinces dominate the basement geology of the Southern Margin basins. The Eyre, Ceduna, Duntroon and Polda Basins overlie basement of the Archean to Proterozoic Gawler-Antarctic Craton. The Otway and Sorell Basins overlie basement of the Neoproterozoic-early Palaeozoic Adelaide- Kanmantoo Fold Belt. The Bass and Gippsland Basins overlie basement of the Palaeozoic Lachlan Fold Belt. The contrasting basement terranes within the three basement provinces and the structures within and between them significantly influenced the evolution and architecture of the Southern Margin basins.The present-day geometry was established during three Mesozoic extensional basin phases:Late Jurassic–Early Cretaceous NW–SE transtension forming deep rift basins to the west and linked pullapart basins and oblique graben east of the Southwest Ceduna Accommodation Zone; Early–Mid Cretaceous NE–SW extension; and Late Cretaceous NNE–SSW extension leading to continental breakup. At least three, potentially trap forming, inversion events have variably influenced the Southern Margin basins; Mid Cretaceous, Eocene, and Miocene-Recent. Volcanism occurred along the margin during the Late Cretaceous and sporadically through the Tertiary.First-order structural control on Mesozoic rifting and breakup were east–west trending basement structures of the southern Australian fracture zone. Second-order controls include:Proterozoic basement shear zones and/or terrane boundaries in the western Gawler Craton, which controlled basin evolution in the Eyre and Ceduna Subbasins; Neoproterozoic structures, which significantly influenced basin evolution in the Ceduna sub-basin; Cambro-Ordovician basement shear zones and/or terrane boundaries, which were a primary control on basin evolution in the Otway and Sorell Basins; and Palaeozoic structures in the Lachlan Fold Belt, which controlled basin evolution in the Bass and Gippsland Basins.A SEEBASE™ (Structurally Enhanced view of Economic Basement) model for the Southern Margin basins has been constructed to show basement topography. When used in combination with a rigorous interpretation of the structural evolution of the margin, it provides a foundation for basin phase and source rock distribution, hydrocarbon fluid focal points and trap type/distribution.

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