| 1. |
- Ahlberg, Anders, et al.
(författare)
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Onshore climate change during the late triassic marine inundation of the Central European Basin
- 2002
-
Ingår i: Terra Nova: the European journal of geosciences. - : Wiley. - 0954-4879. ; 14:4, s. 241-248
-
Tidskriftsartikel (refereegranskat)abstract
- Sedimentological, pedological and palynological evidence reveal radically increasing onshore humidity during the Rhaetian marine invasion of central Europe along the north-eastern margin of the Central European Basin (southern Sweden). Pre-Rhaetian aridity favoured the formation of Carnian redbeds with calcrete, which were succeeded by Norian hematite-cemented conglomerates, arkoses, arkosic wackestones, and smectititic mudstones deposited on braidplains and in lakes. Superimposed autochthonous coals and gleysols indicate the Rhaetian onset of year-round humidity. Chemically mature sandstones, kaolinitic mudstones and luvisols also formed at this time, influenced by a permanent vegetation cover which lowered soil pH and strongly intensified chemical weathering. The Rhaetian deposits accumulated in floodplain lakes repeatedly subjected to sediment infill, plant colonization and palaeosol development. The humidity shift resembles that contemporaneously recorded in the North Sea region.
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| 2. |
- Andréasson, Per-Gunnar, et al.
(författare)
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Subduction-flip during Iapetus Ocean closure and Baltica-Laurentia collision, Scandinavian Caledonides
- 2003
-
Ingår i: Terra Nova: the European journal of geosciences. - : Wiley. - 0954-4879. ; 15:6, s. 362-369
-
Tidskriftsartikel (refereegranskat)abstract
- Evidence is presented here from the northern Scandinavian Caledonides for development of an extensional basin of Ashgill to Mid Llandovery age along the Baltoscandian margin immediately prior to Baltica-Laurentia collision. U/Pb multigrain and ion microprobe zircon dating of plagiogranites in the Halti Igneous Complex complement previous baddeleyite and zircon dating of a dolerite dyke, and zircon dating of anatectic granite; they demonstrate that this dunite, troctolite, gabbro, sheeted-dyke complex ranges in age from c. 445 to 435 Ma. The dolerite dykes intruded and melted arkoses of inferred Neoproterozoic age. This evidence, taken together with previous documentation of ophiolites (Solund-Stavfjord), ophiolite-like associations (Sulitjelma Igneous Complex) and several other mafic suites (e.g. Rana, Artfjallet) of Ashgill to Llandovery age further south in the northern Scandinavian Caledonides, implies that Scandian collisional orogeny along this nearly 2000-km-long mountain belt was immediately preceeded by development of short-lived marginal basins. The latter developed during the final closure of the Iapetus Ocean and are inferred to be of back-arc origin, some (perhaps all) related to E-dipping subduction. Collision of the continents at c. 435 Ma is inferred to have induced a flip in subduction polarity, leading to underthrusting of Laurentia by Baltica.
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| 3. |
- Wastegard, S, et al.
(författare)
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A tephra-based correlation between the Faroe Islands and the Norwegian Sea raises questions about chronological relationships during the last interglacial
- 2005
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Ingår i: Terra Nova: the European journal of geosciences. - : Wiley. - 0954-4879. ; 17:1, s. 7-12
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Tidskriftsartikel (refereegranskat)abstract
- Marine ash zones from the last interglacial period have been described from cores from the North Atlantic and an ash zone from the middle part of the interglacial has been observed in connection with a major cooling event. Here we present evidence for a coeval ash zone in a terrestrial site on the Faroe Islands. The investigated sediments are correlated with the upper part of oxygen isotope stage 5e and the beginning of stage 5d. The Eemian climatic optimum is represented in the lower part of the sequence close to the first occurrence of the ash zone. A tephra-based correlation suggests that the climatic optimum was synchronous with the marine record from the Norwegian Sea, but several thousand years later than in Eemian sections of west central Europe. However, many questions on the chronological relationship between the Eemian and oxygen isotope stage 5e still remain to be answered.
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| 4. |
- Ask, Maria, et al.
(författare)
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In-situ stress determination from breakouts in the Tornquist Fan, Denmark
- 1996
-
Ingår i: Terra Nova. - : Wiley. - 0954-4879 .- 1365-3121. ; 8:6, s. 575-584
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Tidskriftsartikel (refereegranskat)abstract
- The Tornquist Fan, a fan-shaped region in Denmark and Western Baltic, is situated in the transition zone between the Western and Northern European Stress Provinces. Breakout data from 20 wells (0.3-3.6 km) were analysed. The fan can be divided into three stress provinces: (i) The area south of the Romo Fracture Zone is part of the Western European Stress Province and has NNW-SSE orientation of the maximum horizontal stress, (ii) The sediment cover in the Norwegian-Danish Basin is dominated by ENE-WSW orientated maximum horizontal stress, (iii) The maximum horizontal stress is sub-parallel to the strike of the Sorgenfrei-Tornquist Zone. Deviations from the regional stress field were observed in wells close to faults and salt diapirs. In wells south of the Sorgenfrei-Tornquist Zone, breakout occurrence decreases with increasing age of the stratigraphic units. The downhole breakout distribution seems to correlate with lithology and thickness of the sediment layer.
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| 5. |
- Friberg, M, et al.
(författare)
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Europrobe seismic reflection profiling across the eastern Middle Urals and West Siberian Basin
- 2001
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Ingår i: Terra Nova. - : Blackwell Publishing. - 0954-4879 .- 1365-3121. ; 12:6, s. 252-257
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Tidskriftsartikel (refereegranskat)abstract
- New deep seismic reflection data provide images of the crust and uppermost mantle underlying the eastern Middle Urals and adjacent West Siberian Basin. Distinct truncations of reflections delineate the late-orogenic strike-slip Sisert Fault extending vertically to ∼28 km depth, and two gently E-dipping reflection zones, traceable to 15–18 km depth, probably represent normal faults associated with the opening of the West Siberian Basin. A possible remnant Palaeozoic subduction zone in the lower crust under the West Siberian Basin is visible as a gently SW-dipping zone of pronounced reflectivity truncated by the Moho. Continuity of shallow to intermediate-depth reflections suggest that Palaeozoic accreted island-arc terranes and overlying molasse sequences exposed in the hinterland of the Urals form the basement for Triassic and younger deposits in the West Siberian Basin. A highly reflective lower crust overlies a transparent mantle at about 43 km depth along the entire 100 km long seismic reflection section, suggesting that the lower crust and Moho below the eastern Middle Urals and West Siberian Basin have the same origin.
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| 6. |
- Juhlin, Christopher, et al.
(författare)
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Moho imbrication in the Middle Urals
- 2007
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Ingår i: Terra Nova. - : Wiley. - 0954-4879 .- 1365-3121. ; 19:3, s. 189-194
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Tidskriftsartikel (refereegranskat)abstract
- New processing of part of the Europrobe's Seismic Reflection Profiling in the Urals (ESRU) reflection seismic data in the Middle Urals shows a southwest-dipping Moho imbrication and crustal underthrusting that was not previously imaged. The area of thickening associated with it roughly coincides with a deepening of the Moho imaged by the GRANIT refraction data. This feature does not fit with the currently known Palaeozoic crustal architecture of the Uralides or with its geodynamic history. Geological data suggest that it is not related to a relict southwest-dipping subduction zone. Based on its lower crustal and Moho reflection seismic character it is presently interpreted to be a post-Uralide feature, possibly related to Mesozoic intraplate shortening in the area. Its coincidence with a locus of mild earthquake activity further suggests that it might be active today.
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| 7. |
- Lindroos, Alf, et al.
(författare)
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Late-orogenic Svecofennian deformation in SW Finland constrained by pegmatite emplacement ages
- 1996
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Ingår i: Terra Nova. - : Wiley. - 0954-4879 .- 1365-3121. ; 8:6, s. 567-574
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Tidskriftsartikel (refereegranskat)abstract
- Late stages of the Svecofennian orogeny in SW Finland were related to a tranpressional stress field and dextral movements along crustal scale shear zones under decreasing temperature and pressure conditions. In the Kemiö area, a minimum estimate for the time span of movements along one of these shear zones is obtained from the ages of 1840 to 1830 Myr-old microcline granite sheets, related to early ductile deformation, and by dating structurally late rare-mineral granite pegmatites, related to brittle deformation. One pegmatite was emplaced when the rheological conditions in the gabbro changed from ductile to semi-ductile and brittle. It has U-Pb ferrotapiolite ages ranging between 1807.0 ± 2.9 Myr (2 ) and 1803.1 + 2.9/ -2.0 Myr (2 ). Another pegmatite emplaced under brittle conditions has an U-Pb ferrotapiolite age of 1802.9 ± 1.3 Myr (2 ). These pegmatites were emplaced preferentially in gabbroic rocks, that showed brittle to semi-ductile deformation at a time when their more felsic host-rocks still showed ductile deformation. The age range bracketed by the microcline granite sheets and the structurally late pegmatites indicates that ductile deformation related to the transpressional Late Svecofennian tectonic regime in southwestern Finland, persisted for at least 30-40 Myr
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| 8. |
- Romer, Rolf
(författare)
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Contiguous Laurentia and Baltica before the Grenvillian-Sveconorwegian orogeny?
- 1996
-
Ingår i: Terra Nova. - : Wiley. - 0954-4879 .- 1365-3121. ; 8:2, s. 173-181
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Tidskriftsartikel (refereegranskat)abstract
- Close geochronological correspondence of Mesoproterozoic extension-related magmatism and comparable tectonic and geochronological evolution of the Grenville and Svecononvegian orogens suggests that the Laurentian and Baltic Shields could have been joined during the Mesoproterozoic and did not separate until after the Grenvillian-Sveconorwegian orogeny. The combined Grenville-Svecononvegian orogen is here interpreted to have formed during the collision of coherent Laurentia-Baltica with an unknown craton, which is in contrast to earlier explanations that favour a late-Mesoproterozoic rotation between Laurentia and Baltica followed by collision of these two cratons with each other
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| 9. |
- Shumlyanskyy, Leonid, et al.
(författare)
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U-Pb age and Hf isotope compositions of zircons from the north-western region of the Ukrainian shield : mantle melting in response to post-collision extension
- 2012
-
Ingår i: Terra Nova. - : Wiley. - 0954-4879 .- 1365-3121. ; 24:5, s. 373-379
-
Tidskriftsartikel (refereegranskat)abstract
- The North-Western region of the Ukrainian shield represents Palaeoproterozoic continental crust formed essentially during two orogenic events at ca. 2.1–2.05 and 2.0–1.95 Ga. At 1.8–1.74 this area was intruded by huge Korosten anorthosite–mangerite–charnockite granite complex. At least three generations of mafic dykes can be distinguished in the region. We report new U-Pb data obtained for a suite of Ni-enriched dolerite dykes and layered gabbroic intrusions. Our results indicate that the Tomashgorod dyke was formed at 1787.4 ± 6.4 Ma, the Prutivka intrusion at 1777.0 ± 4.7 Ma and the Kamenka massif at ca. 1.79 Ga. This time coincides with the collision of the Fennoscandian and Sarmatian segments of the East European craton and it is contemporaneous with the initial stages of evolution of the Korosten complex. Hf isotopic compositions of zircons indicate that these rocks originated due to melting of moderately depleted mantle material.
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| 10. |
- Wikström, A., et al.
(författare)
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The Bälinge conglomerate in northern Sweden reinterpreted as a magmatic, hydraulic breccia
- 1996
-
Ingår i: Terra Nova. - : Wiley. - 0954-4879 .- 1365-3121. ; 8:2, s. 166-172
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Tidskriftsartikel (refereegranskat)abstract
- The Bälinge conglomerate has played a key role in the lithostratigraphy of northern Sweden. The conglomerate, with pebbles dominated by granodiorites and tonalites in a generally biotite-rich matrix, borders volcanic rocks with unclear relative age relationships. In nearby areas these volcanites have been intruded by plutonic rocks (c. 1.9 Ga) which are similar to the pebble material. On these grounds, the conglomerate has been regarded as younger than the volcanic rocks and an important marker in the geological evolution of the region. In this preliminary study, it is suggested that the features displayed by the Balinge conglomerate are not compatible with an epiclastic origin. On the contrary, they indicate that this rock represents a hydraulic breccia where the roundness of the granitoid 'pebbles' has resulted from erosion in a fluidised, heterogeneous and magmatic environment. In the actual area the 'conglomerate' must thus be dismissed as a stratigraphic marker horizon. It belongs to the early Svecofennian evolution.
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| 11. |
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| 12. |
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| 13. |
- Bazarnik, Jakub, et al.
(författare)
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U-Pb zircon dating of metaigneous rocks from the Nordbreen Nappe of Svalbard's Ny-Friesland suggests their affinity to Northeast Greenland
- 2019
-
Ingår i: Terra Nova. - : WILEY. - 0954-4879 .- 1365-3121. ; 31:6, s. 518-526
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Tidskriftsartikel (refereegranskat)abstract
- SIMS U-Pb zircon dating of metaigneous rocks of the Nordbreen Nappe from the West Ny-Friesland terrane (Eastern Basement Province of Svalbard) yields crystallization ages of 1,761 +/- 4 Ma for a felsic metatuff and 1,373 +/- 4 Ma for a metagabbro dyke. The Palaeoproterozoic age of the metatuff is similar to previously obtained ages for various felsic rocks from the study area, whereas the Mesoproterozoic age of the metagabbro has not been thus far documented on Svalbard. However, a similar age pattern has been reported from Northeast Greenland. Therefore, we conclude that the West Ny-Friesland terrane can be correlated with age equivalent units of Northeast Greenland. We also explore similarities and dissimilarities between the study area and other terranes of Svalbard and speculate on regional-scale correlations. Together, the presented new ages provide critical piercing points in palaeogeographic reconstructions of the relatively poorly understood circum-Arctic region.
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| 14. |
- Brengman, L., et al.
(författare)
-
Micro-scale silicon isotope heterogeneity observed in hydrothermal quartz precipitates from the >3.7 Ga Isua Greenstone Belt, SW Greenland.
- 2016
-
Ingår i: Terra Nova. - : Wiley. - 0954-4879 .- 1365-3121. ; 28, s. 70-75
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Tidskriftsartikel (refereegranskat)abstract
- Pillow basalt and chert form integral lithologies comprising many Archean greenstone belt packages. To investigate details of these lithologies in the >3.7 Ga Isua Greenstone Belt, SW Greenland, we measured silicon isotope compositions of quartz crystals, by secondary ion mass spectrometry, from a quartz-cemented, quartz-amygdaloidal basaltic pillow breccia, recrystallized chert and chert clasts thought to represent silica precipitation under hydrothermal conditions. The recrystallized chert, chert clasts and quartz cement have overlapping δ30Si values, while the δ30Si values of the quartz amygdules span nearly the entire range of previously published values for quartz precipitates of any age, despite amphibolite facies metamorphism. We suggest that the heterogeneity is derived from kinetic isotope fractionation during quartz precipitation under disequilibrium conditions in a hydrothermal setting, consistent with the pillow breccia origin. On the basis of the present data, we conclude that the geological context of each sample must be carefully evaluated when interpreting δ30Si values of quartz.
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| 15. |
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| 16. |
- Faehnrich, Karol, et al.
(författare)
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Geochronological constraints on Caledonian strike-slip displacement in Svalbard, with implications for the evolution of the Arctic
- 2020
-
Ingår i: Terra Nova. - : Wiley. - 0954-4879 .- 1365-3121. ; 32:4, s. 290-299
-
Tidskriftsartikel (refereegranskat)abstract
- The timing of Svalbard's assembly in relation to the mid-Paleozoic Caledonian collision between Baltica and Laurentia remains contentious. The Svalbard archipelago consists of three basement provinces bounded by N-S-trending strike-slip faults whose displacement histories are poorly understood. Here, we report microstructural and mineral chemistry data integrated with Ar-40/Ar-39 muscovite geochronology from the sinistral Vimsodden-Kosibapasset Shear Zone (VKSZ, southwest Svalbard) and explore its relationship to adjacent structures and regional deformation within the circum-Arctic. Our results indicate that strike-slip displacement along the VKSZ occurred in late Silurian-Early Devonian and was contemporaneous with the beginning of the main phase of continental collision in Greenland and Scandinavia and the onset of syn-orogenic sedimentation in Silurian-Devonian fault-controlled basins in northern Svalbard. These new-age constraints highlight possible links between escape tectonics in the Caledonian orogen and mid-Paleozoic terrane transfer across the northern margin of Laurentia.
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| 17. |
- Frasca, Gianluca, et al.
(författare)
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A kinematic reconstruction of Iberia using intracontinental strike-slip corridors
- 2021
-
Ingår i: Terra Nova. - : John Wiley & Sons. - 0954-4879 .- 1365-3121. ; 33:6, s. 573-581
-
Tidskriftsartikel (refereegranskat)abstract
- Despite considerable progress in restoring rifted margins, none of the current kinematic models can restore the Mesozoic motion of the Iberian block in full agreement with the circum-Iberian geology. This conflict requires a revision of the kinematic description at the onset of divergence. The circum-Iberian region has a unique geological dataset that allows calibration and testing of kinematic reconstructions and therefore it is an ideal candidate for testing intracontinental restoration approaches. Here we define intracontinental deforming regions, referred to as strike-slip corridors, based on alignments of Mesozoic rift basins and/or transfer zones bordering rigid continental blocks. We use these strike-slip corridors and data from the southern N-Atlantic and Tethys to define the motion path of the Flemish Cap, Ebro and Iberia continental blocks. The resulting Mesozoic kinematic model for the Iberian block is compatible with recently published data and interpretations describing the Mesozoic circum-Iberian geology. Large-scale intracontinental strike-slip corridors may offer a valid boundary condition for reconstructing continental block motion at the onset of divergence in intracontinental settings.
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| 18. |
- Gernigon, Laurent, et al.
(författare)
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Understanding volcanic margin evolution through the lens of Norway's youngest granite
- 2024
-
Ingår i: Terra Nova. - : John Wiley & Sons. - 0954-4879 .- 1365-3121.
-
Tidskriftsartikel (refereegranskat)abstract
- Three boreholes drilled during the International Ocean Discovery Program (IODP) Expedition 396 have yielded unexpected findings of altered granitic rocks covered by basalt flows, interbedded sediments and glacial mud near the continent-ocean transition of the mid-Norwegian margin. U-Pb and K-Ar geochronological analyses were conducted on both protolithic and authigenically formed K-bearing minerals to determine the age of granite crystallisation and subsequent alteration episodes. The granite's crystallisation age based on 104 zircons is 56.3 ± 0.2 Ma, and subsequent exhumation along with alteration/weathering events took place between 54.7 ± 1 and 37.1 ± 1 Ma. This intrusion represents the youngest granite discovered in Norway and intruded at an extremely shallow crustal level before a rapid rift-to-drift transition. The shallow emplacement of granitic rock and its fast exhumation before and during the onset of volcanism holds significant implications for the syn- and post-breakup tectonic evolution of volcanic margins.
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| 19. |
- Goodfellow, Bradley W., et al.
(författare)
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Palaeocene faulting in SE Sweden from U-Pb dating of slickenfibre calcite
- 2017
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Ingår i: Terra Nova. - : Wiley. - 0954-4879 .- 1365-3121. ; 29:5, s. 321-328
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Tidskriftsartikel (refereegranskat)abstract
- Estimating the timing of faulting is crucial to modelling tectonics, palaeoseismicity, landscape evolution and fault mechanics. Four slickenfibre calcite samples from a conjugate strike-slip fault set in a platformal limestone, SE Sweden, were dated using U-Pb. Three of the samples yielded an average age of 64.8 +/- 6.5Ma, while the fourth yielded a marginally younger age of 54.7 +/- 5.5Ma. Precipitation of the fibres is interpreted as syn-deformational. Age uncertainty and dispersion reflect incorporation of common Pb and tiny host-rock components into the dated calcite and/or possible fault reactivation through ca. 55Ma. We infer from crystal characteristics, stable isotopes (O-18 and C-13) and rare-earth elements that fibres formed in an environment rich in deep-seated fluids, at temperatures of 40-200 degrees C, with shear stresses exceeding 10 MPa and at a maximum burial depth of c. 4km. This Palaeocene faulting may reflect far-field stresses from shortening in the Alps.
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| 20. |
- Kosminska, Karolina, et al.
(författare)
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Blueschist facies metamorphism in Nordenskiold Land of west-central Svalbard
- 2014
-
Ingår i: Terra Nova. - : Wiley. - 0954-4879 .- 1365-3121. ; 26:5, s. 377-386
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Tidskriftsartikel (refereegranskat)abstract
- Recent fieldwork in Nordenskiold Land, Svalbard's Southwestern Basement Province, has established the presence of high-pressure (HP) lithologies. They are strongly retrogressed blueschists consisting mainly of garnet and Ca-amphibole with remnants of ferroglaucophane and phengite. The pressure-temperature (P-T) conditions were estimated using phase equilibrium modelling in the NCKFMMnASHTO system. P-T estimates based on the garnet, phengite and ferroglaucophane compositional isopleths and modelled paragenetic assemblage indicate peak metamorphism at 470-490 degrees C and 14-18 kbar. These data fall close to the 7-8 C km(-1) geo-therm, which is similar to that from Motalafjella, the only previously known occurrence of blueschists in Svalbard's Caledonides. The newly discovered blueschists could have formed during the early stage of the Caledonian Orogeny and may represent a vestige of missing marginal basins of the western Iapetus developed at the onset of subduction. The likely counterpart to Svalbard's blueschists is the ophiolitic sequence in the Pearya Terrane of northern Ellesmere Island.
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| 21. |
- Lorenz, Henning, 1972-, et al.
(författare)
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Detrital zircon geochronology of Palaeozoic Novaya Zemlya – a key to understanding the basement of the Barents Shelf
- 2013
-
Ingår i: Terra Nova. - : Wiley. - 0954-4879 .- 1365-3121. ; 25:6, s. 496-503
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Tidskriftsartikel (refereegranskat)abstract
- The Novaya Zemlya fold-and-thrust-belt is the northern con- tinuation of the late Palaeozoic Uralide Orogen. Little is known about its deeper structure and the basement history of the adjacent Barents and Kara shelves. Based on geological evidence and detrital zircon analysis of 28 samples from the northeastern and stratigraphically deepest part of the archi- pelago, we demonstrate that Cambro-Ordovician turbidite- dominated deposition was almost exclusively sourced from rocks consolidated during the Timanian orogeny (Timanian basement). A profound change in provenance occurred near the end of the Ordovician. Over 90% of the zircons from Silu- rian and about 80% from Devonian strata have ages charac- teristic of the Sveconorwegian Orogen, implying uplift of these rocks in the vicinity of Novaya Zemlya. The presence of Sveconorwegian and Grenvillian rocks in the high Arctic sug- gests revision of recent reconstructions of the Rodinia super- continent, its break-up and subsequent Caledonian orogeny.
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| 22. |
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| 23. |
- Mazur, Stanislaw, et al.
(författare)
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Exhumation of the high-pressure Richarddalen Complex in NWSvalbard : Insights from Ar-40/(39)Argeochronology
- 2022
-
Ingår i: Terra Nova. - : John Wiley & Sons. - 0954-4879 .- 1365-3121. ; 34:4, s. 330-339
-
Tidskriftsartikel (refereegranskat)abstract
- Ar-40/Ar-39 dating of white mica from foliated metamorphic rocks of the Caledonian orogen of NW Svalbard was performed using the single-grain fusion technique. Two samples, an augen orthogneiss and a mica schist, were collected from the high-pressure Richarddalen Complex. Three additional mica schist samples were collected from the tectonically underlying Montblanc Unit. Ar-40/Ar-39 analysis of white mica separates yielded weighted average Ar-40/Ar-39 dates of 446.1 +/- 1.1, 438.4 +/- 1.1, 439.4 +/- 1.2, 439.8 +/- 1.5 and 439.3 +/- 1.0 Ma, with the oldest date provided by the Richarddalen mica schist. The single-grain fusion Ar-40/Ar-39 dating was accompanied by geochemical mapping of white mica using a microprobe. We interpret the oldest date as the age of cooling after a Late Ordovician high-pressure event and the four younger dates to represent the timing of subsequent deformation associated with assembly of a Caledonian nappe stack.
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| 24. |
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| 25. |
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| 26. |
- Rösel, D, et al.
(författare)
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Indo-Antarctic derived detritus on the northern margin of Gondwana: evidence for continental scale sediment transport
- 2014
-
Ingår i: Terra Nova. - : Wiley. - 0954-4879 .- 1365-3121. ; 26:1, s. 64-71
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Tidskriftsartikel (refereegranskat)abstract
- Provenance studies from Cambro-Ordovician sediments of the North Gondwana passive margin typically ascribe a North African source, a conclusion that cannot be reconciled with all observations. We present new U-Pb ages from detrital rutile and zircon from Late Ordovician sediments from Saxo-Thuringia, Germany. Detrital zircons yield age populations of 500–800 Ma, 900–1050 Ma and 1800–2600 Ma. The detrital rutile age spectra are unimodal with ages between 500 and 650 Ma and likely represent, together with the 500–800 Ma and 1800–2600 Ma zircon populations, detritus sourced predominantly from North Africa. In contrast, the c. 950 Ma zircons, which are persistently found in Cambro-Ordovician sediments of North Gondwana, have no obvious African source. We propose that these zircons are sourced from the Rayner Complex–Eastern Ghats regions of Antarctica and India. An Indo-Antarctic source indicates either continental-scale sedimentary transport from central Gondwana to its peripheries or multiple cycles of sediment reworking and redeposition.
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| 27. |
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| 28. |
- Tillberg, Mikael, 1990, et al.
(författare)
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Reconstructing craton-scale tectonic events via in situ Rb-Sr geochronology of poly-phased vein mineralization
- 2021
-
Ingår i: Terra Nova. - : Wiley. - 0954-4879 .- 1365-3121. ; 33:5, s. 502-510
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Tidskriftsartikel (refereegranskat)abstract
- Fault- and fracture-hosted multi-stage mineral assemblages that formed by fracture reactivation and fluid migration, constitute archives of the tectonic evolution of Precambrian cratons. Complex intergrowth patterns of these mineral records often hinder absolute dating of mineralization events for geological models. We apply LA-ICP-MS/MS in situ Rb-Sr dating of single crystal growth zones in sub-mm-wide vein mineralization assemblages including illite, K-feldspar, albite, calcite, mica, zeolites, fluorite and/or epidote at three Palaeoproterozoic crystalline bedrock sites over 300 km apart in the Fennoscandian Shield. The dating campaign reveals multiple age clusters between ca. 1757 +/- 15 and 355 +/- 12 Ma correlating with fluid flow and fracture reactivation events initiated by far-field orogens and their foreland basin evolution. This new approach for reconstructing geological histories of Precambrian cratons connects micro-scale age determinations of different mineral growth zones in fractures with regional-scale crustal dynamic responses to tectonic events.
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| 29. |
- Arenillas, I, et al.
(författare)
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Foraminiferal and δ13C isotopic event-stratigraphy across the Danian–Selandian transition at Zumaya (northern Spain): chronostratigraphic implications
- 2008
-
Ingår i: Terra Nova: the European journal of geosciences. - : Wiley. - 0954-4879. ; 20:1, s. 38-44
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Tidskriftsartikel (refereegranskat)abstract
- The Zumaya section, northern Spain, is a suitable candidate to define the Global Stratotype Section and Point for the base of the Selandian Stage (Palaeocene) because of its excellent accessibility, exposure and stratigraphic continuity. Uncertainties exist, however, with regard to the stratigraphic horizon where to place the Danian/Selandian (D/S) boundary. Five potential stratigraphic horizons (HDS1 to HDS5) to define the D/S boundary have been identified at Zumaya, based on integrated stratigraphic studies that include quantitative planktic and benthic foraminiferal results, as well as delta C-13 isotopic and lithological data. Two of these horizons (HDS2 and HDS4) placed in Zone C26r appear to have particularly good potential for serving as the D/S boundary marker, because they may represent significant global palaeoceanographic, palaeoclimatic and eustatic events.
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| 30. |
- Bergemann, Christian A., et al.
(författare)
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Constraining long-term fault activity in the brittle domain through in situ dating of hydrothermal monazite
- 2018
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Ingår i: Terra Nova. - : Wiley. - 0954-4879. ; 30:6, s. 440-446
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Tidskriftsartikel (refereegranskat)abstract
- Abstract SIMS Th–Pb dating of hydrothermal fissure-vein monazite-(Ce) has the unique potential to date multiple tectonic events under low-grade metamorphic brittle/ductile conditions over large time frames. Monazites-(Ce) from brittle fault systems in the Eastern Alps allow us to constrain their Cretaceous activity over 20 Ma within single crystals, recording all major tectonic events. Eo-Alpine formation of the fluid-filled fissure-veins occurred 90 Ma ago at 352 ± 19°C and 342 ± 42 MPa. This corresponds to peak conditions during regional metamorphism of the Cretaceous collisional nappe stacking. Several stages of dissolution–reprecipitation/recrystallization record fault activity between 84 and 70 Ma. Corresponding fluid inclusions indicate conditions of 229 ± 10°C and 143 ± 20 MPa. This correlates with the formation of sedimentary basins during post-orogenic extension associated with strike-slip movements. The results strengthen the hypothesis that many large fault systems in the Eastern Alps developed during the Cretaceous orogeny and became reactivated during Neogene Alpine tectonics.
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| 31. |
- Eklund, O, et al.
(författare)
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A flow-foliated ignimbrite related to the Aland rapakivi granite in SW Finland
- 1996
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Ingår i: TERRA NOVA. - : BLACKWELL SCIENCE LTD. - 0954-4879. ; 8:6, s. 548-557
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Tidskriftsartikel (övrigt vetenskapligt/konstnärligt)abstract
- A flow-foliated felsic ignimbrite constitutes the uppermost lithological unit of the 1.58 Gyr anorogenic magmatic rocks in SW Finland. The ignimbrite is derived from an explosive eruption of hot (approximate to 950 degrees C) phenocryst-bearing A-type (ra
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| 32. |
- Forsberg, Angelica, et al.
(författare)
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Patients' perceptions of their postoperative recovery for one month
- 2015
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Ingår i: Journal of Clinical Nursing. - : Wiley. - 0962-1067 .- 1365-2702. ; 24:13-14, s. 1825-1836
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Tidskriftsartikel (refereegranskat)abstract
- Aims and objectivesTo explore orthopaedic and general surgery patients' perceptions of their postoperative recovery for one month.BackgroundIn general, nursing research in the postoperative context has been directed towards a single symptom or area, which is valuable. However, there is a lack of studies of orthopaedic and general surgery patients' perceptions of postoperative recovery from a short-term perspective.DesignA quantitative approach with a longitudinal design was used.MethodsA total of 180 patients participated in the study. Data were collected using a standardised questionnaire, the Postoperative Recovery Profile, for self-assessment of recovery. Descriptive statistics reported as proportions were used for the categorical variables. Analytic statistics were used to identify statistically significant differences. Mean values and t-tests were used for quantity variables, and Mann–Whitney U-tests and Chi-squared tests were used for nonparametric variables.ResultsOverall, the orthopaedic patients were substantially less recovered than the general surgery patients. Two-thirds of the orthopaedic patients and half of the general surgery patients perceived severe or moderate pain in the acute recovery phase. Within the general surgery group, there were significant differences in the recovery between the Gastric Bypass patients and colon/ileum surgery patients. The gastric bypass patients were overall more recovered than the other groups of patients. The Gastric Bypass patients reported that they had improved after one month compared to their own status prior to surgery.Conclusions and relevance to clinical practiceNursing support for orthopaedic patients must be improved, especially after they are discharged from the hospital. To structure and monitor individual recovery, a top-five priority profile of the most important problems should be used during follow-up calls after the patient is discharged from the hospital. Postoperative pain continues to represent a clinical problem that requires attention. Heterogeneity in the perceptions of recovery within the general surgery group was indicated, which may depend on the surgical procedure as well as the patients' expectations and comparisons with their lives before surgery. Rather than return to their preoperative levels, certain patients tend to continue towards a new or different life postoperatively.
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| 33. |
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| 34. |
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| 35. |
- Rymer, H., et al.
(författare)
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New mass increase beneath Askja volcano, Iceland – a precursor to renewed activity?
- 2010
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Ingår i: Terra Nova. - 0954-4879. ; 22:4, s. 309-313
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Tidskriftsartikel (refereegranskat)abstract
- Askja is an active central volcano located on the NS trending en echelon rift zone marking the mid-Atlantic plate boundary in North Iceland. Between 2007 and 2009, we observed a gravity increase at the centre of the caldera. This contrasts with net gravity decreases recorded between 1988 and 2007 interpreted previously in terms of magma drainage. The recent gravity increase is rapid, but similar in terms of lateral extent to the preceding decrease. This gravity increase corresponds to a sub-surface mass increase of 0.68 × 1011 kg at about 3 km depth. It is possible that the new gravity increases observed at Askja reflect accumulation of magma beneath the caldera and thus may herald a new phase in the activity of this volcano, which last erupted in 1961.
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| 36. |
- Simkevicius, P, et al.
(författare)
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Jurassic smectite and kaolinite trends of the East European Platform: implications for palaeobathymetry and palaeoclimate
- 2003
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Ingår i: Terra Nova: the European journal of geosciences. - : Wiley. - 0954-4879. ; 15:4, s. 225-229
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Tidskriftsartikel (refereegranskat)abstract
- Clay minerals cannot only give information on sedimentary depositional environment but also the climate regime under which sediment was weathered. The successions of non-marine to marine Middle and Late Jurassic strata of the East European Platform show upwards increasing contents of smectite and decreasing contents of kaolinite. There is also an increasing smectite vs. kaolinite ratio laterally, in a basinward direction within individual formations. Vertical smectite and kaolinite content curves coincide broadly with the Sahagian and Jones eustatic sea-level curve. All this implies differential settling of smaller smectite particles offshore and larger kaolinite particles onshore. Smectite formation, preservation and supply were further enhanced as the eastwards expanding Late Jurassic arid zone of Laurasia influenced weathering conditions in the sediment source areas, to the north and east of the East European Platform.
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| 37. |
- Vallejo, Cristian, et al.
(författare)
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The early interaction between the Caribbean plateau and the NW South American Plate
- 2006
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Ingår i: Terra Nova: the European journal of geosciences. - : Wiley. - 0954-4879. ; 18:4, s. 264-269
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Tidskriftsartikel (refereegranskat)abstract
- The determination of accurate and precise ages for the timing of collision between oceanic plateaus and continental crust requires an understanding of how the indenting and buttressing plates respond to the collision. We present geochronological, thermochronological, geochemical and isotopic analyses of magmatic rocks from the Ecuadorian Andes, which relate to the collision of the Late Cretaceous Caribbean Plateau and Great Arc sequence with NW South America. The cessation of subduction magmatism during 65-64 Ma beneath the eastern edge of Caribbean Plateau was synchronous with accelerated surface uplift and exhumation within the buttressing continental margin during 75-65 Ma. We interpret this as the collision of the leading edge of the Caribbean Plateau and arc sequence with the South American Plate at 75-65 Ma. A U/Pb (zircon) SHRIMP age of 87.10 +/- 1.66 (2 sigma) Ma, yielded by an accreted fragment of the plateau, precludes previous estimates of collision at 85-80 Ma if the plateau erupted above the Galapagos hotspot.
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