Contribution a l'etude tectonique de la presqu'ile de Brogger (Spitsberg)

1966 ◽  
Vol S7-VIII (4) ◽  
pp. 560-566 ◽  
Author(s):  
Lucien Barbaroux
Keyword(s):  
Late Carboniferous ◽  
Late Paleozoic ◽  
Metamorphic Complex

Abstract New observations on the Brogger peninsula (Spitsbergen) show that the Hecla Hoek (Caledonide) geosynclinal metamorphic complex, reactivated by successive orogenies, overlaps Paleozoic and Cenozoic sedimentary formations in a northwest direction along a continuous front. The role of northwest-southeast-trending deformation in the Hercynian (late Paleozoic) and north-south deformation in the Tertiary assume greater importance than was heretofore accorded them. The existence of an Erzgebirgian (late Carboniferous) and a Saalian (mid-Permian) phase of Paleozoic orogeny can be shown.

Evidence of oribatid mite detritivory in Antarctica during the late Paleozoic and Mesozoic

2004 ◽  
Vol 78 (6) ◽  
pp. 1146-1153 ◽  
Author(s):  
Derek W. Kellogg ◽  
Edith L. Taylor
Keyword(s):  
Fossil Record ◽  
Oribatid Mite ◽  
Late Paleozoic ◽  
Transantarctic Mountains ◽  
Animal Interaction ◽  
Wood Boring

Despite their importance in breaking down lignified tissue today, much is still unknown about the role of mites in the fossil record, especially with reference to the Paleozoic–Mesozoic transition. This study examines permineralized peat from three localities in the central Transantarctic Mountains, ranging in age from Permian to Jurassic, for evidence of diversity and abundance of wood-boring mites. Evidence of mites, in the form of coprolites and tunnels in wood and other tissues, was found at all three localities; the Triassic site included more than 10 times as many wood borings as the Permian site. Our results supplement prior evidence of wood-boring mites during the Mesozoic and thereby fill in the known geologic range of this plant/animal interaction.

scholarly journals Influence of temporally varying weatherability on CO<sub>2</sub>–climate coupling and ecosystem change in the late Paleozoic

2020 ◽  
Author(s):  
Jon D. Richey ◽  
Isabel P. Montañez ◽  
Yves Goddéris ◽  
Cindy V. Looy ◽  
Neil P. Griffis ◽  
...  
Keyword(s):  
Steady State ◽  
Ice Age ◽  
Secular Change ◽  
Ecosystem Change ◽  
Late Paleozoic ◽  
Relative Role ◽  
C Cycle ◽  
Ecosystem Perturbation ◽  
Atmospheric Pco2

Abstract. Earth's penultimate icehouse, the Late Paleozoic Ice Age (LPIA), was a time of dynamic glaciation and repeated ecosystem perturbation, under conditions of substantial variability in atmospheric pCO2 and O2. Improved constraints on the evolution of atmospheric pCO2 and O2 : CO2 during the LPIA and its subsequent demise to permanent greenhouse conditions is crucial for better understanding the nature of linkages between atmospheric composition, climate, and ecosystem perturbation during this time. We present a new and age-recalibrated pCO2 reconstruction for a 40-Myr interval (~313 to 273 Ma) of the late Paleozoic that (1) confirms a previously hypothesized strong CO2-glaciation linkage, (2) documents synchroneity between major pCO2 and O2 : CO2 changes and compositional turnovers in terrestrial and marine ecosystems, (3) lends support for a modeled progressive decrease in the CO2 threshold for initiation of continental ice sheets during the LPIA, and (4) indicates a likely role of CO2 and O2 : CO2 thresholds in floral ecologic turnovers. Modeling of the relative role of CO2 sinks and sources, active during the LPIA and its demise, on steady-state pCO2 using an intermediate complexity climate-C cycle model (GEOCLIM) and comparison to the new multi-proxy CO2 record provides new insight into the relative influences of the uplift of the Central Pangaean Mountains, intensifying aridification, and increasing mafic rock to-granite rock ratio of outcropping rocks on the global efficiency of CO2 consumption and secular change in steady-state pCO2 through the late Paleozoic.

scholarly journals Geochemistry of trace elements in rock-forming minerals of gneisses and granites of the Murzinka granite area, Central Urals

2020 ◽  
pp. 74-88
Author(s):  
S.V. Pribavkin ◽  
N.S. Borodina ◽  
M.V. Chervyakovskaya
Keyword(s):  
Trace Elements ◽  
Trace Element Composition ◽  
Element Composition ◽  
Metamorphic Complex ◽  
Granite Pluton ◽  
Formation Conditions ◽  
Granite Magmatism ◽  
Central Urals ◽  
Distribution Of Trace Elements

The Murzinka granite area (Central Urals), which combines Murzinka granite pluton and underlying rocks of the Murzinka-Adui metamorphic complex, exhibits an evident wetrending geochemical zonation of magmatism with increasing of Rb, Li, Nb and Ta contents and decreasing ba and Sr contents and K/Rb, zr/Hf and Nb/Ta ratios from vein granites of the Yuzhakovo complex to granites of the Vatikha complex and further to granites of the Murzinka complex (Fershtater et al., 2019). To develop the ideas about geochemical zonation of the Murzinka granite magmatism, as well as about the role of gneisses of the Murzinka-Adui metamorphic complex in the formation of granites, we studied the distribution of trace elements in biotite and feldspars of gneisses and granites. Biotite shows an increase in Li, Rb, Cs, Nb, Ga, zn, Mn, Sc, Sn and Tl contents and a decrease in V, Cr, Co, Ni, Y, zr and ba contents from vein biotites of the Yuzhakovo granites to two-mica granites of the Murzinka complex. The composition of feldspars also changes in this direction: plagioclase is enriched in Li, Rb, Cs, be, zn and depleted in Sr, ba, Ga and Pb and K-feldspar is enriched in Rb and depleted in Sr and ba. The varying trace element composition of rock-forming minerals of gneisses and granites is explained by We-trending change in the composition of a crustal protolith, as well as the formation conditions of granites. Figures 6. Tables 4. References 17.

scholarly journals Late Carboniferous dextral transpressional reactivation of the crustal-scale Walls Boundary Fault, Shetland: the role of pre-existing structures and lithological heterogeneities

2020 ◽  
Vol 178 (1) ◽  
pp. jgs2020-078
Author(s):  
Timothy B. Armitage ◽  
Lee M. Watts ◽  
Robert E. Holdsworth ◽  
Robin A. Strachan
Keyword(s):  
Late Carboniferous ◽  
Strain Partitioning ◽  
Boundary Fault ◽  
Existing Structures ◽  
Tectonic Events ◽  
Tectonic Environment ◽  
Western Side ◽  
East West ◽  
Lithological Heterogeneity

The Walls Boundary Fault in Shetland, Scotland, formed during the Ordovician–Devonian Caledonian orogeny and underwent dextral reactivation in the Late Carboniferous. In a well-exposed section at Ollaberry, westerly verging, gently plunging regional folds in the Neoproterozoic Queyfirth Group on the western side of the Walls Boundary Fault are overprinted by faults and steeply plunging Z-shaped brittle–ductile folds that indicate contemporaneous right-lateral and top-to-the-west reverse displacement. East of the Walls Boundary Fault, the Early Silurian Graven granodiorite complex exhibits fault-parallel fractures with Riedel, P and conjugate shears indicating north–south-striking dextral deformation and an additional contemporaneous component of east–west shortening. In the Queyfirth Group, the structures are arranged in geometrically and kinematically distinct fault-bounded domains that are interpreted to result from two superimposed tectonic events, the youngest of which displays evidence for bulk dextral transpressional strain partitioning into end-member wrench and contractional strain domains. During dextral transpressional deformation, strain was focused into pelite horizons and favourably aligned pre-existing structures, leaving relicts of older deformation in more competent lithologies. This study highlights the importance of pre-existing structures and lithological heterogeneity during reactivation and suggests the development of a regional transpressional tectonic environment during the Late Carboniferous on the Shetland Platform.

Geophysical study of basement fractures on the western European and eastern Canadian shelves: transatlantic correlations, and late Hercynian movements

1978 ◽  
Vol 15 (3) ◽  
pp. 397-404 ◽  
Author(s):  
J. P. Lefort ◽  
R. T. Haworth
Keyword(s):  
New England ◽  
Late Carboniferous ◽  
Late Paleozoic ◽  
Stress System ◽  
Northern Spain ◽  
Geological Interpretation ◽  
The Third ◽  
The North ◽  
Geophysical Study ◽  
Western European

Geological interpretation of geophysical data (magnetic, gravimetric and seismic) on the western European and eastern Canadian shelves indicates a transatlantic correlation between the major late Paleozoic fractures of those areas.East–west megafractures, which are primarily grouped in two latitudinal belts at 44° N and 48° N, are the most obvious and correlative. The first zone of fractures was an extension of the South Armorican shear zone, which continued to the north of Flemish Cap. The second was an eastwards extension of the Cobequid–Chedabucto–Scatarie Fault, which crossed Galicia Bank, northern Spain and southern France. A third zone possibly existed between the Clinton–Newbury Fault of New England and mid-Spain, Corsica and Sardinia (when they are moved back to their late Paleozoic positions). The location of the shortening trajectories shows that the first two zones (and perhaps the third one) belonged to the same stress system during late Carboniferous. As a hypothesis, different rates of displacement between 'peri-Atlantic' plates during their northward movement in Late Carboniferous time could be the source of the stress.

scholarly journals Neoproterozoic and post-Caledonian exhumation and shallow faulting in NW Finnmark from K–Ar dating and <i>p</i>∕<i>T</i> analysis of fault rocks

Solid Earth ◽  
2018 ◽  
Vol 9 (4) ◽  
pp. 923-951 ◽  
Author(s):  
Jean-Baptiste P. Koehl ◽  
Steffen G. Bergh ◽  
Klaus Wemmer
Keyword(s):  
Early Carboniferous ◽  
Late Carboniferous ◽  
Late Paleozoic ◽  
Normal Faults ◽  
Fault Rock ◽  
Fault Rocks ◽  
Basement Rocks ◽  
Iapetus Ocean ◽  
Tectonic Window ◽  
Brittle Faulting

Abstract. Well-preserved fault gouge along brittle faults in Paleoproterozoic, volcano-sedimentary rocks of the Raipas Supergroup exposed in the Alta–Kvænangen tectonic window in northern Norway yielded latest Mesoproterozoic (approximately 1050 ± 15 Ma) to mid-Neoproterozoic (approximately 825–810 ± 18 Ma) K–Ar ages. Pressure–temperature estimates from microtextural and mineralogy analyses of fault rocks indicate that brittle faulting may have initiated at a depth of 5–10 km during the opening of the Asgard Sea in the latest Mesoproterozoic–early Neoproterozoic (approximately 1050–945 Ma) and continued with a phase of shallow faulting to the opening of the Iapetus Ocean–Ægir Sea and the initial breakup of Rodinia in the mid-Neoproterozoic (approximately 825–810 Ma). The predominance and preservation of synkinematic smectite and subsidiary illite in cohesive and non-cohesive fault rocks indicate that Paleoproterozoic basement rocks of the Alta–Kvænangen tectonic window remained at shallow crustal levels (< 3.5 km) and were not reactivated since mid-Neoproterozoic times. Slow exhumation rate estimates for the early–mid-Neoproterozoic (approximately 10–75 m Myr−1) suggest a period of tectonic quiescence between the opening of the Asgard Sea and the breakup of Rodinia. In the Paleozoic, basement rocks in NW Finnmark were overthrusted by Caledonian nappes along low-angle thrust detachments during the closing of the Iapetus Ocean–Ægir Sea. K–Ar dating of non-cohesive fault rocks and microtexture mineralogy of cohesive fault rock truncating Caledonian nappe units show that brittle (reverse) faulting potentially initiated along low-angle Caledonian thrusts during the latest stages of the Caledonian Orogeny in the Silurian (approximately 425 Ma) and was accompanied by epidote–chlorite-rich, stilpnomelane-bearing cataclasite (type 1) indicative of a faulting depth of 10–16 km. Caledonian thrusts were inverted (e.g., Talvik fault) and later truncated by high-angle normal faults (e.g., Langfjorden–Vargsundet fault) during subsequent, late Paleozoic, collapse-related widespread extension in the Late Devonian–early Carboniferous (approximately 375–325 Ma). This faulting period was accompanied by quartz- (type 2), calcite- (type 3) and laumontite-rich cataclasites (type 4), whose cross-cutting relationships indicate a progressive exhumation of Caledonian rocks to zeolite-facies conditions (i.e., depth of 2–8 km). An ultimate period of minor faulting occurred in the late Carboniferous–mid-Permian (315–265 Ma) and exhumed Caledonian rocks to shallow depth at 1–3.5 km. Alternatively, late Carboniferous (?) to early–mid-Permian K–Ar ages may reflect late Paleozoic weathering of the margin. Exhumation rates estimates indicate rapid Silurian–early Carboniferous exhumation and slow exhumation in the late Carboniferous–mid-Permian, supporting decreasing faulting activity from the mid-Carboniferous. NW Finnmark remained tectonically quiet in the Mesozoic–Cenozoic.

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