Early Proterozoic tectonic style in central Wisconsin

1983 ◽  
pp. 85-96 ◽  
Author(s):  
R. S. Maass
Keyword(s):  
Early Proterozoic ◽  
Tectonic Style

Tectonic style and mechanism of early proterozoic successor basin development, Southern Africa

1988 ◽  
Vol 156 (3-4) ◽  
pp. 275-291 ◽  
Author(s):  
C.W. Clendenin ◽  
E.G. Charlesworth ◽  
S. Maske
Keyword(s):  
Southern Africa ◽  
Early Proterozoic ◽  
Basin Development ◽  
Tectonic Style

Stratigraphy and structure of the Early Proterozoic Wilson Island Group, East Arm thrust-fold belt, N.W.T.

1990 ◽  
Vol 27 (4) ◽  
pp. 552-569 ◽  
Author(s):  
Bradford J. Johnson
Keyword(s):  
Crustal Extension ◽  
Early Proterozoic ◽  
Clastic Rocks ◽  
Marine Sedimentation ◽  
Volcanic Suite ◽  
Island Group ◽  
Regional Tectonic ◽  
Sediment Deformation ◽  
Tectonic Style ◽  
Feldspathic Sandstone

Investigation of the stratigraphy and structure of the 1.9 Ga Wilson Island Group has led to sedimentological and tectonic interpretations that are consistent with models for an Early Proterozoic collision between the Slave and Rae provinces. The lower part of the 8 km thick Wilson Island Group consists of alluvial clastic rocks and a bimodal volcanic suite. These are overlain by mixed siliciclastic and carbonate rocks that are inferred as representing a combination of alluvial and shallow-marine sedimentation. Finally, an upward-fining succession of feldspathic sandstone, ironstone, and mudstone records progradation of an alluvial system followed by a major transgression. Soft-sediment deformation structures, intrabasinal coarse detritus, and abrupt vertical facies changes collectively indicate that the early stages of deposition were tectonically controlled.Regional penetrative foliations and a steeply plunging stretching lineation reflect deformation concomitant with greenschist-facies to lower amphibolite-facies metamorphism. Open to tight, plunging, northwesterly overturned folds formed synchronously with axial-plane cleavage in quartzites and deformed an older cleavage in pelites. These synmetamorphic structures were refolded by postmetamorphic kinks and dissected by transcurrent and normal faults.The Wilson Island Group evolved during postcollisional convergence, when thrusting and dextral transcurrent shearing characterized the regional tectonic style. However, the bimodal volcanic suite indicates a component of crustal extension that, in the regional context, favours a pull-apart-basin origin for the Wilson Island Group.

The first data on possible Mezozoic magmatism within the Western slope of the Southern Urals

2018 ◽  
pp. 24-34
Author(s):  
A. O. Khotylev ◽  
N. B. Devisheva ◽  
Al. V. Tevelev ◽  
V. M. Moseichuk
Keyword(s):  
Southern Urals ◽  
Western Slope ◽  
Isotopic Age ◽  
The Southern Urals ◽  
Early Proterozoic ◽  
Carbonate Formations ◽  
Two Bodies

Within the Western slope of the Southern Urals, there are plenty of basite dyke complexes of Riphean to Vendian among Precambrian terrigenous-carbonate formations. In metamorphic formations of the Taratash complex (Archean to Early Proterozoic, the northern closure of the Bashkirian meganticlinorium) there was observed the andesitic dyke with isotopic age of 71±1 Ma (U-Pb SHRIMP II on zircons) and near Bakal two bodies of gabbroids with zircons of similar ages were found. These are the first evidence of possible Mezozoic magmatism in this region.

The Archaean Atâ intrusive complex (Atâ tonalite), north-east Disko Bugt, West Greenland

1999 ◽  
pp. 103-112
Author(s):  
Feiko Kalsbeek ◽  
Lilian Skjernaa
Keyword(s):  
Intrusive Complex ◽  
The South ◽  
Original Series ◽  
Early Proterozoic ◽  
West Greenland ◽  
North East ◽  
The North ◽  
Southern Border ◽  
Area North ◽  
Igneous Layering

NOTE: This article was published in a former series of GEUS Bulletin. Please use the original series name when citing this article, for example: Kalsbeek, F., & Skjernaa, L. (1999). The Archaean Atâ intrusive complex (Atâ tonalite), north-east Disko Bugt, West Greenland. Geology of Greenland Survey Bulletin, 181, 103-112. https://doi.org/10.34194/ggub.v181.5118 _______________ The 2800 Ma Atâ intrusive complex (elsewhere referred to as ‘Atâ granite’ or ‘Atâ tonalite’), which occupies an area of c. 400 km2 in the area north-east of Disko Bugt, was emplaced into grey migmatitic gneisses and supracrustal rocks. At its southern border the Atâ complex is cut by younger granites. The complex is divided by a belt of supracrustal rocks into a western, mainly tonalitic part, and an eastern part consisting mainly of granodiorite and trondhjemite. The ‘eastern complex’ is a classical pluton. It is little deformed in its central part, displaying well-preserved igneous layering and local orbicular textures. Near its intrusive contact with the overlying supracrustal rocks the rocks become foliated, with foliation parallel to the contact. The Atâ intrusive complex has escaped much of the later Archaean and early Proterozoic deformation and metamorphism that characterises the gneisses to the north and to the south; it belongs to the best-preserved Archaean tonalite-trondhjemite-granodiorite intrusions in Greenland.

Sign in / Sign up

Export Citation Format

Share Document