scholarly journals Paleomagnetism of Permian-Triassic volcanic sequences from Son La province, northwest Vietnam

2021 ◽  
Vol 43 (2) ◽  
pp. 220-235
Author(s):  
Cung Thuong Chi ◽  
John W. Geissman ◽  
Taylor Borgfeldt ◽  
Nguyen Hoang
Keyword(s):  
Remanent Magnetization ◽  
Volcanic Rocks ◽  
Lower Triassic ◽  
Upper Permian ◽  
Late Permian ◽  
Virtual Geomagnetic Pole ◽  
Geomagnetic Pole ◽  
Orogenic Belts ◽  
Coherent Part ◽  
Paleomagnetic Direction

Nineteen sites with 198 oriented-core samples have been collected from the Upper Permian-Lower Triassic volcanic rocks of Vien Nam Formation at Quynh Nhai locality, Son La Province, northwestern Vietnam. The characteristic remanent magnetization components carried by magnetite and hematite were successfully isolated from secondary components reveal a mean paleomagnetic direction Ds = 48.3°, Is = -10.0°, a95 = 8.0°, corresponding to a virtual geomagnetic pole located at l = 35.7°N, f = 217.4°E and a paleo-latitude of study area situated at 5.1°S during the Permian time. Compared with the Late Permian-Early Triassic pole of the South China Block (SCB), the data show that crustal elements of NW Vietnam have been close to, but not unequivocally a coherent part of the SCB, since the Late Permian. Development of the parallel NW-SE striking Song Ma and Song Chay orogenic belts did not involve the closure of wide (> 500 km) ocean basins.

scholarly journals Paleomagnetism of Permian-Triassic volcanic sequences from Son La province, northwest Vietnam

2021 ◽  
Vol 43 (2) ◽  
Author(s):  
Cung Thuong Chi ◽  
John W. Geissman ◽  
Taylor Borgfeldt ◽  
Nguyen Hoang
Keyword(s):  
Remanent Magnetization ◽  
Volcanic Rocks ◽  
Lower Triassic ◽  
Upper Permian ◽  
Late Permian ◽  
Virtual Geomagnetic Pole ◽  
Geomagnetic Pole ◽  
Orogenic Belts ◽  
Coherent Part ◽  
Paleomagnetic Direction

Nineteen sites with 198 oriented-core samples have been collected from the Upper Permian-Lower Triassic volcanic rocks of Vien Nam Formation at Quynh Nhai locality, Son La Province, northwestern Vietnam. The characteristic remanent magnetization components carried by magnetite and hematite were successfully isolated from secondary components reveal a mean paleomagnetic direction Ds = 48.3°, Is = -10.0°, a95 = 8.0°, corresponding to a virtual geomagnetic pole located at l = 35.7°N, f = 217.4°E and a paleo-latitude of study area situated at 5.1°S during the Permian time. Compared with the Late Permian-Early Triassic pole of the South China Block (SCB), the data show that crustal elements of NW Vietnam have been close to, but not unequivocally a coherent part of the SCB, since the Late Permian. Development of the parallel NW-SE striking Song Ma and Song Chay orogenic belts did not involve the closure of wide (> 500 km) ocean basins.

scholarly journals Intermediate Field Directions Recorded in Pliocene Basalts in Styria (Austria): Evidence for Cryptochron C2r.2r-1

2021 ◽  
Author(s):  
Elisabeth Schnepp ◽  
Patrick Arneitz ◽  
Morgan Ganerød ◽  
Robert Scholger ◽  
Ingomar Fritz ◽  
...  
Keyword(s):  
Dipole Moments ◽  
Volcanic Rocks ◽  
Field Configuration ◽  
Volcanic Complex ◽  
Virtual Geomagnetic Pole ◽  
Magnetic Carriers ◽  
Size Characteristic ◽  
Geomagnetic Pole ◽  
Regional Tectonic ◽  
Geomagnetic Polarity

Abstract Pliocene volcanic rocks from South-East-Austria were paleomagnetically investigated. Samples were taken from 28 sites located on eight different volcanoes. Rock magnetic investigations revealed that magnetic carriers are Ti-rich or Ti-poor titanomagnetites with mainly pseudo-single-domain grain size. Characteristic remanent magnetization directions were obtained from alternating field as well as from thermal demagnetization. Four localities give reversed directions agreeing with the expected direction from secular variation. Another four localities of the Klöch-Königsberg volcanic complex (3) and the Neuhaus volcano (1) have reversed directions with shallow inclinations and declinations of about 240° while the locality Steinberg yields a positive inclination of about 30° and 200° declination. These aberrant directions cannot be explained by local or regional tectonic movements. All virtual geomagnetic pole positions are located on the southern hemisphere. Four virtual geomagnetic poles lie close to the geographic pole, while all others are concentrated in a narrow longitude sector offshore South America (310° to 355°) with low virtual geomagnetic pole latitudes ranging from − 15° to -70°. The hypothesis that a transitional geomagnetic field configuration was recorded during the short volcanic activity of these five localities is supported by 9 paleointensity results and 39Ar/40Ar dating. Virtual geomagnetic dipole moments range from 1.1 to 2.9·1022 Am2 for sites with low VGP latitudes about 60° and from 3.0 to 9.3·1022 Am2 for sites with higher virtual geomagnetic pole latitudes. The new 39Ar/40Ar ages of 2.51 ± 0.27 Ma for Klöch and 2.39 ± 0.03 Ma for Steinberg allow for the correlation of the Styrian transitional directions with cryptochron C2r.2r-1 of the geomagnetic polarity time scale.

First basal synapsids (“pelycosaurs”) from the Upper Permian-?Lower Triassic of Uruguay, South America

2003 ◽  
Vol 77 (2) ◽  
pp. 389-392 ◽  
Author(s):  
Graciela Piñeiro ◽  
Mariano Verde ◽  
Martín Ubilla ◽  
Jorge Ferigolo
Keyword(s):  
South Africa ◽  
North America ◽  
South America ◽  
Lower Triassic ◽  
Late Carboniferous ◽  
Upper Permian ◽  
Lower Permian ◽  
Late Permian ◽  
Early Permian ◽  
Continental Deposits

In their monograph Review of the Pelycosauria, Romer and Price (1940), proposed that the earliest synapsids (“pelycosaurs”) were cosmopolitan, despite the observation that amniotes appeared to be restricted to the paleotropics during the Late Carboniferous and Early Permian (290–282 Ma). Romer and Price (1940) accounted for the scarcity of terrestrial tetrapods, including “pelycosaurs,” in Lower Permian beds elsewhere to the absence of coeval continental deposits beyond North America and Europe. Indeed, most workers recognized a geographical and temporal gap between Permo-Carboniferous “pelycosaurs” and therapsid synapsids. Recent research has confirmed that varanopid and caseid “pelycosaurs” were components of therapsid-dominated Late Permian faunas preserved in Russia and South-Africa (Tatarinov and Eremina, 1975; Reisz, 1986; Reisz et al., 1998; Reisz and Berman, 2001).

Paléomagnetisme de la formation des 'grès-à-Voltzia' (Buntsandstein supérieur) du Massif des Vosges (France)

1977 ◽  
Vol 14 (7) ◽  
pp. 1490-1514 ◽  
Author(s):  
Daniel Biquand
Keyword(s):  
Thermal Treatment ◽  
Lower Triassic ◽  
Physical Treatment ◽  
Virtual Geomagnetic Pole ◽  
Null Field ◽  
Geomagnetic Pole ◽  
Long Time ◽  
Sandstone Formation ◽  
Alternative Field ◽  
Grès À Voltzia

The results of a paleomagnetic study of 99 samples (156 specimens) from 6 quarries spread over an area of 6000 km2 in the Lower Triassic Voltzia sandstone formation from the Vosges (France) are presented. More precisely, this paper is limited to a detailed statistical study of magnetization directions at different stages of physical treatment of the magnetized material: exposure in null field for long time periods, up to 18 months; attack with moderate alternative fields (600 Oe (4.8 × 104 A/m) eff. maximum), then strong fields (1600 Oe (12.7 × 104 A/m) eff.); thermal treatment to 670 °C.Here is a summary of the results:(1) Strong alternative field attack or moderate thermal treatment (≤400 °C) do not result in the acquisition of parasitic magnetization, however weak, of preferred orientation, but seem to cause a random scatter of magnetization directions.(2) Thermal treatment seems preferable to alternative field attack to completely destroy secondary magnetization, ubiquitous and intense, the direction of which is close to the present terrestrial field direction.(3) Primary magnetization usually shows inverse polarity. The coordinates of the corresponding virtual geomagnetic pole are: 43.1° N, 145.7° E; Dm = 4.9°; Dp = 2.5°.(4) This study allowed the testing of the validity of secondary magnetization cancellation method by vectorial calculus techniques using the two primary magnetization polarities obtained after long exposure in null field. [Journal Translation]

Paleomagnetism of Archean rocks from northwestern Ontario: Wabigoon gabbro, Wabigoon Subprovince

1983 ◽  
Vol 20 (12) ◽  
pp. 1805-1817 ◽  
Author(s):  
David J. Dunlop
Keyword(s):  
Remanent Magnetization ◽  
Natural Remanent Magnetization ◽  
Blocking Temperature ◽  
Virtual Geomagnetic Pole ◽  
Polar Wander ◽  
Apparent Polar Wander Path ◽  
Northwestern Ontario ◽  
Paleomagnetic Pole ◽  
Geomagnetic Pole ◽  
Chemical Remanent Magnetization

The Wabigoon gabbro of the Archean Wabigoon greenstone belt in northwestern Ontario preserves a univectorial natural remanent magnetization (NRM) with D = 246°, I = 12° (k = 19.5, α95 = 10.5°, N = 11 sites). The precision is reduced if sample means are averaged, however (k = 9.3, α95 = 9.2°, N = 29 samples). The paleomagnetic pole falls either at 160°W, 11°S (δp = 5.3°, δm = 10.6°), corresponding to an age of ~1300 Ma on the Laurentian apparent polar wander path, or the reverse of this, 20°E, 11° N, corresponding to a late Archean age (~2800 Ma). No ~1300 Ma igneous or metamorphic event is known in the area; a major west-northwest-trending dike about 9 km south of the gabbro yields a virtual geomagnetic pole at 122°W, 45°N and seems to be of Abitibi age (~2150 Ma) rather than Mackenzie age (~1250 Ma). A few gabbro samples and some greenstones from the intrusive baked zone have hybrid remanences in which a higher blocking temperature Kenoran-age (~2600 Ma) NRM is superimposed on the gabbro characteristic NRM. However, the Kenoran component may be a younger chemical remanent magnetization (CRM) residing in hematite. The hypothesis that the gabbro characteristic remanence is itself a hybrid of Kenoran and Keweenawan (~1100 Ma) NRM's, which would explain both the high between-sample scatter and the lack of a ~1300 Ma remagnetizing event, is considered but rejected because fewer than 10% of the gabbro samples exhibit multivectorial swings during alternating field or thermal cleaning. Two geomagnetic field reversals are recorded at interior sites, but only one or none is recorded near the margin of the intrusion. The different cooling histories of margin and interior, as well as the bulk of the other evidence, favour magnetization during initial cooling in late Archean time.

scholarly journals Intermediate field directions recorded in Pliocene basalts in Styria (Austria): evidence for cryptochron C2r.2r-1

2021 ◽  
Vol 73 (1) ◽  
Author(s):  
Elisabeth Schnepp ◽  
Patrick Arneitz ◽  
Morgan Ganerød ◽  
Robert Scholger ◽  
Ingomar Fritz ◽  
...  
Keyword(s):  
Dipole Moments ◽  
Volcanic Rocks ◽  
Field Configuration ◽  
Volcanic Complex ◽  
Virtual Geomagnetic Pole ◽  
Magnetic Carriers ◽  
Geomagnetic Pole ◽  
Regional Tectonic ◽  
Geomagnetic Polarity ◽  
Geomagnetic Polarity Time Scale

AbstractPliocene volcanic rocks from south-east Austria were paleomagnetically investigated. Samples were taken from 28 sites located on eight different volcanoes. Rock magnetic investigations revealed that magnetic carriers are Ti-rich or Ti-poor titanomagnetites with mainly pseudo-single-domain characteristics. Characteristic remanent magnetization directions were obtained from alternating field as well as from thermal demagnetization. Four localities give reversed directions agreeing with the expected direction from secular variation. Another four localities of the Klöch–Königsberg volcanic complex (3) and the Neuhaus volcano (1) have reversed directions with shallow inclinations and declinations of about 240° while the locality Steinberg yields a positive inclination of about 30° and 200° declination. These aberrant directions cannot be explained by local or regional tectonic movements. All virtual geomagnetic pole positions are located on the southern hemisphere. Four virtual geomagnetic poles lie close to the geographic pole, while all others are concentrated in a narrow longitude sector offshore South America (310°–355°) with low virtual geomagnetic pole latitudes ranging from − 15° to − 70°. The hypothesis that a transitional geomagnetic field configuration was recorded during the short volcanic activity of these five localities is supported by 9 paleointensity results and 39Ar/40Ar dating. Virtual geomagnetic dipole moments range from 1.1 to 2.9·1022 Am2 for sites with low VGP latitudes below about 60° and from 3.0 to 9.3·1022 Am2 for sites with higher virtual geomagnetic pole latitudes. The new 39Ar/40Ar ages of 2.51 ± 0.27 Ma for Klöch and 2.39 ± 0.03 Ma for Steinberg allow for the correlation of the Styrian transitional directions with cryptochron C2r.2r-1 of the geomagnetic polarity time scale. Graphic abstract

scholarly journals New biostratigraphic evidence of Late Permian to Late Triassic deposits from Central Tibet and their paleogeographic implications

Lithosphere ◽  
2019 ◽  
Vol 11 (5) ◽  
pp. 683-696 ◽  
Author(s):  
Gui-chun Wu ◽  
Zhan-sheng Ji ◽  
Wei-hua Liao ◽  
Jian-xin Yao
Keyword(s):  
Middle Triassic ◽  
Carbonate Platform ◽  
Lower Triassic ◽  
Upper Triassic ◽  
Suture Zone ◽  
Late Triassic ◽  
Upper Permian ◽  
Early Triassic ◽  
Late Permian ◽  
The North

Abstract Triassic deposits in the Bangong-Nujiang Suture Zone are important for understanding its tectonic nature and evolutionary history, but have not been systematically studied due to a lack of biostratigraphic data. For a long time, the Upper Triassic Quehala Group featuring clasolite has been regarded as the only rocky unit. In recent years, the silicite-dominated Gajia Formation that bears radiolarian fossils was suggested to represent Ladinian to Carnian deposits. The Upper Permian and Lower Triassic rocks have never been excavated and thus are considered to be absent. This research, however, reveals that fossils aged from the Late Permian to Anisian of the Middle Triassic and Norian of the Late Triassic have been preserved in the central Bangong-Nujiang Suture Zone, which provides evidence of Upper Permian to early Middle Triassic deposits and provides new insights on the Upper Triassic strata as well. A new Triassic strata succession is thus proposed for the Bangong-Nujiang Suture Zone, and it demonstrates great similarities with those from Lhasa to the south and Qiangtang to the north. Therefore, we deduce that the Bangong-Nujiang Suture Zone was under a similar depositional setting as its two adjacent terranes, and it was likely a carbonate platform background because limestones were predominant across the Triassic. The newly acquired biostratigraphic data indicate that Lhasa and Qiangtang could not have been located on two separate continents with disparate sedimentary settings; therefore, the Bangong-Nujiang Suture Zone likely did not represent a large ocean between them. This conclusion is supported by lithostratigraphic and paleomagnetic research, which revealed that Lhasa and Qiangtang were positioned at low to middle latitudes during the Early Triassic. Combining this conclusion with fossil evidence, we suggest that the three main Tibetan terranes were in the same palaeobiogeographic division with South China, at least during the Latest Permian to Early Triassic. The Early Triassic conodont species Pachycladina obliqua is probably a fossil sign of middle to low latitudes in palaeogeography.

Late Permian carbonate concretions in the marine siliciclastic sediments of the Ravnefjeld Formation, East Greenland

2002 ◽  
pp. 126-132
Author(s):  
Jesper Kresten Nielsen ◽  
Nils-Martin Hanken
Keyword(s):  
Mineral Resources ◽  
Sedimentary Basins ◽  
Sedimentary Facies ◽  
Carbonate Reservoir ◽  
Upper Permian ◽  
Late Permian ◽  
East Greenland ◽  
Reservoir Rocks ◽  
Carbonate Concretions ◽  
Siliciclastic Sediments

NOTE: This article was published in a former series of GEUS Bulletin. Please use the original series name when citing this article, for example: Kresten Nielsen, J., & Hanken, N.-M. (2002). Late Permian carbonate concretions in the marine siliciclastic sediments of the Ravnefjeld Formation, East Greenland. Geology of Greenland Survey Bulletin, 191, 126-132. https://doi.org/10.34194/ggub.v191.5140 _______________ This investigation of carbonate concretions from the Late Permian Ravnefjeld Formation in East Greenland forms part of the multi-disciplinary research project Resources of the sedimentary basins of North and East Greenland (TUPOLAR; Stemmerik et al. 1996, 1999). The TUPOLAR project focuses on investigations and evaluation of potential hydrocarbon and mineral resources of the Upper Permian – Mesozoic sedimentary basins. In this context, the Upper Permian Ravnefjeld Formation occupies a pivotal position because it contains local mineralisations and has source rock potential for hydrocarbons adjacent to potential carbonate reservoir rocks of the partly time-equivalent Wegener Halvø Formation (Harpøth et al. 1986; Surlyk et al. 1986; Stemmerik et al. 1998; Pedersen & Stendal 2000). A better understanding of the sedimentary facies and diagenesis of the Ravnefjeld Formation is therefore crucial for an evaluation of the economic potential of East Greenland.

scholarly journals Paleomagnetic study of basaltic rocks from Baengnyeong Island, Korea: efficiency of the Tsunakawa–Shaw paleointensity determination on non-SD-bearing materials and implication for the early Pliocene geomagnetic field intensity

2019 ◽  
Vol 71 (1) ◽  
Author(s):  
Hyeon-Seon Ahn ◽  
Yuhji Yamamoto
Keyword(s):  
Dipole Moment ◽  
Mean Value ◽  
Good Precision ◽  
Dipole Strength ◽  
Virtual Geomagnetic Pole ◽  
Early Pliocene ◽  
Basaltic Rocks ◽  
Geomagnetic Pole ◽  
Bearing Materials ◽  
Fitting In

AbstractFinding the statistical intensity signatures of the Earth’s magnetic field over geologic time has helped understanding of the evolution of the Earth’s interior and its interactions with other integral parts of Earth systems. However, this has been often hampered by a paucity of absolute paleointensity (API) data, which are difficult to obtain primarily because of non-ideal magnetic behaviors of natural materials. Here, we present new API determination data with paleodirectional and rock magnetic analyses from basaltic rocks probably aged ~ 4‒5 Ma in Baengnyeong Island, Korea. Paleodirectional analysis obtained an overall mean direction of D = 347.3° and I = 38.3° (α95 = 4.9°, k = 113.4) corresponding to a virtual geomagnetic pole at 342.1° E and 70.2° N. Comprehensive rock magnetic analyses identified Ti-poor titanomagnetite with, in part, multi-domain (MD) particles as a main carrier of remanent magnetization. The Tsunakawa–Shaw (TS) method yielded 12 qualified API estimates with a high success rate, efficiently removing possible MD influences, and resulted in a mean value of 13.1 μT with good precision (1.7 μT, standard deviation). The Thellier method of the IZZI protocol with pTRM checks, coupled with the use of a bootstrap approach instead of the “conventional best-fitting” in API determination, gave 6.6‒19.7 μT as a 95% confidence interval of its mean API estimate, which supports the reliability of our TS-derived API mean estimate; but it is not considered in the final mean value because of the relatively large uncertainty. The virtual dipole moment corresponding to the TS-derived API mean, 2.9 (± 0.4) × 1022 Am2, is somewhat lower than the expectations of the past few Myr averages. Combined with a global API database, our new data implies a larger dispersion in the dipole moment during the early Pliocene than previously inferred. This also suggests that the issue of whether the early Pliocene average dipole strength was moderately high (> 5 × 1022 Am2) or consistent (4‒5 × 1022 Am2) should be discussed further.

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