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

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

Download Full-text

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

10.21203/rs.3.rs-408695/v1 ◽

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.

Download Full-text

Palaeodirectional and palaeointensity results of Paleocene and Eocene basalts from West Greenland

Bulletin of the Geological Society of Denmark ◽

10.37570/bgsd-1999-46-07 ◽

1999 ◽

Vol 46 ◽

pp. 69-78

Author(s):

Janna Riisager ◽

Mireille Perrin

Keyword(s):

High Temperature ◽

Remanent Magnetization ◽

Dipole Moments ◽

Early Eocene ◽

Flood Basalts ◽

West Greenland ◽

Three Samples ◽

Geomagnetic Polarity ◽

Geomagnetic Polarity Time Scale ◽

High Median

Twelve sites (57 drill cores) from two lava series and one dike were sampled for a palaeomagnetic study of the late Paleocene and early Eocene West Greenland flood basalts. Most of the rocks exhibited well-defined one component remanent magnetization with high unblocking temperatures (mostly above 500°C) and high median destructive fields (30–40 mT). All the rocks are reversely magnetized and, when combined with 40Ar/39Ar ages (Storey et al. 1998), a direct correlation with the geomagnetic polarity time scale can be made. Rock magnetic experiments indicate varying degree of both high temperature (deuteric) and low temperature (hydrothermal) oxidation of primary titanomagnetite. Twenty-three samples with high Curie point (~570°C) were chosen for Thellier palaeointensity experiments. Eleven of them, coming from three different cooling units, yielded reliable palaeointensity estimates. The results are reasonably coherent within sites, and the site-mean virtual dipole moments (VDM) are 1.8, 9.0 and 15.4×1022Am2 . The lowest VDM most probably corresponds to the ~94 ka long C24n.1r subchron, while the two other VDM’s close to present-day and higher than present-day values correspond to chrons C26r and C24r respectively.

Download Full-text

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

Vietnam Journal of Earth Sciences ◽

10.15625/2615-9783/15943 ◽

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.

Download Full-text

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

Vietnam Journal of Earth Sciences ◽

10.15625/0866-7187/15943 ◽

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

Download Full-text

40Ar/39Ar geochronology and paleomagnetism of Independence volcano, Absaroka Volcanic Supergroup, Beartooth Mountains, Montana

Canadian Journal of Earth Sciences ◽

10.1139/e96-125 ◽

1996 ◽

Vol 33 (12) ◽

pp. 1648-1654 ◽

Cited By ~ 13

Author(s):

Stephen S. Harlan ◽

Lawrence W. Snee ◽

John W. Geissman

Keyword(s):

Late Cretaceous ◽

Middle Eocene ◽

Paleomagnetic Data ◽

Volcanic Complex ◽

Reverse Polarity ◽

Virtual Geomagnetic Pole ◽

The Core ◽

Volcanic Breccia ◽

Geomagnetic Pole ◽

Volcanic Pile

Independence volcano is a major volcanic complex in the lower part of the Absaroka Volcanic Supergroup (AVS) of Montana and Wyoming. Recently reported Rb–Sr mineral dates from the complex give apparent ages of 91 and 84 Ma, whereas field relationships and the physical and compositional similarity of the rocks with other dated parts of the AVS indicate an Early to Middle Eocene age for eruption and deposition. To resolve the conflict between age assignments based on stratigraphic correlations and Rb–Sr dates, we report new paleomagnetic data and 40Ar/39Ar dates for Independence volcano. Paleomagnetic data for the stock and an andesite plug that cuts the stock are well grouped, of reverse polarity, and yield a virtual geomagnetic pole that is essentially identical to Late Cretaceous and Tertiary reference poles. The reverse polarity indicates that the magnetization of these rocks is probably younger than the Cretaceous normal superchron, or less than about 83.5 Ma. Hornblende from a volcanic breccia near the base of the volcanic pile gives a 40Ar/39Ar age of 51.57 Ma, whereas biotites from a dacite sill and a granodiorite stock that forms the core of the volcano give dates that range from 49.96 to 48.50 Ma. These dates record the age of eruption and intrusion of these rocks and clearly show that the age of Independence volcano is Early to Middle Eocene, consistent with stratigraphic relations. We suggest that the Rb–Sr mineral dates from the Independence stock and related intrusions are unreliable.

Download Full-text

Retrospective on the plate tectonic revolution focusing on K/Ar dating, linear volcanic chains and the geomagnetic polarity time scale

Earth Sciences History ◽

10.17704/eshi.32.2.p775346702221163 ◽

2013 ◽

Vol 32 (2) ◽

pp. 313-331 ◽

Cited By ~ 4

Author(s):

Ian McDougall

Keyword(s):

Time Scale ◽

Plate Tectonics ◽

Magnetic Measurements ◽

Volcanic Rocks ◽

Strong Support ◽

Ocean Ridges ◽

Quantitative Measurements ◽

Atmospheric Argon ◽

Geomagnetic Polarity ◽

Geomagnetic Polarity Time Scale

Notions of migration of volcanism in the Hawaiian Islands were contemplated for decades, but no quantitative measurements were made until the early 1960s. Collections of volcanic rocks from the accessible high islands were undertaken by the author in 1961. Surprisingly, K/Ar dating was possible, owing to much lower atmospheric argon in the samples than anticipated, allowing radiogenic argon to be detected. It became evident that there had been a progression of volcanism from Kauai (~4.4 Ma) in the WNW of the archipelago to the Island of Hawaii in the ESE, where there is active volcanism, with a rate of migration of volcanism averaging ~13-16 cm/year. These results gave strong support to J Tuzo Wilson's hotspot model for the origin of certain island chains, proposed in 1963. Later, rates determined in other Pacific island chains were concordant with Hawaii as indicators of direction and rate of plate motions. Concurrently with the successful Hawaiian age measurements, palaeomagnetic results were obtained by Don Tarling and combined with the K/Ar ages these showed that normal and reversed polarity zones were time related, and a geomagnetic polarity time scale was rapidly developed. Marine magnetic measurements across mid ocean ridges showed symmetry of parallel zones of magnetized crust, interpreted by Fred Vine and Drummond Matthews as reflecting normal and reversely magnetized new ocean floor, that was soon calibrated against the geomagnetic polarity time scale, providing persuasive evidence in favour of plate tectonics and seafloor spreading. But K/Ar dating was crucial to the major changes in tectonic hypotheses.

Download Full-text

Studi Awal Geologi di Daerah Beruang Kanan Kabupaten Gunung Mas Propinsi Kalimantan Tengah

PROMINE ◽

10.33019/promine.v6i1.710 ◽

2018 ◽

Vol 6 (1) ◽

pp. 1-11

Author(s):

Retno Anjarwati ◽

Arifudin Idrus ◽

Lucas Donny Setijadji

Keyword(s):

Gold Mineralization ◽

Volcanic Rocks ◽

Gold Deposits ◽

Central Kalimantan ◽

Magmatic Arc ◽

Tertiary Sediment ◽

Copper Gold ◽

Regional Tectonic ◽

Mineralization Processes ◽

High Yields

The regional tectonic conditions of the KSK Contract of Work are located in the mid-Tertiary magmatic arc (Carlile and Mitchell, 1994) which host a number of epithermal gold deposits (eg, Kelian, Indon, Muro) and significant prospects such as Muyup, Masupa Ria, Gunung Mas and Mirah. Copper-gold mineralization in the KSK Contract of Work is associated with a number of intrusions that have occupied the shallow-scale crust at the Mesozoic metamorphic intercellular junction to the south and continuously into the Lower Tertiary sediment toward the water. This intrusion is interpreted to be part of the Oligocene arc of Central Kalimantan (in Carlile and Mitchell 1994) Volcanic rocks and associated volcanoes are older than intrusions, possibly aged Cretaceous and exposed together with all three contacts (Carlile and Mitchell, 1994) some researchers contribute details about the geological and mineralogical background, and some papers for that are published for the Beruang Kanan region and beyond but no one can confirm the genesis type of the Beruang Kanan region The mineralization of the Beruang Kanan area is generally composed by high yields of epithermal sulphide mineralization. with Cu-Au mineralization This high epithermal sulphide deposition coats the upper part of the Cu-Au porphyry precipitate associated with mineralization processes that are generally controlled by the structure

Download Full-text

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

Earth Planets and Space ◽

10.1186/s40623-019-1107-6 ◽

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.

Download Full-text

On the interpretation of virtual geomagnetic pole (VGP) scatter curves

Physics of The Earth and Planetary Interiors ◽

10.1016/0031-9201(95)03106-5 ◽

1996 ◽

Vol 95 (1-2) ◽

pp. 37-53 ◽

Cited By ~ 40

Author(s):

Gauthier Hulot ◽

Yves Gallet

Keyword(s):

Virtual Geomagnetic Pole ◽

Geomagnetic Pole

Download Full-text

Geochronological and paleomagnetic studies of small carbonatite intrusions of the Udzha uplift (Tomtor massif, northeast of the Siberian platform)

10.5194/egusphere-egu21-12614 ◽

2021 ◽

Author(s):

Aleksandr Pasenko ◽

Ivanov Alexey ◽

Malyshev Sergey ◽

Travin Alexey

Keyword(s):

Siberian Platform ◽

Conclusive Evidence ◽

Snowball Earth ◽

Paleomagnetic Data ◽

Russian Science ◽

Virtual Geomagnetic Pole ◽

River Bank ◽

High Temperature Component ◽

Geomagnetic Pole ◽

Temperature Component

Paleomagnetic data obtained from Neoproterozoic glacial and glacier-associated sedimentary rocks indicate that they were formed at near equatorial latitudes. Based on these data, the Snowball Earth hypothesis was proposed [Kirschvink, 1992]. According to this hypothesis, during the Neoproterozoic glaciations, the entire planet (including the oceans) was completely covered with ice. Although evidence is emerging that does not support this hypothesis, there is still no conclusive evidence that it is not true [Sansjofre et al., 2011].It is worth noting that the Snowball earth hypothesis is based on paleomagnetic data. At the same time, the available paleomagnetic data for the Neoproterozoic-Early Cambrian [Meert, Van der Voo, 2001; Shatsillo et al, 2005; Abrajevitch, Van der Voo, 2010; Pavlov et al., 2018] difficult to interpret in terms of the Geocentric Axial Dipole hypothesis. This imposes serious restrictions on the possibility of correctly constructing paleomagnetic reconstructions.For the development and testing of a model of the geomagnetic field of the Neoproterozoic, it is necessary to obtain a lot of high-quality paleomagnetic data. Data from well-dated magmatic bodies are especially valuable.Within the framework of this work, we obtained paleomagnetic data from three carbonatite dikes (7 to 30 cm thickness) exposed in the Udzha river bank on the Udzha uplift in the northeastern part of the Siberian platform. These dikes are associated with the large alkaline Tomtor massif located 15 km to the west. Ar/Ar dating of phlogopite megacrysts gives an intrusion age of the dikes of 706.1&#177;8.8 Ma. Coordinates of the virtual geomagnetic pole, calculated from the direction of the high-temperature component of magnetization: &#934;=-20.7&#176;; &#923;=88.6&#176;; &#913;95=3.4&#176;.Our report will present preliminary interpretation of these data, as well as their comparison with paleomagnetic data on close-aged objects in Siberia.The research was supported by the Russian Science Foundation grant (19-77-10048).References:

Download Full-text