Oxidation processes and their effects on the magnetic remanence of Early Cretaceous subaerial basalts from Sierra Chica de Córdoba, Argentina

2014 ◽  
Vol 396 (1) ◽  
pp. 239-263 ◽  
Author(s):  
S. E. Geuna ◽  
S. L. Lagorio ◽  
H. Vizán
Keyword(s):  
Early Cretaceous ◽  
Oxidation Processes ◽  
Magnetic Remanence

The first definition of paleointensity in the Early Cretaceous basalts from the Franz Josef Land

2020 ◽  
Author(s):  
Evgeniy Vinogradov ◽  
Andrey Eliseev ◽  
Dmitriy Metelkin ◽  
Victor Abashev ◽  
Valery Vernikovsky ◽  
...  
Keyword(s):  
Magnetic Field ◽  
Early Cretaceous ◽  
Natural Remanent Magnetization ◽  
Sampling Point ◽  
Franz Josef Land ◽  
Magnetic Remanence ◽  
Definition Of ◽  
Day Plot ◽  
Ti Content ◽  
Paleomagnetic Direction

<p>We present the first definition of paleointesity of the Earth’s magnetic field that were obtained in the Early Cretaceous igneous rocks from the Franz Josef Land archipelago (Hooker and Scott Kelty Islands). The age of magmatism was determined by U-Pb method as the Early Cretaceous, about 125 Ma. A mean paleomagnetic direction for these rocks was calculated as D=40.2 deg, I=75.5 deg, a95=2.1 deg, k=89.3, N=52. A corresponding paleomagnetic pole is now located at Plat=69.0 deg; Plon=180.3 deg, A95=3.7 deg. An assessment of the domain structure of ferrimagnets using the Day plot diagram shows that the carriers of the natural remanent magnetization are pseudo-single-domain grains of titanomagnetites with varying Ti-content. Magnetic remanence was unblocked in temperatures of 350-400 °C. Some samples are characterized by unblocking temperatures of 560 °C. The determinations of the absolute values of paleointensity were obtained by the Thellier-Coe method with the implementation of the procedure "check-points". The values of B<sub>anc</sub> vary within 8.4–16 µT, which is noticeably lower than the current magnetic field at the sampling point ≈55 µT. The corresponding VDMs of 1.13–2.25 × 10<sup>22</sup> Am<sup>2</sup>, with the current value of VDM ≈8 × 10<sup>22</sup> Am<sup>2</sup>. Numerous basalt flows are well studied by paleomagnetic and rockmagnetic methods, together with a large number of geochronological definitions, this makes basalts from the Franz Josef Land promising for obtaining new qualitative determinations of paleointensity in the Early Cretaceous time.</p><p>This work was supported by the RSF (project no. 19-17-00091) and the RFBR (project nos. 18-35-00273, 18-05-70035).</p>

Early Cretaceous insect camouflage

AccessScience ◽  
2015 ◽  
Keyword(s):  
Early Cretaceous

Paleobiogeographic Distribution of the Early Cretaceous Radiolarian Turbocapsula costata and Its Correlation Potential

2020 ◽  
Vol 24 (2) ◽  
pp. 89
Author(s):  
Xin Li ◽  
Atsushi Matsuoka
Keyword(s):  
Early Cretaceous ◽  
Correlation Potential

PALEOGEOGRAPHY OF THE EARLY CRETACEOUS PYAKYAKHINO-KHALMERPAYUTINSKY SWELL BASIN ACCORDING TO LITHOGEOCHEMICAL RESEARCH DATA

2020 ◽  
pp. 80-86
Author(s):  
Yu.V. Titov ◽  
◽  
S.V. Astarkin ◽  
K.V. Pavlenko ◽  
G.M. Galimova ◽  
...  
Keyword(s):  
Early Cretaceous ◽  
Research Data

Ginkgophytes of the Ul’ya flora (the Ul’ya depresiion, the Okhotsk-Chukotka volcanogenic belt)

Palaeobotany ◽  
2016 ◽  
Vol 7 ◽  
pp. 80-95 ◽  
Author(s):  
L. B. Golovneva
Keyword(s):  
New Species ◽  
Early Cretaceous ◽  
Late Cretaceous ◽  
Middle Part ◽  
Leaf Length ◽  
Volcanogenic Belt ◽  
Short Shoots ◽  
Volcanogenic Deposits

The Ul’ya flora comes from the Coniacian volcanogenic deposits of the Amka Formation (the Ul'ya depression, southern part of the Okhotsk-Chukotka volcanogenic belt). Ginkgoaleans are diverse in this flora and represented by three genera: Ginkgo, Sphenobaiera and Baiera. All specimens have no cuticle and were assigned to morphotaxa. Genus Ginkgo includes two species: G. ex gr. adiantoides (Ung.) Heer with entire leaves and G. ex gr. sibirica Heer with dissected leaves. Genus Sphenobaiera also consists of two species: S. ex gr. longifolia (Pom.) Florin with 4–8 leaf lobes and S. ex gr. biloba Prynada with two leaf lobes. Genus Baiera is represented by new species B. lebedevii Golovn., sp. nov.Leaves of this species are 25–30 cm long and 13–16 cm wide, narrowly wedge-shaped with flat slender petiole, dichotomously dissected 4–5 times into linear segments 3–6 mm wide with 6–12 veins. The length of ultimate segments is equal to about a half of leaf length. Leaves attached spirally to ovoid short shoots about 2 cm long. Among the Late Cretaceous floras similar diversity of ginkgoaleans was recorded only in the Turonian-Coniacian Arman flora from middle part of the Okhotsk-Chukotka volcanogenic belt (Herman et al., 2016). Four species of ginkgoaleans from the Ul’ya flora (except G. ex gr. adiantoides) are considered as the Early Cretaceous relicts.

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