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dc.contributor.author Salminen J.M.
dc.contributor.author Donadini F.
dc.contributor.author Pesonen L.J.
dc.contributor.author Masaitis V.L.
dc.contributor.author Naumov M.V.
dc.date.accessioned 2024-12-22T03:48:01Z
dc.date.available 2024-12-22T03:48:01Z
dc.date.issued 2006
dc.identifier https://www.elibrary.ru/item.asp?id=13526174
dc.identifier.citation Meteoritics and Planetary Science, 2006, 41, 12, 1853-1870
dc.identifier.issn 1086-9379
dc.identifier.uri https://repository.geologyscience.ru/handle/123456789/47088
dc.description.abstract Paleomagnetic, rock magnetic, and petrophysical results are presented for impactites and target rocks from the Lake Jänisjärvi impact structure, Russian Karelia. The impactites (tagamites, suevites, and lithic breccias) are characterized by increased porosity and magnetization, which is in agreement with observations performed at other impact structures. Thermomagnetic, hysteresis, and scanning electron microscope (SEM) analysis document the presence of primary multidomain titanomagnetite with additional secondary titanomaghemite and ilmenohematite. The characteristic impact-related remanent magnetization (ChRM) direction (D = 101.5°, I = 73.10°, α95 = 6.2°) yields a pole (Lat. = 45.0°N, Long. = 76.9°E, dp = 9.9°, dm = 11.0°). Additionally, the same component is observed as an overprint on some rocks located in the vicinity of the structure, which provides proofs of its primary origin. An attempt was made to determine the anci ent geomagnetic field intensity. Seven reliable results were obtained, yielding an ancient intensity of 68.7 ± 7.6 μT (corresponding to VDM of 10.3 + 1.1 × 1022 Am2). The intensity, however, appears to be biased toward high values mainly because of the concave shape of the Arai diagrams. The ne w paleomagnetic data and published isotopic ages for the structure are in disagreement. According to well-defined paleomagnetic data, two possible ages for magnetization of Jänisjärvi rocks exist: 1) Late Sveconorwegian age (900-850 Myr) or 2) Late Cambrian age (~500 Myr). However, published isotopic ages are 718 ± 5 Myr (K-Ar) and 698 ± 22 Myr (39Ar-40Ar), but such isotopic dating methods are often ambiguous for the impactites. © The Meteoritical Society, 2006.
dc.subject Cambrian
dc.title PALEOMAGNETISM AND PETROPHYSICS OF THE JäNISJäRVI IMPACT STRUCTURE, RUSSIAN KARELIA
dc.type Статья
dc.identifier.doi 10.1111/j.1945-5100.2006.tb00456.x
dc.subject.age Paleozoic::Cambrian
dc.subject.age Палеозой::Кембрийская


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