Early Cretaceous Basalts of the Franz Josef Land Archipelago: Correspondence of New 40 Ar/ 39 Ar and Paleomagnetic Data
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Early Cretaceous Basalts of the Franz Josef Land Archipelago: Correspondence of New 40Ar/39Ar and Paleomagnetic Data V. V. Abasheva,b,*, D. V. Metelkina,b, Academician V. A. Vernikovskya,b, E. A. Vasyukovab,c, and N. E. Mikhaltsova,b Received April 14, 2020; revised April 14, 2020; accepted April 14, 2020
Abstract—The paper presents new 40Ar/39Ar age determination of basalts from the Franz Josef Land archipelago. The obtained set of dates confirms the predominance of products only of Early Cretaceous age, which is also confirmed by results of paleomagnetic studies. Analysis of the entire set of geochronological data, taking into account information on their magnetic polarity, indicates that the interval of active magmatism occurred at the latest Barremian–Aptian and corresponds to the beginning of the Cretaceous Normal Superchron (C34n) at about 125 Ma. Significantly older age estimates are not related to the time of formation of the FJL basalts as a part of the High Arctic Large Igneous Province. Keywords: geochronology, paleomagnetism, large igneous provinces, Franz Josef Land archipelago, Arctic DOI: 10.1134/S1028334X2007003X
The emplacement of the High Arctic Large Igneous Province (HALIP) is a fundamentally important stage in the tectonic evolution of the high-latitude Arctic region. Its fragments were preserved as volcanic plateaus, submerged rises and islands adjacent to the Eurasian and Amerasian basins of the Arctic Ocean [1]. In this context, the islands of the Franz Josef Land archipelago (FJL) are a key site for reconstructing the Barents Sea part of HALIP. Systematic studies of the archipelago have been ongoing for a long time [2], however, views on the age and duration of the magmatic event that led to its formation are contradictory to this day. Recently obtained 40Ar/39Ar ages indicate a wide range in the time of magmatism on FJL – from the Early Jurassic to the Early Cretaceous, including three pulses at 190 Ma, 155 Ma, and 125 Ma [3, 4]. Other geochronological data, including singular U–Pb determinations, limit the formation of the FJL traps to one brief pulse in the Early Cretaceous [5, 6]. This is corroborated by abundant paleontological data, results of geological mapping and interpretation of regional geophysical fields, and other geological and geophysical observations, confirming that the flood a Trofimuk
Institute of Petroleum Geology and Geophysics, SB RAS, Novosibirsk, 630090 Russia b Novosibirsk State University, Novosibirsk, 630090 Russia c Sobolev Institute of Geology and Mineralogy, SB RAS, Novosibirsk, 630090 Russia *е-mail: [email protected]
basalts are underlain by sedimentary rocks not older than the Oxfordian [7–9]. Our new paleomagnetic data also indicate that the formation of the FJL magmatic region was brief and constituted a single event [10, 11]. Obtained paleomagnetic vectors and corresponding virtual geomagnetic poles do not form any discrete groups that would be expected in the case of episodic magmatism with prolonged episodes of relative calm [10]. Studying
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