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Abstract
Abstract Samples were obtained from three baked contacts and one lava flow along the upper Turonian-lower Coniacian Tovuz section, two baked contacts along the upper Coniacian-lower Santonian Paravakar section in the northern part of Armenia, and three baked contacts along the Titonian-Valanginian Kafan section in southern Armenia. A total of 130 samples were studied. Updated mean paleomagnetic poles were calculated for the Upper Cretaceous Tovuz-Paravakar sections (65.6°N, 162.2°E, A95 = 4.3, paleolatitude = 27.0 ± 3.4°) and the Upper Jurassic-Lower Cretaceous Kafan section (61.7°N, 158.9°E, A95 = 4.8°, paleolatitude = 24.7 ± 3.8°). Paleointensity determinations could be estimated from two of the upper Cretaceous and three of the Upper Jurassic-Lower Cretaceous baked contacts, corresponding to a 30% success rate. The mean virtual dipole moments obtained were low (1.7-5.5 × 1022 A m2), which is in agreement with data published by Bol’shakov and Solodovnikov (1981a, 1983) for the same sections (3.0-4.4 × 1022 A m2). Our results support the hypothesis of the Mesozoic Dipole Low, even though the overall data are widely dispersed.
Highlights
Knowledge of the basic characteristics of the ancient geomagnetic field provides valuable information about the formation and evolution of the solid inner core, mantle, and outer shells of the Earth
We present the paleointensity results obtained on part of the Armenian collection, mainly baked contacts
The evidence for the primary origin of the characteristic remanent magnetization (ChRM) of these rocks is a good argument for considering these rocks for paleointensity experiments
Summary
Knowledge of the basic characteristics of the ancient geomagnetic field provides valuable information about the formation and evolution of the solid inner core, mantle, and outer shells of the Earth. The baked contacts from the Kafan section had a mean ChRM direction (Fig. 3(e, f)) that was statistically indistinguishable (γ /γc = 12.7◦/14.3◦; McFadden and McElhinny, 1990) from that obtained earlier by Bol’shakov and Solodovnikov (1983), after seven outliers with westerly declinations had been removed from the data set (see Fig. 3(e)). These directions, significantly different from all other normal and reverse directions, do not likely reflect the true direction of the ancient geomagnetic field and were interpreted by Bol’shakov and Solodovnikov (1983) as reflecting a transitional state of the geomagnetic field. Curie temperatures estimated from the Mrs(T ) and NRM(T ) thermodemagnetization curves agree well with those determined from the Ms(T ) curves, thereby confirming cation-deficient magnetite as the main carrier of the magnetic remanence
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