A new Late Cretaceous paleomagnetic pole for the west of Amuria block (Khunnen Uul, Mongolia) | INSTITUT DE PHYSIQUE DU GLOBE DE PARIS

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  A new Late Cretaceous paleomagnetic pole for the west of Amuria block (Khunnen Uul, Mongolia)

Type de publication:

Journal Article

Source:

Earth and Planetary Science Letters, Volume 236, Ticket 1-2, p.359-373 (2005)

ISBN:

0012-821X

URL:

http://www.sciencedirect.com

Mots-clés:

TIEN-SHAN

Résumé:

We present new paleomagnetic results obtained at ten sampling sites from six Upper Cretaceous (92 +/- 4 Ma) basaltic lava flows from the westernmost part of Amuria block. The samples were collected in 1999 in the Khurmen Uul region (44.0 degrees N, 103.0 degrees E), Gobi desert (S. Mongolia). Stepwise thermal demagnetization isolated a high temperature component (HTC) carried by magnetite. Five out of ten sites exhibit anomalously high Koenigsberger ratios and low inclinations, which likely resulted from lightning remagnetization. However, three of these sites were only partially remagnetized, allowing us to use remagnetization great-circles to help determine a characteristic magnetization direction for this formation. HTC directions of the eight remaining sites from six distinct flows all possess normal polarity and exhibit better clustering after tilt correction of the flows (ks/kg = 129.3/36.6, n = 6). This clustering is ascertained by a positive fold test at the specimen scale within a single flow. We therefore propose that the tilt-corrected HTC represents a primary magnetization. The paleopole computed from the six lava flows HTC mean directions lies at lambda =71.5 degrees N, phi =227.2 degrees E (dp/dm = 5.6 degrees/8.2 degrees). We discuss the possibility that our pole might not have completely averaged paleosecular variation, because it is based on only 6 independent flows. Finally, this pole is far-sided with respect to the 90 Ma reference pole of Eurasia APWP (Delta lambda = 10.2 degrees +/- 6.1 degrees), but it is consistent, albeit somewhat far-sided too, with other coeval paleopoles from Amuria, and east China. (c) 2005 Elsevier B.V. All rights reserved.

Notes:

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