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An Integrated Paleomagnetic, Multimethod‐Paleointensity, and Radiometric Study on Cretaceous and Paleogene Lavas From the Lesser Caucasus: Geomagnetic and Tectonic Implications
Author(s) -
CalvoRathert M.,
Bógalo M. F.,
Morales J.,
Goguitchaichvili A.,
Lebedev V. A.,
Vashakidze G.,
GarcíaRedondo N.,
HerreroBervera E.
Publication year - 2021
Publication title -
journal of geophysical research: solid earth
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.983
H-Index - 232
eISSN - 2169-9356
pISSN - 2169-9313
DOI - 10.1029/2020jb020019
Subject(s) - paleomagnetism , paleogene , geology , earth's magnetic field , paleontology , cretaceous , apparent polar wander , geomagnetic pole , radiometric dating , polar wander , magnetic field , physics , quantum mechanics
Sixteen rhyolitic and dacitic Cretaceous and Paleocene‐Eocene lavas from the Lesser Caucasus have been subjected to paleomagnetic and multimethod paleointensity experiments to analyze the variations of the Earth's magnetic field. Paleointensity experiments were performed with two methods. Thellier‐type experiments with the IZZI method on 65 specimens (nine flows) yielded 15 successful determinations and experiments with the multispecimen method on 14 samples (seven flows) yielded two successful determinations. The joint analysis of the results obtained with both methods produced a mean F uK = (19.9 ± 3.7) µT for upper Cretaceous and F Pg = (20.7 ± 3.3) µT for Paleogene sites. Low virtual axial dipole moments for the Cretaceous (3.4 × 10 22 Am 2 ) and Paleogene (3.5 × 10 22 Am 2 ) samples support the idea of a lower average dipole moment during periods of stable polarity of the Earth magnetic field. Mean flow paleomagnetic directions did not match expected upper Cretaceous to Paleogene directions calculated from the European Apparent Polar Wander Path . While inclination results roughly agreed with expected values, a group of sites showed nearly North‐South paleodeclinations ( D = 1.1° ± 14.2°), and another group displayed eastward deviated paleodeclinations ( D = 72.9° ± 26.6°). These results suggest the occurrence of nearly vertical‐axis rotations, probably as a result of continental collision since Oligocene. In addition to paleomagnetic and palaeointensity analyses, new K‐Ar absolute age determinations have been performed on three of the studied sites, yielding Late Cretaceous ages (78.7 ± 1.7, 79.7 ± 1.6, and 83.4 ± 1.8 Ma (2 σ )).