Diese Seite ist aus Gründen der Barrierefreiheit optimiert für aktuelle Browser. Sollten Sie einen älteren Browser verwenden, kann es zu Einschränkungen der Darstellung und Benutzbarkeit der Website kommen!
Geophysics Homepage
Search:
Log in
print

Two normal paleomagnetic polarity intervals in the lower Matuyama Chron recorded in the Shungura Formation (Omo Valley, Southwest Ethiopia)

Kidane, Tesfaye, Yo-Ichiro Otofuji, Francis H. Brown, Kazuhiro Takemoto, and Getachew Eshete (2007), Two normal paleomagnetic polarity intervals in the lower Matuyama Chron recorded in the Shungura Formation (Omo Valley, Southwest Ethiopia), Earth and Planetary Science Letters, 262(1-2), 240 - 256, doi:10.1016/j.epsl.2007.07.047.

Abstract
Two hundred fifty meters of fluvio-lacustrine deposits were sampled from the 760-meter thick Shungura Formation to study magnetostratigraphy within the lower Matuyama Chron. Two to three block samples (at different positions) were collected from 46 units in the section. Characteristic remanent magnetization (ChRM) is isolated at temperatures between 390 °C and 620 °C or alternating fields between 25 and 100 mT. The ChRM is carried by detrital magnetite and maghemite. Directional analyses revealed three reversed and three normal polarity zones: R3–N3–R2–N2–R1–N1 in the sequence. The overall mean direction Ds = 359.1°, Is = 3.4°; ?95 = 3.9°, N = 44 differs marginally from the expected mean dipole field direction (D = 1.0°, I = 8.8°, ?95 = 2.3°, N = 26) [Besse, J., Courtillot, V., 2003. Apparent and True Polar wander and the geometry of the geomagnetic field in the last 200 million years. J. Geophys. Res. 108 (B10), 2469. doi 10.1029/2003JB002684]. Using stratigraphic scaling between 40Ar/39Ar and K/Ar isotopic age data [Brown, F.H., McDougall, I., Davies, I., Maier, R., 1985. An integrated Plio-Pleistocene chronology for the Turkana basin. In: Delson, E. (Ed.), Ancestors: The Hard Evidence. Alan R. Liss, Inc., New York, pp. 82–90; McDougall, I., Brown, F.H., 2006. Precise 40Ar/39Ar geochronology for the upper Koobi Fora Foramtions, Turkana Basin, northern Kenya. J. Geo. Soc. (Lond.) 163, 205–220], the normal zones N3, N2, and N1 are dated between 2.06 ± 0.01–2.08 ± 0.01 Ma, 2.15 ± 0.01–2.20 ± 0.01 Ma, and at 1.93 ± 0.02 Ma respectively. These age estimates imply that N1 represents the bottom of the Olduvai Subchron while N2 and N3 might represent Réunion Subchrons. If the sedimentation rates are assumed to be constant, the duration for the older Réunion (I) Subchron is about four to seven times (57 ± 15 kyr) that currently adopted by the recent GPTS [Cande, S.C., Kent, D.V., 1995. Revised calibration of the geomagnetic polarity timescale for the Late Cretaceous and Cenozoic. J. Geophys. Res. 100, 6093–6095] and the younger Réunion (II) Subchron has a shorter duration of 18 ± 25 kyr.
Further information
BibTeX
@article{id1575,
  author = {Tesfaye Kidane and Yo-Ichiro Otofuji and Francis H. Brown and Kazuhiro Takemoto and Getachew Eshete},
  journal = {Earth and Planetary Science Letters},
  number = {1-2},
  pages = {240 - 256},
  title = {{Two normal paleomagnetic polarity intervals in the lower Matuyama Chron recorded in the Shungura Formation (Omo Valley, Southwest Ethiopia)}},
  volume = {262},
  year = {2007},
  url = {http://www.sciencedirect.com/science/article/B6V61-4PB6W1C-6/2/ff3320609a873f956886bd546d0755c3},
  doi = {10.1016/j.epsl.2007.07.047},
}
EndNote
%0 Journal Article
%A Kidane, Tesfaye
%A Otofuji, Yo-Ichiro
%A Brown, Francis H.
%A Takemoto, Kazuhiro
%A Eshete, Getachew
%D 2007
%N 1-2
%V 262
%J Earth and Planetary Science Letters
%P 240 - 256
%T Two normal paleomagnetic polarity intervals in the lower Matuyama Chron recorded in the Shungura Formation (Omo Valley, Southwest Ethiopia)
%U http://www.sciencedirect.com/science/article/B6V61-4PB6W1C-6/2/ff3320609a873f956886bd546d0755c3
ImprintPrivacy PolicyContact
Printed 30. Oct 2020 20:50