Physics
Scientific paper
Oct 2007
adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2007e%26psl.262..240k&link_type=abstract
Earth and Planetary Science Letters, Volume 262, Issue 1-2, p. 240-256.
Physics
2
Scientific paper
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°; α95 = 3.9°, N = 44 differs marginally from the expected mean dipole field direction (D = 1.0°, I = 8.8°, α95 = 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.
Brown Francis H.
Eshete Getachew
Kidane Tesfaye
Otofuji Yo-Ichiro
Takemoto Kazuhiro
No associations
LandOfFree
Two normal paleomagnetic polarity intervals in the lower Matuyama Chron recorded in the Shungura Formation (Omo Valley, Southwest Ethiopia) does not yet have a rating. At this time, there are no reviews or comments for this scientific paper.
If you have personal experience with Two normal paleomagnetic polarity intervals in the lower Matuyama Chron recorded in the Shungura Formation (Omo Valley, Southwest Ethiopia), we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Two normal paleomagnetic polarity intervals in the lower Matuyama Chron recorded in the Shungura Formation (Omo Valley, Southwest Ethiopia) will most certainly appreciate the feedback.
Profile ID: LFWR-SCP-O-1068112