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Please use this identifier to cite or link to this item: http://hdl.handle.net/123456789/2523

Title: PALEOMAGNETISM AND TECTONICS OF MANDA HARARO RIFT OF NORTH AFAR, ETHIOPIA
Authors: AMEHA, ATNAFU
Advisors: Dr. Tesfaye Kidane
Copyright: Jan-2010
Date Added: 4-May-2012
Abstract: Abstract This study explains tectonics and Paleomagnetism of Manda Hararo rift in north afar. The field trip which was organized by scientists from New Zealand, Ethiopia and UK was made to study the Dabbahu magmatic segment in northern part of Manda Hararo rift. A total of 271 oriented core samples were collected for paleomagnetic study from 34 sites within Manda Hararo rift. Available age data of Basalts from the sampled localities show that the age ranges between 0.09Ma to 1.11Ma. 175 specimens were subjected to progressive Alternating Field (AF) demagnetization after routine sample preparation in the laboratory. Almost all specimens show fairly simple demagnetization behavior. AF between 0 to 30mT often isolates the first component. Median Destructive Field for most specimens ranges between 20 and 35mT, suggesting that Pseudo single domain grains as remnant magnetization carriers. Among 34 sites, 30 sites show normal polarities and four sites show reversed polarities. The normal and reversed polarities are 1800 apart, showing that the ChRM are free of secondary NRM components. Magnetic polarities were found to be coincident with Geomagnetic Polarity Time Scale (GPTS) of Cande and Kent (1995). Geomagnetic Polarity Time Scale of Langeries et al., (1997), Lund et al., (1998) and Nowaczyk & Frederichs (1999) were used to explain and determine age of the reversed polarity site PMAF04 from Afdera. The overall mean direction for 33 sites is D=357.10, I=10.60 (k=32.6 and α95=4.40). Comparison of observed mean direction with predicted direction of Kidane et al., 2003 for stable Africa for ~2Ma (D=359.70, I=16.40, α95=5.70), indicates no statistically significant vertical axis rotation has occurred in Manda Hararo rift. Comparison of mean direction from Kori and Saha with the predicted direction of Kidane et al., 2003 indicates that significant amount of counter clock wise rotation (~5.90±8.60) has occurred. Further comparison of mean values from the two sites with the Apparent Polar Wander Path curve of Besse and Courtillot, 1991, shows a counter clock wise rotation of 7.10±6.70. This local rotation is due to the overlap of Red Sea propagators, Erta’ale-Dader in the east and Erta’ale-Manda Hararo in the west. A reference pole is determined based on 33 sites. It is located at λ=83.10N, ф=238.80E(α95=4.00).
URI: http://hdl.handle.net/123456789/2523
Appears in:Thesis - Earth Sciences

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