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SINET: Ethiopian Journal of Science

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Paleomagnetic dating of the Enticho sandstone at negash locality (Tigrai Region, northern Ethiopia): implication for quaternary remagnetization

Tesfaye Kidane

Abstract


New paleomagnetic result is reported from the Enticho Sandstone (Late Paleozoic age) at Negash locality in Northern Ethiopia. Twenty-three paleomagnetic core samples were collected from three sites for paleomagnetic investigations. Specimens were subjected either to progressive alternating field (af) or thermal (th) demagnetization techniques. Rock magnetic experiments revealed major magnetization carriers to be titano-magnetite and titano-hematite. Well-defined viscous remanent magnetizations (vrm) components are removed by intermediate af fields of between 20–30 mT and heating above 600ºC. These magnetizations defining straight-line segments are directed towards the origin and interpreted as the Characteristic Remanent Magnetization (ChRM). Directions of magnetizations and site-mean directions in the in-situ coordinate results in Dec = 356.7°, Inc = 24.9º (N=23, K = 43, a95 = 4.7°). Paleomagnetic stability tests confirmed that the ChRMs identified are secondary and postdate age of deposition and tectonic tilting. The paleomagnetic pole position Long = 296.6ºE, Lat = 86.7ºN (A95 = 5.0º, N = 23) obtained from these data when plotted with the Apparent Polar Wander Path (apwp) of Africa (Besse and Courtillot, 1991, 2003; Cogné, 2003) gives a Quaternary age for the magnetization of Enticho Sandstone at Negash locality. Comparison of this result with that of Enticho Sandstone at Enticho locality, which had primary magnetization fingerprints (Tesfaye Kidane et al., 2013) with ages of between 260 Ma and 270 Ma (Late Carboniferous – Early Permian) implies that the Quaternary age for the Enticho Sandstone at Negash is a recent remagnetization.



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