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首页> 外文期刊>NRIAG Journal of Astronomy and Geophysics >Magnetization of three Nubia Sandstone formations from Central Western Desert of Egypt
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Magnetization of three Nubia Sandstone formations from Central Western Desert of Egypt

机译：来自埃及中西部沙漠的三个努比亚砂岩地层的磁化

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A total of 198 oriented cores (from 16 sites) have been sampled from three Cretaceous Nubia sandstone formations distributed around the Kharga–Dakhla and Dakhla–Uwainat roads in the Western Desert for paleomagnetic studies. Two of these formations are of the Early Cretaceous (the Six Hills, Abu Ballas formations) and the third one is of the Late Cretaceous (Maghrabi formation). The studied rocks are subjected to rock magnetic measurements as well as demagnetization treatment.Rock magnetic experiments reveal that the presence of hematite is the main magnetic mineral in the three formations. Therefore, present study relies mostly on thermal demagnetization.Two magnetic components have been isolated from the studied rocks. The first component has been isolated from the Six Hills and Abu Ballas formations and is carried by hematite withD=347.1°,I=41.6° withα95=7.8° and the corresponding pole lies at lat.=78.2° N and long.=294.1° E. The second component has been isolated from the Maghrabi formation and is carried also by hematite withD=22.7°,I=28.4° withα95=9.9° and pole position lies at lat.=66.3° N and long.=140.6° E.The first magnetic component obtained from the two older formations is considered primary, as the corresponding pole reflects the age when compared with the previously obtained Cretaceous poles for North Africa. On other hand, the second pole obtained from the Maghrabi formation (the younger) is inconsistent with the Cretaceous pole positions for North Africa, but falls closer to the Eocene pole indicating that the rocks of this formation could have suffered remagnetization during the late Eocene time.
机译：从分布在西部沙漠Kharga-Dakhla和Dakhla-Uwainat公路周围的三个白垩纪努比亚砂岩地层中，总共采样了198个定向岩心（来自16个站点），用于古地磁研究。这些地层中的两个是白垩纪早期（六山，阿布巴拉斯地层），第三个是白垩纪晚期（马格拉比地层）。所研究的岩石经受了岩石磁测量以及去磁处理。岩石磁实验表明，赤铁矿的存在是这三个地层中的主要磁性矿物。因此，目前的研究主要依靠热退磁。从研究的岩石中分离出两个磁性成分。第一部分已从六山丘和阿布巴拉斯地层中分离出来，由赤铁矿携带，D = 347.1°，I = 41.6°，α95= 7.8°，相应的极点位于纬度= 78.2°N，长= 294.1° E.第二个成分已从马格拉比地层中分离出来，也由赤铁矿携带，D = 22.7°，I = 28.4°，α95= 9.9°，极点位置位于纬度= 66.3°N，长= 140.6°E。从这两个较早的地层中获得的第一磁性成分被认为是主要的，因为与先前获得的北非白垩纪磁极相比，相应的磁极反映了年龄。另一方面，从马格拉比组（较年轻）获得的第二极与北非的白垩纪极位置不一致，但下降到始新世极附近，这表明该地层的岩石可能在始新世末期遭受了磁化作用。 。

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