Remanent magnetization of oolitic ironstone beds, Hazara area, Lesser Himalayan thrust zone, Northern Pakistan: Its acquisition, timing, and paleoenvironmental implications
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- Yoshida Mitsuo
- Geoscience Laboratory, Geological Survey of Pakistan
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- Khan Ibrar H.
- Geoscience Laboratory, Geological Survey of Pakistan
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- Ahmad Mirza Naseer
- Geoscience Laboratory, Geological Survey of Pakistan
書誌事項
- タイトル別名
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- Remanent magnetization of oolitic irons
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Chamosite-hematite type oolitic ironstone is distributed in the Cretaceous-Tertiary (K-T) boundary zone of the Hazara area, Lesser Himalayan thrust zone, in the northwestern margin of the Indo-Pakistani subcontinent. A total of 52 oriented samples were collected from 6 beds in two open pit mines, Nathia Gali and Bagnotar. Ferromagnetic properties of the oolitic ironstone are dominated by fine-grained hematite that possesses a characteristic remanent magnetization (ChRM). The ChRM is a chemical remanent magnetization (CRM) acquired by the hematite which formed from Fe-rich initial materials (iron hydroxides) during early diagenesis of the ironstone bed. The direction of the remanent magnetization indicates that the magnetization was acquired in an equatorial region (average inclination = 2°, paleolatitude = 1°N), which is consistent with the paleoposition of the Indian subcontinent during early Paleocene time, as estimated by previous data. The initial Fe-rich sediments were deposited under anoxic conditions, probably in a non-marine or brackish environment. During early diagenesis, after development of oolitic textures, the paleoenvironment became arid, where the CRM was acquired through the conversion of amorphous hydroxides or goethite to fine-grained hematite. The paleomagnetic results reveal complicated local rotational movements of oolitic ironstone blocks about vertical axes, which might be a result of intense thrusting within the terrane after early Tertiary collision between India and Asia.
収録刊行物
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- Earth, Planets and Space
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Earth, Planets and Space 50 (9), 733-744, 1998
地球電磁気・地球惑星圏学会 、公益社団法人 日本地震学会、特定非営利活動法人 日本火山学会、日本測地学会、日本惑星科学会
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詳細情報 詳細情報について
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- CRID
- 1390001206510270720
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- NII論文ID
- 10003735931
- 130003955930
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- NII書誌ID
- AA11211921
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- COI
- 1:CAS:528:DyaK1MXlsVeksw%3D%3D
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- ISSN
- 18805981
- 13438832
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- NDL書誌ID
- 4590643
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- 本文言語コード
- en
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- データソース種別
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- JaLC
- NDL
- Crossref
- CiNii Articles
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- 使用不可