The Red Bed Paleomagnetic Inclination Correction and the Accuracy of the Late Paleozoic North American Apparent Polar Wander Path

红层古地磁倾角修正与北美晚古生代视极地漂移路径的准确性

• 批准号: 0207275
• 负责人: Kenneth Kodama
• 金额: $ 17.84万
• 依托单位: Lehigh University
• 依托单位国家: 美国
• 项目类别: Continuing Grant
• 财政年份: 2002
• 资助国家: 美国
• 起止时间: 2002-06-01 至 2007-05-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=0207275&HistoricalAwards=false
• 关键词: Red; Bed; Paleomagnetic; Inclination; Correction

The proposed work will investigate how the PI's recent magnetic anisotropy studies, showing that hematite-bearing red sedimentary rocks can suffer up to 30 degrees of inclination shallowing, impact the accuracy of the Late Paleozoic North American apparent polar wander path. Red bed paleopoles dominate and control the position of the Late Paleozoic to mid-Mesozoic portion of North America's apparent polar wander path, thus inaccuracies in red bed remanence would greatly affect any paleogeographies based on this part of the pole path. the PI's previous NSF-funded study has shown that a combination of isothermal remanence anisotropy and anisotropy of magnetic susceptibility can be used to identify and correct inclination shallowing in red, hematite-bearing sedimentary rocks. By using thermal demagnetization and chemical demagnetization, the magnetic fabric of the characteristic remanence-carrying grains can be isolated. This is critical for an accurate inclination correction. Though initial tests of the accuracy of these corrections support their validity, given the importance of red beds to the Late Paleozoic North American apparent polar wander path, the PI proposes to further test the accuracy of the corrected inclination he has determined for the Carboniferous Mauch Chunk Formation. Igneous paleopoles would be the best way to test the corrected inclination, but igneous results for Carboniferous North America are few and scattered. Therefore, his strategy is to collect and correct the inclinations of other red bed units, and magnetite-bearing sedimentary rocks, of the same age as the Mauch Chunk. If magnetic anisotropy does truly control the accuracy of remanence, the corrected paleopoles should agree with each other. The corrected magnetite-bearing inclinations from the Brush Creek Limestone and Buffalo Siltstone in Pennsylvania will be particularly important since the PI has established the accuracy of the magnetite correction from a comparison of corrected results from the Paleocene Nacimiento Formation to coeval igneous results. He will correct the inclinations of the Maringouin, Shepody, and Enrage Formation red beds from New Brunswick, Canada and the Deer Lake Group rocks from western Newfoundland for the red bed part of the comparison. These rocks have given excellent Carboniferous age paleomagnetic results for North America. Finally, although Carboniferous North American igneous results are scattered, the PI plans to restudy the remanence of the New Brunswick Volcanics, given their proximity to the other New Brunswick units he proposes to study. He wishes to check the accuracy and age of the New Brunswick Volcanics remanence to make sure they provide a reliable record of the Carboniferous field. The proposed work will be conducted over three years, including three field seasons, and will support a graduate student's PhD dissertation work at Lehigh University.

这项工作将调查PI最近的磁各向异性研究如何影响晚古生代北美视极移路径的准确性。研究表明，含赤铁矿的红色沉积岩可能会遭受高达30度的倾斜变浅。红层古磁极主导并控制了晚古生代至中生代中期北美视极移路径的位置，因此，红层剩磁的不准确性将极大地影响任何基于这部分极径的古地理学。PI先前由NSF资助的研究表明，等温剩磁各向异性和磁化率各向异性的组合可用于识别和校正红色含赤铁矿沉积岩中的倾斜变浅。通过热退磁和化学退磁，可以分离出特征剩磁颗粒的磁组构。这对于精确的倾斜校正至关重要。虽然这些校正的准确性的初步测试支持其有效性，考虑到红层对晚古生代北美表观极移路径的重要性，PI建议进一步测试他为石炭纪Mauch Chunk地层确定的校正倾斜的准确性。火成岩古磁极是检验校正倾斜的最好方法，但北美石炭纪火成岩结果很少且分散。因此，他的策略是收集和校正其他红层单位的倾斜度，以及与Mauch Chunk同龄的含磁铁矿沉积岩。如果磁各向异性确实控制了剩磁的准确性，则校正后的古极点应该彼此一致。宾夕法尼亚州的Brush Creek石灰岩和布法罗粉砂岩的磁铁矿含矿倾斜度的校正将特别重要，因为PI已通过古新世纳西米恩托地层的校正结果与同时代火成岩结果的比较确定了磁铁矿校正的准确性。他将校正来自加拿大新玩法的马林古安、谢波迪和愤怒组红层以及来自纽芬兰西部的鹿湖群岩石的倾斜度，以进行红层比较。这些岩石为北美石炭纪的古地磁研究提供了极好的结果。最后，尽管石炭纪北美火成岩的结果是分散的，PI计划重新研究新玩法火山的剩磁，因为他们接近其他新玩法单位，他建议研究。他希望检查新玩法火山残留的准确性和年龄，以确保它们提供石炭纪油田的可靠记录。拟议的工作将在三年内进行，包括三个领域的季节，并将支持研究生的博士论文工作在利哈伊大学。