Mesozoic Paleomagnetism in Adria and Africa: Solving a Persistent Puzzle in Alpine Tectonics

亚德里亚和非洲的中生代古地磁：解决阿尔卑斯构造中的一个长期难题

• 批准号: 0337102
• 负责人: James Channell
• 金额: --
• 依托单位: University of Florida
• 依托单位国家: 美国
• 项目类别: Continuing Grant
• 财政年份: 2004
• 资助国家: 美国
• 起止时间: 2004-01-01 至 2008-12-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=0337102&HistoricalAwards=false
• 关键词: Mesozoic; Paleomagnetism; Adria; Africa; Solving

The proposal is addressing the role of Adria (the continental lithosphere encircled by the peri-Adriatic mountain belts) in the evolution of Alpine-Mediterranean tectonics, which has been a subject of debate for over 30 years. The "Adria problem" involves the idea that the Adrian microplate has behaved as a promontory of the African plate. This idea has since been supported by previously obtained paleomagnetic data from Adria, although the issue is complicated by the thrust sheet rotation of sedimentary cover on Adria and by the lack of adequate paleomagnetic data from Africa and Adria. A "cusp" or "hairpin" in the Jurassic and Cretaceous apparent polar wander path (APWP) for Adria (Channell, 1996) appears to fit with the recently published 'synthetic' African APWP (Besse and Courtillot, 2002). The two APWPs are, however, not sufficiently well defined to establish coherency or document offsets that would imply relative rotation between Adria and Africa.To resolve these issues, this study is providing paleomagnetic poles for the critical Late Jurassic-Early Creteceous interval from both Adria and Africa. Sampling sites on Adria (Italy) will allow the shape of the Late Jurassic-Early Cretaceous APWP to be resolved. Comparison of these APWPs with those from Gargano (believed to be unaffected by thrust sheet rotation) with allow the amount of thrust sheet rotation elsewhere on Adria to be ascertained. Our study is providing an Early Cretaceous APWP for NW Africa that can be precisely linked to a polarity stratigraphy and hence to the geologic timescale. These data will augment the very sparse African data for this time interval and provide a means of comparison with the data from Adria and with the 'synthetic' African APWP of Besse and Courtillot (2002). Intercalated basalts and hyaloclastites at the base of the pelagic section on Maio provide a means of linking the polarity stratigraphy to absolute argon-argon isotopic ages for much-needed timescale calibration.Our research will establish whether the stable autochthonous core of Adria has rotated relative to Africa since Early Mesozoic. The question is critical to Alpine tectonics, and hence to understanding the evolution of the Alpine belt. The project is integrated into the learning experience at the University of Florida, and students will participate in fieldwork laboratory acquisition of data, and analysis of results.

该提案旨在解决亚得里亚海（被亚得里亚海周边山脉环绕的大陆岩石圈）在阿尔卑斯-地中海构造演化中的作用，这一直是 30 多年来争论的话题。 “阿德里安问题”涉及阿德里安微板块充当非洲板块海角的想法。此后，这一想法得到了先前从阿德里亚获得的古地磁数据的支持，尽管由于阿德里亚沉积盖层的逆冲片旋转以及缺乏来自非洲和阿德里亚的足够古地磁数据，问题变得复杂。阿德里亚（Channell，1996）侏罗纪和白垩纪表观极地漂移路径（APWP）中的“尖点”或“发夹”似乎与最近发表的“合成”非洲 APWP（Besse 和 Courtillot，2002）相符。然而，这两个 APWP 的定义还不够明确，无法建立暗示亚德里亚和非洲之间相对旋转的一致性或记录偏移。为了解决这些问题，这项研究正在为亚德里亚和非洲关键的晚侏罗世 - 早白垩世区间提供古地磁极。阿德里亚（意大利）的采样点将有助于解析晚侏罗世-早白垩世 APWP 的形状。将这些 APWP 与来自加尔加诺的 APWP（据信不受推力片旋转影响）进行比较，可以确定阿德里亚其他地方的推力片旋转量。我们的研究为西北非洲提供了早白垩世 APWP，它可以精确地与极性地层学联系起来，从而与地质时间尺度联系起来。这些数据将补充该时间间隔内非常稀疏的非洲数据，并提供与阿德里亚的数据以及 Besse 和 Courtillot（2002）的“合成”非洲 APWP 进行比较的方法。马尤远洋部分底部的夹层玄武岩和玻璃碎屑岩提供了一种将极性地层学与绝对氩-氩同位素年龄联系起来的方法，以进行急需的时间尺度校准。我们的研究将确定阿德里亚稳定的本土核心自中生代早期以来是否相对于非洲发生了旋转。这个问题对于高山构造至关重要，因此对于理解高山带的演化也至关重要。该项目融入了佛罗里达大学的学习体验，学生将参与实地工作实验室采集数据，并对结果进行分析。