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.

该提案涉及亚得里亚（被亚得里亚海周围山脉带包围的大陆岩石圈）在阿尔卑斯-地中海构造演化中的作用，这是30多年来争论的主题。“阿德里亚问题”涉及的想法，阿德里安微板已表现为一个海角的非洲板块。这一观点得到了以前从亚德里亚获得的古地磁数据的支持，尽管这个问题由于亚德里亚沉积盖层的逆冲岩席旋转以及缺乏足够的非洲和亚德里亚古地磁数据而变得复杂。在侏罗纪和白垩纪亚德里亚的表观极移路径（APWP）中的一个“尖点”或“发夹”（Besse和Courtillot，1996）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没有足够好的定义，以建立一致性或文件偏移，这将意味着阿德里亚和Africa.To解决这些问题，这项研究是提供古磁极的关键晚侏罗世-早白垩世间隔从阿德里亚和非洲之间的相对旋转。在阿德里亚（意大利）的采样点将使晚侏罗世-早白垩世APWP的形状得以解决。将这些APWP与加尔加诺的APWP（据信不受逆冲岩片旋转的影响）进行比较，可以确定阿德里亚其他地方的逆冲岩片旋转量。我们的研究为非洲西北部提供了一个早白垩世的APWP，它可以精确地与极性地层相联系，从而与地质时间尺度相联系。这些数据将补充这一时间间隔内非常稀少的非洲数据，并提供一种与来自阿德里亚的数据以及Besse和Courtillot（2002年）的“合成”非洲APWP进行比较的手段。夹层玄武岩和透明碎屑岩在Maio的远洋部分的基础上提供了一种手段，连接极性地层绝对氩-氩同位素年龄急需的时标calibration.Our的研究将建立是否稳定的本土核心的Adria自中生代早期相对于非洲旋转。这个问题对阿尔卑斯山的构造至关重要，因此对了解阿尔卑斯山带的演变至关重要。该项目被整合到佛罗里达大学的学习体验中，学生将参与实地实验室数据采集和结果分析。