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.

该提议是针对阿德里亚（Adria）的作用（祭祀山地带包围的大陆岩石圈）在高山 - 中甲构造的演变中，这已经是辩论已有30多年了。 “阿德里亚问题”涉及这样的想法，即阿德里安·微板块表现为非洲板块的海角。此后，这一想法得到了以前从阿德里亚（Adria）获得的古磁数据的支持，尽管该问题是由于沉积物覆盖物在阿德里亚（Adria）上的推力旋转以及缺乏非洲和阿德里亚（Adria）的足够的古磁数据而变得复杂。侏罗纪和白垩纪明显的极地徘徊路径（APWP）中的“尖”或“发夹”（Channell，1996）似乎符合最近出版的“合成”非洲APWP（Besse and Courtillot，2002年）。但是，这两个APWP的定义不足以建立相干性或文件偏移，这意味着Adria和非洲之间的相对旋转。要解决这些问题，这项研究正在为关键的侏罗纪晚期侏罗纪至上的杂质间隔提供古磁性杆和非洲。 Adria（意大利）上的采样位点将使晚期侏罗纪白垩纪APWP的形状得到解决。将这些APWP与来自Gargano的APWP（认为不受推力板旋转影响）的比较，并可以确定ADRIA上其他地方的推力板旋转量。我们的研究为NW非洲提供了早期的白垩纪APWP，可以与极性地层相关，因此与地质时间尺度有关。这些数据将增加此时间间隔的非洲非常稀疏的数据，并与Adria的数据以及Besse and Courtillot（2002）的“合成”非洲APWP进行比较。 MAIO上层部分底部的插入式玄武岩和透明质物提供了一种将极性地层与绝对氩 - 阿尔贡同位素年龄联系起来的方法非洲自早期的中生代以来。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变至关重要。该项目已纳入佛罗里达大学的学习经验，学生将参与现场工作实验室的数据获取数据和结果分析。