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.

该提案涉及阿德里亚(被亚得里亚海周边山脉环绕的大陆岩石圈)在阿尔卑斯山-地中海构造演化中的作用，这是一个30多年来一直争论的话题。“阿德里亚问题”涉及禤浩焯微板块表现为非洲板块的海角的观点。自那以后，这一想法得到了以前从Adria获得的古地磁数据的支持，尽管这个问题因Adria上沉积盖层的推力片旋转以及缺乏来自非洲和Adria的足够的古地磁数据而变得复杂。阿德里亚在侏罗纪和白垩纪的视极移路径(APWP)中的“尖点”或“发夹”(Channell，1996)似乎与最近发表的“合成”非洲APWP(Besse和Courtillot，2002)相吻合。然而，这两个APWP没有足够好的定义来建立一致性或文件偏移量，这意味着阿德里亚和非洲之间的相对旋转。为了解决这些问题，这项研究正在为阿德里亚和非洲的关键晚侏罗世-早期克里西期提供古地磁极。阿德里亚(意大利)上的采样点将使晚侏罗世-早白垩世APWP的形状得到解决。将这些APWP与加尔加诺的APWP(据信不受推力片旋转的影响)进行比较，可以确定阿德里亚其他地方的推力片旋转量。我们的研究正在为非洲西北部提供一个早白垩世APWP，它可以精确地与极性地层联系在一起，从而与地质时间尺度联系在一起。这些数据将增加这一时间间隔内非常稀少的非洲数据，并提供一种与Adria的数据以及与Besse和Courtillot(2002年)的“合成的”非洲平均升温潜能值进行比较的手段。马约远洋部分底部的夹层玄武岩和透明碎屑岩提供了一种将极性地层与绝对Ar-Ar同位素年龄联系起来的手段，以进行急需的时间刻度校准。我们的研究将确定自中生代早期以来，阿德里亚稳定的原地核是否相对于非洲发生了旋转。这个问题对阿尔卑斯山构造至关重要，因此对理解阿尔卑斯山带的演化也是至关重要的。该项目被整合到佛罗里达大学的学习经验中，学生将参与实地考察，实验室获取数据，并分析结果。