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

该提案解决了亚德里亚（亚得里亚海周围山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，这一问题已经争论了30多年。“亚德里亚问题”涉及到亚德里亚微板块作为非洲板块的一个海角的观点。这一观点得到了先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板旋转以及非洲和亚德里亚缺乏足够的古地磁数据而变得复杂。亚德里亚的侏罗纪和白垩纪表观极移路径（APWP）中的“尖峰”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的定义不够明确，无法建立一致性或记录偏移量，从而意味着亚德里亚和非洲之间的相对旋转。为了解决这些问题，本研究在亚德里亚和非洲提供了晚侏罗世-早白垩纪关键时期的古磁极。亚德里亚（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进行比较（据信不受推力片旋转的影响），可以确定亚德里亚其他地方推力片旋转的数量。我们的研究为西北非洲提供了一个早白垩世的APWP，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。这些数据将增加这段时间间隔内非常稀疏的非洲数据，并提供与来自亚德里亚的数据以及Besse和Courtillot（2002）的“合成”非洲APWP进行比较的手段。迈奥岛上层剖面底部的插层玄武岩和透明质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，用于急需的时间刻度校准。我们的研究将确定早中生代以来亚德里亚的稳定原生核是否相对于非洲进行了旋转。这个问题对阿尔卑斯构造学至关重要，因此对了解阿尔卑斯带的演化也至关重要。该项目被整合到佛罗里达大学的学习经验中，学生将参与实地工作，在实验室获取数据，并分析结果。

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.