Late Paleozoic Iberian Orocline(s) and the Missing Shortening in the Core of Pangea. Paleomagnetism From the Iberian Range
Late Paleozoic Iberian Orocline(s) and the Missing Shortening in the Core of Pangea. Paleomagnetism From the Iberian Range
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DOI：
10.1029/2018tc004978
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发表时间：
2018-10-01
期刊：
影响因子：
4.2
通讯作者：
Langereis, Cor G.
中科院分区：
文献类型：
--
作者：
Pastor-Galan, Daniel;Pueyo, Emilio L.;Langereis, Cor G.
超级大陆通常被解释为单一的刚性大陆板块。泛古陆是如何以及何时成为一个刚性超大陆存在争议，年龄估计从近似330到近似240 Ma不等。冈瓦纳-劳鲁西亚碰撞形成了华力西-阿列干尼亚带，这是泛大陆合并的最显著见证。在伊比利亚，该造山带以坎塔布里亚造山带和中伊比利亚曲线为特征，呈S形。中伊比利亚的弯曲在加利西亚-特拉斯-奥斯-蒙特斯和伊比利亚山脉的阿拉贡分支的趋势变化中尤为明显。最近的研究表明，这两个曲率不是同时代的，中央伊比利亚曲线必须形成之前，约。318 Ma（即，不是次级造山带）。我们报告了来自圣克鲁斯向斜（伊比利亚山脉的阿拉贡分支）古生代岩石的古地磁和构造结果，表明两个主要的垂直轴旋转事件：（1）新生代（阿尔卑斯山）顺时针旋转>20度和（2）晚石炭世逆时针旋转类似于70度。一旦新生代的旋转恢复，据称证明中伊比利亚曲线外弧的构造趋势变化就消失了。而新生代的旋转是不兼容的中伊比利亚曲线，晚石炭世的旋转是完全兼容的坎塔布连造山带，扩大受逆时针旋转和存在的非刚性泛古陆的影响，直到至少，类似于295马。然而，目前尚不清楚超级大陆何时达到其最终的刚性和坚固的形式。关于盘古大陆何时成为一个刚性超大陆存在争议;有些人认为它发生在3.3亿年前，而其他人则认为它发生在240年前。伊比利亚半岛见证了这一过程，今天，我们仍然可以看到当时形成的S形山脉遗迹。最近的研究表明，南北弯曲并不是同时形成的，南弯曲形成于318 Ma之前。我们报告古地磁和构造的结果，从古生代岩石的阿拉贡分支的伊比利亚山脉，表明趋势的变化，据称证据的南部曲线的S形是一个很晚的阿尔卑斯山构造的影响。总之，结果表明，盘古大陆至少在2.9亿年前才是刚性的。
Supercontinents are usually interpreted to be single and rigid continental plates. How and when Pangea became a rigid supercontinent is disputed, and age estimations vary from similar to 330 to similar to 240Ma. The Gondwana-Laurussia collision formed the Variscan-Alleghanian belt, the most prominent witness of Pangea's amalgamation. In Iberia, this orogen draws an S shape featured by the Cantabrian Orocline and the Central Iberian curve. The curvature of Central Iberia is particularly evident in Galicia-Tras-os-Montes and in a change of trend that it draws in the Aragonese Branch of the Iberian Range. Recent research showed that both curvatures are not coeval and that the Central Iberian curve had to form prior to ca. 318Ma (i.e., not a secondary orocline). We report paleomagnetic and structural results from Paleozoic rocks in the Santa Cruz syncline (Aragonese Branch of the Iberian Range) that indicate two main vertical axis rotations events: (1) a Cenozoic (Alpine) clockwise rotation of >20 degrees and (2) a late Carboniferous counterclockwise rotation of similar to 70 degrees. Once the Cenozoic rotation is restored, the change in structural trend that allegedly evidences the outer arc of the Central Iberian curve disappears. Whereas the Cenozoic rotation is incompatible with a Central Iberian curve, the late Carboniferous rotation is fully compatible with the Cantabrian Orocline, enlarging the area affected by its counterclockwise rotations and the existence of a nonrigid Pangea until, at least, similar to 295 Ma.Plain Language Summary Supercontinents like Pangea are thought to be rigid and stable in its interiors. It is not clear, however, when the supercontinents achieve its final rigid and sturdy form. There is a debate on when Pangea became a rigid supercontinent; some people argue that it happened as soon as 330 million years ago and others as recently as 240. The Iberian peninsula witnessed all this process, and today, we still can see the relic of the mountain range formed at that time with an S shape. Recent research showed that both north and south curvatures did not form coevally and that the southern curve formed before 318 Ma. We report paleomagnetic and structural results from Paleozoic rocks in the Aragonese Branch of the Iberian Range that indicate that the change in trend that allegedly evidences the southern curve of this S shape is a much later effect of Alpine tectonics. Altogether, the results show that Pangea was not rigid until at least 290 million years ago.