Early Permian Pangea 'B' to Late Permian Pangea 'A"
Early Permian Pangea 'B' to Late Permian Pangea 'A"
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DOI：
10.1016/s0012-821x(03)00452-7
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发表时间：
2003-10
影响因子：
5.3
通讯作者：
G. Muttoni;D. Kent;E. Garzanti;P. Brack;N. Abrahamsen;M. Gaetani
中科院分区：
文献类型：
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作者：
G. Muttoni;D. Kent;E. Garzanti;P. Brack;N. Abrahamsen;M. Gaetani
泛古陆漂移前的Wegenerian模型几乎被普遍接受，但自从Ted欧文根据古地磁数据将冈瓦纳大陆置于劳亚大陆以东约3000 km处，从而引入泛古陆“B”以来，其前侏罗纪构造仍存在争议。新的古地磁数据，从早二叠世火山岩的部分地区的亚德里亚，是与非洲（冈瓦纳）的构造一致，结合发表的同时代的数据，从冈瓦纳和劳亚，再次只有从火成岩，完全支持盘古大陆'B'配置在早二叠世。使用严格来自火成岩的古地磁数据排除了作为泛古陆“B”的解释的沉积倾斜误差。最终的选择，以拒绝盘古'B'是放弃地心轴向偶极子假说，通过引入一个显着的非偶极子（纬向八极）组成部分，在晚古生代时均地磁场。然而，我们证明，通过使用一个数据集完全由古地磁方向与低倾角仅限于一个半球从冈瓦纳大陆以及劳亚大陆的采样点，纬向八极场的贡献的影响不会解释古地磁证据盘古大陆'B'在早二叠世。因此，我们认为早二叠世盘古大陆“B”的古地磁证据是可靠的。从盘古大陆“B”到盘古大陆“A”的转变发生在二叠纪，因为晚二叠世的古地磁数据允许盘古大陆“A”的配置。因此，我们回顾地质证据的文献中支持的泛大陆内右旋巨震系统。这种转变发生在华力西巨型缝合线冷却之后，持续了2.2亿年。在此期间，新特提斯洋在印度/阿拉伯和东部的辛梅里亚微大陆之间打开，而广泛的岩石圈扭动和岩浆活动发生在亚得里亚海海角周围的西部。板块边界的一般分布和由此产生的驱动力是定性一致的冈瓦纳和劳亚大陆之间的右横向剪切对在二叠纪。与泛古陆转换相关的跨流板块边界重新激活了华力西剪切带，随后在侏罗纪被新特提斯海道西部的开放所利用。
The pre-drift Wegenerian model of Pangea is almost universally accepted, but debate exists on its pre-Jurassic configuration since Ted Irving introduced Pangea ‘B’ by placing Gondwana farther to the east by ∼3000 km with respect to Laurasia on the basis of paleomagnetic data. New paleomagnetic data from radiometrically dated Early Permian volcanic rocks from parts of Adria that are tectonically coherent with Africa (Gondwana), integrated with published coeval data from Gondwana and Laurasia, again only from igneous rocks, fully support a Pangea ‘B’ configuration in the Early Permian. The use of paleomagnetic data strictly from igneous rocks excludes artifacts from sedimentary inclination error as a contributing explanation for Pangea ‘B’. The ultimate option to reject Pangea ‘B’ is to abandon the geocentric axial dipole hypothesis by introducing a significant non-dipole (zonal octupole) component in the Late Paleozoic time-averaged geomagnetic field. We demonstrate, however, by using a dataset consisting entirely of paleomagnetic directions with low inclinations from sampling sites confined to one hemisphere from Gondwana as well as Laurasia that the effects of a zonal octupole field contribution would not explain away the paleomagnetic evidence for Pangea ‘B’ in the Early Permian. We therefore regard the paleomagnetic evidence for an Early Permian Pangea ‘B’ as robust. The transformation from Pangea ‘B’ to Pangea ‘A’ took place during the Permian because Late Permian paleomagnetic data allow a Pangea ‘A’ configuration. We therefore review geological evidence from the literature in support of an intra-Pangea dextral megashear system. The transformation occurred after the cooling of the Variscan mega-suture and lasted ∼20 Myr. In this interval, the Neotethys Ocean opened between India/Arabia and the Cimmerian microcontinents in the east, while widespread lithospheric wrenching and magmatism took place in the west around the Adriatic promontory. The general distribution of plate boundaries and resulting driving forces are qualitatively consistent with a right-lateral shear couple between Gondwana and Laurasia during the Permian. Transcurrent plate boundaries associated with the Pangea transformation reactivated Variscan shear zones and were subsequently exploited by the opening of western Neotethyan seaways in the Jurassic.