New high-quality paleomagnetic data from the Borborema Province (NE Brazil): Refinement of the APW path of Gondwana in the Early Cambrian
New high-quality paleomagnetic data from the Borborema Province (NE Brazil): Refinement of the APW path of Gondwana in the Early Cambrian
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DOI：
10.1016/j.precamres.2021.106243
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发表时间：
2021-05-10
影响因子：
3.8
通讯作者：
Tohver, Eric
中科院分区：
文献类型：
--
作者：
Jean Antonio, Paul Yves;Ferreira Trindade, Ricardo Ivan;Tohver, Eric
新元古代-古生代过渡（类似于541 Ma）是地球历史的转折点，导致微生物前寒武纪生命和埃迪卡拉生物革命之间发生巨大的生物变化，占领沉积基质，生物矿化的曙光和最早的多细胞生物的出现。与此同时，这一时期的特点是导致冈瓦纳大陆聚集的大规模板块重组和重大气候变化（极端冰川事件）。部分由于埃迪卡纪-寒武纪不同克拉通的古地磁数据库很差，当时的全球古地理仍然存在争议。在这项研究中，我们为 Borborema 省（巴西东北部）的 Monteiro 堤坝群提供了一个新的高质量古磁极（R = 7），位于南纬 18.2 度和东经 344.9 度（A95 = 11.7 度 K = 9.3）。它们是细粒角闪石辉绿岩，通过锆石上的 U-Pb 测年，年龄约为 538 Ma。岩石磁学数据表明磁铁矿和磁黄铁矿是主要的剩磁载流子。积极的烘烤接触测试支持了这些堤坝（19 个地点）获得的初级剩磁。 14个负倾向位点和5个正倾向位点也获得了阳性逆转测试（C类），表明古世俗变异已被消除。我们的新关键极点与冈瓦纳古陆的经典表观极地漂移路径不一致，冈瓦纳古陆由一条从大约 590 Ma 的南极位置到大约 520 Ma 的赤道位置的长轨迹组成，并且表明，在大约 100 秒的大型 IITPW 结束之后，APW 出现了快速而小幅的振荡。 560马。这些 TPW 据称是由内部质量重新分布导致的地球惯性张量变化引起的，与俯冲速度的快速变化有关。这些快速振荡和寒武纪辐射时间的联系对于了解动物生命的早期历史可能至关重要。
The Neoproterozoic-Paleozoic transition (similar to 541 Ma) was a turning point in Earth's history resulting in great biological changes between the microbial Precambrian life and the Ediacaran biotic revolution with the occupation of the sedimentary substrate, the dawn of biomineralization and the appearance of the earliest multicellular organisms. In parallel, this period is marked by a large plate reorganization leading to the assembly of Gondwana and by major climatic changes (extreme glacial events). Due in part to a poor paleomagnetic database for the different cratons in the Ediacarian-Cambrian times, the global paleogeography at that time remains controversial. In this study we present a new high-quality paleomagnetic pole (R = 7) for the Monteiro dyke swarm in the Borborema Province (NE Brazil) located at 18.2 degrees S and 344.9 degrees E (A95 = 11.7 degrees K = 9.3). They are fine-grained hornblende dolerite dated by U-Pb on zircon at similar to 538 Ma. Rock magnetic data indicate that magnetite and pyrrhotite are the main remanence carriers. Positive baked-contact tests support the primary remanence obtained for these dykes (19 sites). A positive reversal test (classified C) was also obtained from the 14 sites with negative inclination and the 5 sites with positive inclination, indicating that the paleosecular variation was eliminated. Our new key pole is not consistent with the classical apparent polar wander path of the Gondwana which consists of a long track from a southern polar position at similar to 590 Ma to an equatorial position at similar to 520 Ma, and suggests instead rapid and small oscillations of the APW, after the end of the large IITPW at ca. 560 Ma. These TPWs are supposedly caused by changes in the inertia tensor of the Earth due to internal mass redistribution, related to rapid changes in subduction velocity. Links of these rapid oscillations and the timing of the Cambrian radiation could be crucial to understand the early history of animal life.