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New high-quality paleomagnetic data from the Borborema Province (NE Brazil): Refinement of the APW path of Gondwana in the Early Cambrian
Precambrian Research ( IF 3.8 ) Pub Date : 2021-05-10 , DOI: 10.1016/j.precamres.2021.106243
Paul Yves Jean Antonio , Ricardo Ivan Ferreira Trindade , Bruno Giacomini , Daniele Brandt , Eric Tohver

The Neoproterozoic-Paleozoic transition (~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°S and 344.9°E (A95 = 11.7° K = 9.3). They are fine-grained hornblende dolerite dated by U-Pb on zircon at ~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 ~590 Ma to an equatorial position at ~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



中文翻译:

来自Borborema省(巴西东北部)的新高质量古磁数据:寒武纪初期冈瓦纳APW路径的细化

新元古代-古生代过渡(〜541 Ma)是地球历史上的转折点,导致微生物在前寒武纪生命与埃迪卡拉生物革命之间发生了巨大的生物学变化,其中包括沉积基质的占领,生物矿化的曙光和最早出现。多细胞生物。同时,这一时期的特点是大板块重组导致冈瓦纳的集结,以及主要的气候变化(极端冰川事件)。在一定程度上,由于埃迪亚-寒武纪时期不同克拉通的古地磁数据库不佳,当时的全球古地理学仍存在争议。在这项研究中,我们为位于Borborema省(巴西东北部)的Monteiro堤防群提供了一种新的高质量古磁极(R = 7),其位于南纬18.2°和东经344.9°(A95 = 11.7°K = 9.3)。它们是U-Pb在锆石上约538 Ma年代的细晶角闪石白云石。岩石磁数据表明,磁铁矿和黄铁矿是主要的剩磁载体。积极的烘烤接触测试支持了这些堤坝(19个部位)的主要剩磁。从14个负斜率位点和5个正斜率位点也获得了阳性逆转测试(分类C),这表明古目变化被消除了。我们的新关键极点与冈瓦纳的经典明显极地漂移路径不一致,该路径包括从约590 Ma的南极位置到约520 Ma的赤道位置的很长的轨迹,并暗示了该信号的快速且小幅度的振荡。 APW,大型IITPW结束后,岩石磁数据表明,磁铁矿和黄铁矿是主要的剩磁载体。积极的烘烤接触测试支持了这些堤坝(19个部位)的主要剩磁。从14个负斜率位点和5个正斜率位点也获得了阳性逆转测试(分类C),这表明古目变化被消除了。我们的新关键极点与冈瓦纳的经典明显极地漂移路径不一致,该路径包括从约590 Ma的南极位置到约520 Ma的赤道位置的很长的轨迹,并暗示了该信号的快速且小幅度的振荡。 APW,大型IITPW结束后,岩石磁数据表明,磁铁矿和黄铁矿是主要的剩磁载体。积极的烘烤接触测试支持了这些堤坝(19个部位)的主要剩磁。从14个负斜率位点和5个正斜率位点也获得了阳性逆转测试(分类C),这表明古目变化被消除了。我们的新关键极点与冈瓦纳的经典明显极地漂移路径不一致,该路径包括从约590 Ma的南极位置到约520 Ma的赤道位置的很长的轨迹,并暗示了该信号的快速且小幅度的振荡。 APW,大型IITPW结束后,积极的烘烤接触测试支持了这些堤坝(19个部位)的主要剩磁。从14个负斜率位点和5个正斜率位点也获得了阳性逆转测试(分类C),这表明古目变化被消除了。我们的新关键极点与冈瓦纳的经典明显极地漂移路径不一致,该路径包括从约590 Ma的南极位置到约520 Ma的赤道位置的很长的轨迹,并暗示了该信号的快速且小幅度的振荡。 APW,大型IITPW结束后,积极的烘烤接触测试支持了这些堤坝(19个部位)的主要剩磁。从14个负斜率位点和5个正斜率位点也获得了阳性逆转测试(分类C),这表明古目变化被消除了。我们的新关键极点与冈瓦纳的经典明显极地漂移路径不一致,该路径包括从约590 Ma的南极位置到约520 Ma的赤道位置的很长的轨迹,并暗示了该信号的快速且小幅度的振荡。 APW,大型IITPW结束后,约。560毫安。这些TPW可能是由于内部质量重新分布引起的地球惯性张量的变化而引起的,这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之间的联系对于了解动物生命的早期历史可能至关重要。

更新日期:2021-05-10
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