Testing Pangea Reconstructions with New Late Permian - Early Triassic Paleomagnetic Studies

用新的晚二叠世-早三叠世古地磁研究测试盘古大陆重建

• 批准号: 0634807
• 负责人: Rob Van der Voo
• 金额: --
• 依托单位: Regents of the University of Michigan - Ann Arbor
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2007
• 资助国家: 美国
• 起止时间: 2007-04-01 至 2011-03-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=0634807&HistoricalAwards=false
• 关键词: Testing; Pangea; Reconstructions; New; Late

Pangea, as it existed in late Paleozoic and early Mesozoic time, consisted of a northern group of continents (Laurasia, comprised of North America, Greenland, Europe and Asia) and the southern Gondwana assembly, which includes South America, Africa, Australia, Madagascar, India, and Antarctica. It is generally assumed that in Pangea, Gondwana's Northwest-African margin was adjacent to North America's Appalachian margin; this reconstruction is called Pangea-A. However, for times before the Late Triassic the available data from paleomagnetism derived from Gondwana and Laurasia do not agree well with the Pangea-A fit, which have led scientists to either question the validity of these data or to propose a different fit, called Pangea-B. The main problem with the Pangea-B reconstruction is that everyone agrees that by Late Triassic time, the fit was that of Pangea-A, which implies that Pangea-B transformed into Pangea-A in Permian or Triassic time. The relative movements to accomplish this change consist of a surprisingly large 3500-km or greater dextral mega-shear between Gondwana and Laurasia. For such a mega-shear, little geological evidence exists, and geologists have therefore ignored the Pangea-B proposal. Relevant Late Permian and Early Triassic paleomagnetic data have thus far remained of demonstrably inferior quality, and we intend, therefore, to collect new paleomagnetic data for this time interval to test Pangea fits, and to determine whether a change from Pangea-B to Pangea-A occurred before or after the Late Permian, if it did occur at all. The majority of the new collections will be from Argentina, where stratified volcanic rocks exist that will likely yield reliable results. The supercontinent Pangea is a very fundamental and prominent aspect of the ancient geography of the Earth, and the accuracy of its configuration is of interest to anyone studying Earth Science. The aim of this study is to determine whether there is any evidence for a Pangea reconstruction in Late Permian-Early Triassic paleomagnetic data, in which northwestern South America was located adjacent to the Appalachian margin of North America. Such a Pangea-B reconstruction is rather different from the classically and widely accepted Pangea-A fit in which northwestern South America is, instead, adjacent to the Texas margin of North America. The available paleomagnetic records for Permian and Early Triassic time surprisingly seem to favor Pangea-B, which has puzzled geologists for decades. If Pangea B existed, then it must have undergone a large wrenching movement during either the Permian or the Triassic. This study intends to establish whether the previous, rather preliminary results that favor Pangea-B are supported by carefully determined new paleomagnetic data. If Pangea-B is found to have existed, the study will by inference have obtained evidence for enormous lateral fault movements, of the order of 3500 km in length or more, the likes of which are not documented for any time in the post-Pangea history of the Earth, that is, in the last 200 million years.

Pangea在古生代晚期和中生代早期存在，由北部大陆（劳拉西亚（Laurasia）组成，包括北美，格陵兰岛，欧洲和亚洲）和南部冈瓦纳大会，其中包括南美，非洲，非洲，澳大利亚，澳大利亚，马达加斯加斯加邦，印度，印度，印度和南方群岛。通常认为，冈瓦纳（Gondwana）的西北 - 非洲边际利润与北美的阿巴拉契亚边缘相邻。这种重建称为pangea-a。然而，在晚期三叠纪之前，来自冈瓦纳和劳拉西亚的古磁性数据与pangea-a拟合不太吻合，这导致科学家质疑这些数据的有效性，或者提出了不同的拟合度，称为pangea-b。 Pangea-B重建的主要问题是，每个人都同意，到后期三叠纪的时间，Pangea-A的契合度是Pangea-B在二叠纪或三叠纪时间中转变为Pangea-a。实现这一变化的相对动作包括出奇的大型3500公里或更大的巨麦剪切，在冈瓦纳和劳拉西亚之间。对于这样的巨型剪切，几乎没有地质证据，因此地质学家忽略了Pangea-B的提议。到目前为止，相关的晚期二叠纪和早期三叠纪的古磁数据仍然具有明显的质量，因此我们打算在此时间间隔内收集新的古磁数据，以测试Pangea拟合，并确定是否发生了从Pangea-B到Pangea-A发生的变化，是否发生在晚期或之后发生在晚期的情况下发生。大多数新收藏品将来自阿根廷，那里存在分层的火山岩，可能会产生可靠的结果。超大型的pangea是地球古代地理的一个非常基本和突出的方面，其配置的准确性对于研究地球科学的任何人都有意义。这项研究的目的是确定是否有任何证据表明在晚期二叠纪三叠纪的古磁数据中是否有pangea重建，其中南美西北部位于北美阿巴拉契亚缘附近。这种pangea-b的重建与古典和广泛接受的pangea-a拟合，而南美西北部与北美德克萨斯州边际相邻。二叠纪和早期三叠纪时间的可用古磁记录令人惊讶地支持Pangea-B，这使地质学家困惑了数十年。如果存在Pangea B，那么在二叠纪或三叠纪期间，它一定会发生巨大的扭动运动。这项研究旨在确定先前确定的新古磁数据支持先前的，有利于Pangea-B的初步结果。如果发现Pangea-B存在，则该研究将通过推断获得了巨大的侧向断层运动的证据，其长度为3500 km或更长时间，在地球后的庞格历史上，该研究的任何时间都没有记录在过去的20000年中。