Dissecting the Jurassic monster polar shift: Paleomagnetic analyses of Middle–Late Jurassic sedimentary rocks from Ethiopia

我们打算调查过去3亿年来全球板块运动中规模最大、速度最快、研究最少的事件，即侏罗纪怪物极移(JUPS)。根据从文献中初步选择的关键古地磁极，在160~148 Ma期间，与大西洋和太平洋板块接壤的大陆围绕位于贝宁湾(西非近海)附近的一个共同的赤道欧拉极同时顺时针旋转30°。世界各地的几个主要沉积盆地在跨越地带性气候带时，例如从高湿度和初级生产力的赤道带转移到高干旱和低生产力的热带干旱带，通过调整其沉积风格和结构来应对与之相关的古纬度变化。为现代科技世界提供燃料的一些最大的自然资源蓄水池可能就是这项动议的结果。在这个项目中，我们建议通过对亚的斯亚贝巴(埃塞俄比亚，东北部非洲)附近暴露的两个海洋沉积剖面进行古地磁分析来调查和剖析跳跃(目前基于非常有限的数据清单)。该克拉通地区是解决这一构造问题的理想地点，因为其自冈瓦那断裂以来最小的纵向运动，与其他主要大陆地区的板块电路连接，以及存在扩大和完整的中上侏罗世沉积剖面，可以提供高质量的古地磁数据集。两个目标剖面，即Mekele段和Mugher段，分别厚约660m和~160m，横跨巴东纪和泰山纪之间的时间间隔，约165~145 Ma，跨越了跳跃所包含的时间。总共将对9个地点进行古地磁分析。积极的结果将在整个跳跃范围内提供5个新的古地磁极。采样遗址的现存年龄将通过对合作伙伴的古生物分析来精炼。获取的古地磁数据集将采用尖端统计方法进行分析，这将显著提高其可靠性。所有获得的数据都必须合并到一个新的全球APWP中，以提供跳跃的创新视角。最终结果将是创建一系列古地理地图，其中将包括项目内产生的所有约束。到目前为止，我们用于侏罗纪的几乎所有已发表的古地理重建都不包括跳跃的影响，因此是有缺陷的。该项目检索的古地磁数据将与所有大陆的欧拉极和相互自转的最新汇编相结合，以建立新的全球侏罗纪古地理，这将在地球科学的几个学科中广泛使用。

We propose to investigate the largest, fastest, and least studied event of global plate motion of the last 300 million years, which is referred to as the ‘Jurassic monster polar shift’ (JUMPS). According to a preliminary selection of key paleomagnetic poles from the literature, from 160 to 148 Ma the continents bordering the Atlantic and the Pacific plate underwent a simultaneous clockwise rotation of 30° around a common equatorial Euler pole located near the Bay of Benin (offshore west Africa). Several major sedimentary basins worldwide responded to the associated changes in paleolatitude by adjusting their depositional style and architecture when shifting across zonal climate belts, for example from the equatorial belt of high humidity and primary productivity to the tropical arid belts of high aridity and low productivity. Some of the vastest reservoirs of natural resources that fuel the modern technological world may have originated as consequence of this motion. In this project, we propose to investigate and dissect the JUMPS (now based on a very limited data inventory) by means of paleomagnetic analyses of two marine sedimentary sections exposed near Addis Ababa (Ethiopia, North-east Africa). This cratonic area is an ideal locus for solving this tectonic problem because of its minimal longitudinal movement since Gondwana breakdown, plate-circuit-connection with the other major continental area, and presence of expanded and complete Middle-Upper Jurassic sedimentary sections that can provide high quality paleomagnetic dataset. The two target sections, namely the Mekele section and the Mugher section, are respectively ~660 m and ~160 m thick, and span a time interval between the Bathonian and the Tithonian, from about 165 to 145 Ma, straddling the time encompassed by the JUMPS. A total of 9 sites will be sampled for paleomagnetic analyses. Positive results will provide 5 new paleomagnetic poles across the whole extension of the JUMPS. The existing age of the sampled sites will be refined by paleontological analyses of cooperating partners. The acquired paleomagnetic dataset will be analyzed with cutting-edge statistical methods, which will significantly increase its reliability. All acquired data will have to be merged into a new global APWP in order to provide an innovative perspective of the JUMPS. The final result will be the creation of a series of paleogeographic maps that will include all constraints generated within the project. Up to date, virtually all published paleogeographic reconstructions that we use for the Jurassic do not include the effects of the JUMPS, and are therefore flawed. The paleomagnetic data retrieved in this project will be combined with the most recent compilation of Euler poles and reciprocal rotations for all continents in order to build a new global Jurassic paleogeography that will be of wide use in several disciplines of Earth Sciences.