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

剖析侏罗纪怪物极移：对埃塞俄比亚中晚侏罗世沉积岩的古地磁分析

• 批准号: 465492305
• 负责人: Dr. Edoardo Dallanave, Ph.D.
• 金额: --
• 依托单位: Fachgebiet Marine Geophysik
• 依托单位国家: 德国
• 项目类别: Research Grants
• 资助国家: 德国
• 项目状态: 未结题
• 来源: https://gepris.dfg.de/gepris/projekt/465492305?language=en
• 关键词: Dissecting; Jurassic; monster; polar; shift

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.

我们建议调查过去3亿年全球板块运动中最大、最快、研究最少的事件，这被称为“侏罗纪怪物极移”（跳变）。根据文献中关键古磁极的初步选择，从160到148 Ma，与大西洋和太平洋板块接壤的大陆同时围绕位于贝宁湾（西非近海）附近的一个共同赤道欧拉极顺时针旋转30°。世界上几个主要的沉积盆地在跨地带性气候带（如从高湿初级生产力的赤道带向高干低生产力的热带干旱带）转移时，通过调整沉积样式和结构来响应古纬度的相关变化。为现代科技世界提供燃料的一些最大的自然资源储存库可能就是这种运动的结果。在这个项目中，我们建议通过对亚的斯亚贝巴（埃塞俄比亚，非洲东北部）附近暴露的两个海洋沉积剖面的古地磁分析来调查和解剖跳跃（现在基于非常有限的数据清单）。该克拉通区是解决这一构造问题的理想地点，因为它自冈瓦纳破裂以来的纵向运动最小，与其他主要大陆区有板块-电路连接，并且存在扩展和完整的中-上侏罗统沉积剖面，可以提供高质量的古地磁数据。Mekele剖面和Mugher剖面的厚度分别为~660 m和~160 m，跨越了Bathonian和Tithonian之间的时间间隔，约为165 - 145 Ma，跨越了跳跃所包含的时间。共有9个地点将被取样进行古地磁分析。积极的结果将在整个跳变延伸区提供5个新的古磁极。采样地点的现有年龄将通过合作伙伴的古生物学分析加以完善。获得的古磁学数据集将采用先进的统计方法进行分析，这将大大提高其可靠性。所有获得的数据都必须合并到一个新的全球APWP中，以提供一个创新的跳跃视角。最终的结果将是创建一系列古地理地图，这些地图将包括项目中生成的所有约束条件。到目前为止，几乎所有发表的侏罗纪古地理重建图都没有包括跳跃的影响，因此是有缺陷的。本项目收集的古地磁数据将与欧拉极和各大洲的互反旋转的最新汇编相结合，以建立一个新的全球侏罗纪古地理，该古地理将在地球科学的几个学科中得到广泛应用。