Collaborative Research: Super-Plateau Breakup and Cretaceous Quiet Zone Tectonics

赤道以南近30%的太平洋板块形成于地球磁场异常稳定的时期。在这个白垩纪时期，onong - java - nui （OJN）火山喷发也发生了，形成了一个巨大的高原（地球面积的1/100），最终分裂。由于没有磁场反转来产生特有的地壳异常，从而使科学家能够跟踪构造板块运动，因此不可能理解这种深层火山活动与地表板块运动变化之间的因果关系。虽然卫星测量提供了海底结构的一些迹象，但不可能辨别出在控制高原分裂的快速扩张中心形成的狭窄的深海山丘。需要进行直接的海底测绘和采样。本科生和研究生将在本次研究中接受海洋地质数据采集方面的培训，部分学生将通过课堂项目参与巡航后的分析。研究研讨会的播客将扩展新知识的范围。OJN的破裂一定是通过奥斯本海槽的扩张而发生的，沿着埃利斯盆地未绘制的扩张中心。像其他早白垩纪海洋高原一样，OJN似乎是在一个三重交界处附近形成的。对白垩纪正常超时期太平洋构造的更好理解将有助于揭示海洋高原形成、分裂、板块重组以及与地幔柱的联系。此外，可以将来自超高原残迹的古纬度数据与一个共同的太平洋参考框架联系起来，以细化太平洋视极漂移路径，然后将其与印度-大西洋参考框架进行比较，以确定热点漂移和真极漂移的相对贡献。这是一项长期的工作，需要多学科研究者的多次考察和贡献。这项研究通过对埃利斯盆地的多波束调查迈出了这一过程的第一步，该调查将结合对这个大盆地中心部分的测绘，那里可能有灭绝的扩张中心，并且可以很容易地识别裂缝带的残余。结合选择性疏浚和玄武岩的氩定年，包括来自奥斯本海槽附近IODP站点U1365的样品，将有可能确定推断的扩展方向变化的时间，Ellice盆地扩展的终止，以及沿着奥斯本海槽的裂谷的结束。

Almost 30% of the Pacific plate south of the equator formed in a period where Earth's magnetic field was exceptionally stable. During this Cretaceous period, the Ontong-Java-Nui (OJN) volcanic outpouring also occurred, creating a large plateau (1/100 of Earth's area) that eventually split apart. With no reversals of the magnetic field to generate the characteristic crustal anomalies that allow scientists to track tectonic plate motions, it has not been possible to understand the cause-effect relation between this deep-generated volcanic activity and the change in plate motion at the surface. While satellite measurements provide some indication of seafloor structure, it is not possible to discern the narrow abyssal hills that form at the fast spreading centers that controlled the plateau breakup. Direct seafloor mapping and sampling are required. Undergraduate and graduate students will receive training in marine geological data acquisition during this study and some will participate in the post-cruise analysis via class projects. Podcasts of a research seminar will extend the reach of the new knowledge.The OJN breakup must have occurred via spreading at the Osbourn Trough, along unmapped spreading centers in the Ellice Basin. Like other early Cretaceous oceanic plateaus, the OJN seems to have formed near a triple junction. Better understanding of Pacific tectonics during the Cretaceous normal superchron should shed light on the connections between oceanic plateau formation, breakup, plate reorganizations and associations with mantle plumes. In addition, paleolatitude data from the super-plateau remnants can to be tied to a common Pacific reference frame to refine the Pacific apparent polar wander path, which could then be compared with the Indo-Atlantic reference frame to determine the relative contributions from hotspot drift and true polar wander. This is a long-term undertaking that will require several expeditions and contributions from multi-disciplinary investigators. This study takes the first step in this process with a multibeam survey of the Ellice Basin that will combine mapping of the central parts of this large basin where extinct spreading centers are likely to be located and remnants of fracture zones can be easily discerned. Coupled with selective dredging and Ar dating of basaltic rocks, including samples from IODP Site U1365 near Osbourn Trough, it will be possible to determine the timing of the inferred change in spreading direction, termination of Ellice Basin spreading, and the end of rifting along the Osbourn Trough.