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。在白垩纪期间，还发生了Ontong-Java-Nui(OJN)火山喷发，形成了一个大高原(占地球面积的1/100)，最终分裂开来。由于磁场没有发生逆转，从而产生了使科学家能够追踪构造板块运动的特征地壳异常，因此无法理解这种深部岩浆生成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广泛指示，但不可能辨别出在控制高原解体的快速扩张中心形成的狭窄的深海丘陵。需要更详细的海底测绘和取样。本科生和研究生将在本研究期间接受海洋地质数据获取方面的培训，一些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覆盖范围。据推测，OJN的分裂是通过在奥斯本海槽传播，沿着埃利斯盆地的未绘制的传播中心进行的。像其他早白垩世的海洋高原一样，OJN似乎是在一个三重结合部附近形成的。更好地了解白垩纪正常超时体期的太平洋构造，应该有助于揭示大洋高原形成、分裂、板块重组以及与地幔热柱之间的联系。此外，来自超高原残留物的古纬度数据可以绑定到一个共同的太平洋参考框架，以完善太平洋视极移路径，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移的相对贡献。了解OJN相关过程的演变是一项长期的任务。这项研究迈出了这一进程的第一步，对埃利斯盆地进行了多波束调查，这将结合这一大型盆地中央部分的地图，那里可能是灭绝的扩张中心所在，并很容易辨认出断裂带的残留物。结合对玄武岩的选择性挖掘和Ar测年，以及奥斯本海槽附近IODP地点U1365的现有样品，将有可能确定推断的扩散方向变化的时间、埃利斯盆地扩张的终止以及沿奥斯本海槽的裂谷作用的结束。

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 magmatic generation and the change in plate motion at the surface. While satellite measurements provide broad indication of seafloor structure, it is not possible to discern the narrow abyssal hills that would have formed at the fast spreading centers that controlled the plateau breakup. More detailed 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 post-cruise analysis via class projects. Podcasts of a research seminar will extend the reach of the new knowledge.The OJN breakup is hypothesized to 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 will then be compared with the Indo-Atlantic reference frame to determine the relative contributions from hotspot drift and true polar wander. Understanding evolution of OJN-linked processes is a long-term undertaking. 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, as well as existing 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.