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

合作研究：超级高原裂解与白垩纪静区构造

• 批准号: 1458444
• 负责人: Anthony Koppers
• 金额: $ 18.03万
• 依托单位: Oregon State University
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2016
• 资助国家: 美国
• 起止时间: 2016-09-01 至 2022-08-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=1458444&HistoricalAwards=false
• 关键词: Collaborative; Research; Super; Plateau; Breakup

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.

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，Ontong-Java-Nui（OJN）火山喷发也发生了，创造了一个大高原（地球面积的1/100），最终分裂。由于没有磁场的逆转来产生特征性的地壳异常，使科学家能够跟踪构造板块的运动，因此不可能理解这种深层岩浆的产生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，但无法辨别在控制高原分裂的快速扩张中心形成的狭窄深海丘陵。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采集方面的培训，有些学生将通过课堂项目参与巡航后分析。研究研讨会的播客将扩展新知识的范围。假设OJN断裂是通过在奥斯伯恩海槽的扩张发生的，沿着埃利斯盆地未绘制的扩张中心。像其他早白垩世的海洋高原一样，OJN似乎是在一个三联点附近形成的。更好地了解太平洋构造在白垩纪正常超时应阐明海洋高原的形成，解体，板块重组和协会与地幔柱之间的联系。此外，来自超高原遗迹的古纬度数据可以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正极移的相对贡献。理解OJN-linked过程的演变是一项长期任务。本研究在这一过程中迈出了第一步，对埃利斯盆地进行了多波束调查，将联合收割机对这个大盆地的中心部分进行测绘，在那里可能存在灭绝的扩张中心，断裂带的残余物可以很容易地辨别出来。再加上选择性疏浚和Ar测年的玄武质岩石，以及现有的样品从IODP网站U1365奥斯伯恩海槽附近，它将有可能确定推断的时间变化的扩展方向，终止埃利斯盆地扩展，并结束裂谷沿着奥斯伯恩海槽。