An integrated geophysics cruise to map the northern edge in the Chukchi Borderland and the adjacent Canada Basin - constraints on basin history and crustal structure

在过去的50年里，我们了解到海洋盆地相对年轻。了解它们的历史对于了解古老的相邻大陆是必要的。北冰洋的亚美亚盆地是个谜。虽然它是一个海洋盆地，但海底扩张造成的熟悉模式并不明显。因此，不可能了解盆地的历史。该项目将研究Amerasia盆地三个相邻特征的历史：Chukchi Borderland、Alpha Ridge和Canada Basin。该项目计划在一艘研究船上使用丹麦和格陵兰地质调查局（GEUS）便携式、灵活的多通道地震反射（MCS）系统。该系统已在厚浮冰中成功运行，将收集MCS数据，用于地层和构造解释，并为全地壳折射工作提供足够的震源强度。利用海底地震仪（OBS）将在加拿大盆地的两个地点获得较强的深部地壳结构约束。在MCS剖面过程中，声纳浮标也将获得折射数据，并将用于模拟上部地壳结构。对这些数据的收集和分析将提供关于美亚西亚盆地形成的新知识，并提高我们对欧亚大陆东北部和北美西北部历史的理解。该项目还将有助于培养新一代北极海洋地球科学家，支持科学海洋钻探，对海底以下的沉积物进行采样，并帮助确定美国在北冰洋的领土范围。在很大程度上，目前对美亚拉盆地的了解是基于对邻近大陆的观察和对形成该盆地的构造位移的假设。一种基于在相邻特征之间建立关键关系的新方法，将使通过扩大局部关系来重建海洋的构造历史成为可能。楚科奇陆缘是嵌于深水美亚盆地中的一块伸展大陆地壳。为了认识盆地的张开，有必要将边缘地带恢复到张开前的位置。这个位置的选择区分了盆地的构造模式，这些模式没有很好地受到观测的约束。在之前的工作中，一项横跨楚科奇陆架到边界地过渡的2 MCS调查表明，自早白垩纪以来，在这一边界上只有轻微的位移。下一步是了解主要来自水深数据的边疆北部边缘的结构和历史。在这个地区，亚美亚盆地的三个主要构造相交：边界地带、阿尔法岭和加拿大盆地。在该地区进行专门的MCS调查将提高我们对这些结构的理解，以及它们在北部和东部沉积物覆盖下的终止或延续。在这个项目中，MCS和折射测量将阐明明显的大陆、高位块体和周围地壳之间的关系，这些地壳可能也是大陆成分的一部分。对楚科奇边界北缘及邻近深水区的观测，将通过区分地壳类型，对美亚西亚盆地的历史提供新的约束。该奖项反映了美国国家科学基金会的法定使命，并通过使用基金会的知识价值和更广泛的影响审查标准进行评估，被认为值得支持。

Over the last fifty years, we have learned the ocean basins are relatively young. Knowing their history is necessary to understand the ancient, adjacent continents. The Amerasia Basin of the Arctic Ocean is a mystery. While it is an ocean basin, the familiar patterns created by seafloor spreading are not obvious. As a result, it has not been possible to understand the basin history. This project will study the history of three adjacent features in the Amerasia Basin: the Chukchi Borderland, the Alpha Ridge and the Canada Basin This project plan to use the Geological Survey of Denmark and Greenland (GEUS) portable, flexible multi-channel seismic reflection (MCS) system on a research vessel. This system, which has been successfully operated in thick pack ice, will collect MCS data, for stratigraphic and structural interpretation, and provide sufficient source strength for full crustal refraction work. Stronger constraint on the deep crustal structure will be obtained in two locations in the Canada Basin with ocean bottom seismometers (OBS). Refraction data will also be acquired with sonobuoys during MCS profiling and will be used to model upper crustal structure. The collection and analysis of the data will provide new knowledge about the formation of the Amerasia Basin and improve our understanding of the history of northeast Eurasia and northwest North America. This project will also help educate a new generation of Arctic marine geoscientists, support scientific ocean drilling to sample the sediments below the seafloor and help define the extent of US territory in the Arctic Ocean. For the most part, current understanding of the Amerasia Basin is based on observations made on the adjacent continents and an assumption about the tectonic displacements that formed the basin. A new approach based on establishing critical relationships between adjacent features will make it possible to recreate the tectonic history of the ocean by scaling up from local relationships. The Chukchi Borderland is a block of extended continental crust embedded in the deep water Amerasia Basin. To understand the basin opening, it is necessary to restore the Borderland to its pre-opening position. The choice of this position distinguishes tectonic models of the basin which are not well constrained by observations. In previous work, a 2- MCS survey across the transition from the Chukchi Shelf to Borderland established that there have been only slight displacements across this boundary since Early Cretaceous. Understanding the structure and history of the northern edge of the Borderland, known primarily from bathymetric data, is the next step. In this area, three of the major structures of the Amerasia Basin intersect: the Borderland, Alpha Ridge and the Canada Basin. A dedicated MCS survey in this area will improve our understanding of these structures and their termination or continuation below the sediment cover to the north and east. In this project, MCS and refraction surveys will elucidate the relations between the overtly continental, high-standing block and the surrounding crust, which may be, in part, of continental composition as well. Observing the northern edge of the Chukchi Borderland and adjacent deeper water areas will, by distinguishing crustal types, provide new constraints on the history of the Amerasia Basin.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.