Integrated Geophysical and Geologic Investigation of the Crustal Structure of Western Canada Basin, Chukchi Borderland and Mendeleev Ridge, Arctic Ocean

加拿大西部盆地、楚科奇边境和北冰洋门捷列夫海岭地壳结构综合地球物理和地质调查

• 批准号: 0327626
• 负责人: Lawrence Lawver
• 金额: --
• 依托单位: University of Texas at Austin
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2004
• 资助国家: 美国
• 起止时间: 2004-05-01 至 2008-12-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=0327626&HistoricalAwards=false
• 关键词: Integrated; Geophysical; Geologic; Investigation; Crustal

Intellectual merit: The Principal Investigators will undertake an integrated geophysical and geological study of the western section of the Amerasian Basin of the Arctic Ocean to include: determining the crustal structure of the deepCanada Basin, Northwind Ridge, Chukchi Borderland, Chukchi Basin, and Mendeleev Ridge; collectingseismic reflection data to determine depositional history and locate potential drill sites; and taking pistoncores to define the sedimentary history of the region. Regional geologic studies, seismic reflectionprofiling from conventional geophysical vessels along the periphery of the Arctic Basin and fromicebreakers within the polar ice pack, aerogeophysics, and satellite altimetry data have led manyresearchers to support the idea that the Amerasia Basin of the Arctic Ocean opened about a pivot point nearthe Mackenzie Delta. Simple reconstruction of the Amerasia Basin is precluded, however, by the presenceof the Chukchi Borderland, an extensive cluster of submarine plateaus in the Amerasia Basin north of theChukchi shelf, and by Mendeleev Ridge. If both the Borderland and the Alpha/Mendeleev Ridge areconstructed of igneous rocks that postdate opening of the Amerasia Basin, simple closure is not a problem.However, Grantz and others have cored Phanerozoic sediments, including Cambrian andOrdovician shallow-water marine carbonates from Northwind Ridge that are similar to the basement rocksfound beneath the Sverdrup basin of the Canadian Arctic Archipelago. If Chukchi Borderland consists ofcontinental crust, complicated tectonic scenarios must be devised to explain its presence. The crustalcharacter of the Borderland is therefore critical to understanding the origin and kinematics of the AmerasiaBasin's opening. Northwind Ridge, the easternmost plateau of the Chukchi Borderland, faces the EarlyCretaceous Canada Basin (the largest and deepest part of the Amerasia Basin) at Northwind Escarpment.The escarpment is a distinctive feature invoked in many tectonic models for the opening of the AmerasiaBasin. Because Northwind Ridge is a high-standing plateau that adjoins the tectonically enigmaticNorthwind Escarpment, understanding the crustal character of the Chukchi Borderland and the contrastbetween it and that of the deep Canada Basin is very important. Virtually nothing is known of the crustalstructure and seismic stratigraphy of Mendeleev Ridge. They will conduct a seismic reflection andrefraction experiment to resolve fundamental questions concerning the tectonic evolution of the AmerasiaBasin. Cross tracks from the deeper Canada Basin across the Northwind Ridge should determine whetherit has operated as a transform margin, convergent margin or neither. Understanding the evolution of theCanada Basin and its development as a deep-water basin is fundamental to such basic concerns as sea levelfluctuations and paleoclimate in the Mesozoic. The experiment will require building 25 sea-ice seismometers [SIS] that will be deployed on the ice using the U.S. Coast Guard (USCG) helicopters. The hydrophone of the SIS will be deployed through a hole augered through the ice. Radio transmitters will allow monitoring of the arrival data on board so that the SISs canbe retrieved as soon as the refracted arrivals are observed. A global positioning system (GPS) unit in the SIS will provide continuous location. A basic arrival time versus offset analysis of real-time data will provide key information requiredfor a fast interpretation of the crustal structure of the Chukchi Borderland and the Mendeleev Ridge. Thedata will also be used in iterative travel-time tomographic inversions to delineate details of the velocity structure. The velocity structure will be used in conjunction with existing seismic reflection and geologic data to produce complete crustal sections of Chukchi Borderland, Chukchi Basin and Mendeleev Ridge. The resulting crustal sections will be used to calibrate existing ship, satellite, submarine and aerogravity data, to construct realistic models, and to address such questions as the tectonic origin and degree of extension in the Chukchi Borderland, the origin of Mendeleev Ridge, and todetermine whether there has been convergence between Northwind Ridge and Canada Basin.Broader Impacts: The Principal Investigators will include at least four crossed lines suitable for siting future drillingoperations in the region. The IODP drill sites will be used to study the climate history of the Arctic region,ocean circulation patterns, and impact of ice-covered versus ice-free conditions on the biotic evolution ofthe Arctic. Determination of the crustal structure of both Chukchi Borderland and Mendeleev Ridge hasimportant implications for Law of the Sea considerations. Three graduate students and a minimum number of two undergraduates will be recruited to participate in this cruise.

智力优点：主要调查员将对北冰洋美亚海盆西段进行综合地球物理和地质研究，包括：确定加拿大海盆、北风海岭、楚科奇边界、楚科奇海盆和门捷列夫海岭的地壳结构;收集地震反射数据，以确定沉积历史和确定潜在钻井地点;取活塞岩心，确定该区的沉积史。区域地质研究、沿沿着北极盆地周边的常规地球物理船和极地冰盖内的碎冰船的地震反射剖面、航空地球物理学和卫星测高数据，使许多研究人员支持北冰洋的美亚盆地在靠近麦肯齐三角洲的一个支点附近打开的观点。然而，由于楚科奇边界和门捷列夫海岭的存在，排除了对美亚海盆进行简单重建的可能性。楚科奇边界是美亚海盆中楚科奇大陆架以北的一个广阔的海底高原群。如果边境地带和阿尔法/门捷列夫海岭都是由美亚海盆开启之后的火成岩构成的，那么简单的闭合就不成问题。然而，格兰茨和其他人已经取了古生代沉积物的岩心，包括来自北风海岭的寒武纪和奥陶纪浅水海洋碳酸盐岩，它们与加拿大北极群岛斯维尔德鲁普海盆下发现的基底岩石相似。如果楚科奇边界是由大陆地壳组成的，那么必须设计复杂的构造情景来解释它的存在。因此，边缘地带的地壳特征对于理解美亚海盆开口的起源和运动学至关重要。Northwind Ridge是楚科奇边界最东端的高原，在Northwind Escarpment面对早白垩世加拿大盆地（Amerasia Basin最大和最深的部分）。由于Northwind Ridge是一个高海拔高原，毗邻构造上神秘的Northwind Escarpment，因此了解楚科奇边界的地壳特征及其与加拿大盆地深部的对比非常重要。门捷列夫海岭的地壳结构和地震地层学几乎一无所知。 他们将进行地震反射和折射实验，以解决有关美亚盆地构造演化的基本问题。从加拿大海盆较深处穿过北风脊的交叉轨迹应该决定它是否作为转换边缘、会聚边缘或两者都不是。了解加拿大海盆的演化及其作为深水海盆的发展，对于了解中生代海平面波动和古气候等基本问题至关重要。该实验将需要建造25个海冰地震仪（SIS），这些地震仪将使用美国海岸警卫队（USCG）直升机部署在冰上。SIS的水听器将通过在冰中钻一个洞来部署。无线电发射机将允许监测船上的到达数据，以便一旦观察到折射到达，就可以检索SIS。SIS中的全球定位系统将提供连续定位。对实时数据的基本到达时间与偏移距的分析将为快速解释楚科奇边界和门捷列夫海岭的地壳结构提供关键信息。这些数据也将用于迭代旅行时层析反演，以描绘速度结构的细节。速度结构将与现有的地震反射和地质数据结合使用，以制作楚科奇边界、楚科奇盆地和门捷列夫海岭的完整地壳剖面。由此产生的地壳剖面将用于校准现有的船舶、卫星、潜艇和空气重力数据，构建真实的模型，并解决诸如楚科奇边界地区的构造起源和延伸程度、门捷列夫海岭的起源等问题，并确定北风海岭和加拿大海盆之间是否存在会聚。主要调查人员将包括至少四条交叉线，适合在该地区定位未来的钻井作业。IODP钻探地点将用于研究北极地区的气候历史、海洋环流模式以及有冰和无冰条件对北极生物进化的影响。 确定楚科奇边界和门捷列夫海脊的地壳结构对海洋法的审议具有重要意义。将招募三名研究生和至少两名本科生参加这次航行。