Neotectonic Evolution of Antarctic Peninsula/Scotia Sea Region: Multi-Beam, Sidescan Sonar, Seismic, Magnetics and Gravity Studies

该奖项支持对斯科舍海的布兰斯菲尔德海峡和沙克尔顿断裂带及其周边地区进行海洋地球物理调查，以了解该地区的新构造演化。多波束幅图和侧扫描声纳图将与多通道地震成像一起使用。本课题的主要目标是收集多波束和侧扫声纳数据，绘制西南斯科舍海、沙克尔顿断裂带和布兰斯菲尔德海峡板块边界演化的构造特征和构造结构。后续将在西南斯科舍海进行多通道地震调查。第二个目标是使用侧扫声纳反射率图像生成这些区域海底的详细结构图，并将新数据与现有的地震反射、Geosat重力、Hydrosweep和Seabeam测深数据相结合。一旦基础图生成，其他研究人员就可以使用它们来帮助解释多通道和单通道地震反射记录。南极半岛和斯科舍海的新构造演化极为复杂。了解德雷克-斯科舍-南极-南美洲板块交叉点的近期演变将提供重要信息，说明在一个长期存在的扩张中心消亡后，主要板块边界是如何重组的，以及随之而来的板块数量减少。板块重组可能导致沙克尔顿脊的隆升，从而影响了斯科舍海和威德尔海的沉积模式。如果在沙克尔顿转换断层与南美洲南端相交时，可以用多波束和侧扫声纳追踪断层的断裂，那么当转换断层与南美大陆相交时，断层的方向和几何形状、裂缝和变形将有助于解释该复杂地区的结构。基于高热流、活火山和地震反射工作的推断，布兰斯菲尔德海峡目前正在进行广泛的勘探。地震折射显示出类似东非裂谷或大陆被动火山边缘的厚地壳。相比之下，对最近火山的同位素和稀土元素的分析表明，似乎没有大陆污染。布兰斯菲尔德海峡的活动伸展肯定与板块重组有关，但目前尚不清楚究竟发生了什么构造过程。除了阐明布兰斯菲尔德海峡的构造结构外，多波束和侧扫声纳调查将确定潜在的疏浚目标和DSRV Alvin潜水点。

This award supports a marine geophysical investigation of the Bransfield Strait and the Shackleton Fracture Zone and environs in the Scotia Sea in an effort to understand the neotectonic evolution of the region. Multibeam swath mapping and sidescan sonar mapping will be used along with multichannel seismic imaging. The main goal of this proposal is to collect multibeam and sidescan sonar data to map the structural character and tectonic fabric of the evolving plate boundary in Southwest Scotia Sea, Shackleton Fracture Zone, and Bransfield Strait. Follow up multichannel seismic surveys will be done in the Southwest Scotia Sea. The secondary goal is to use sidescan sonar reflectivity images to generate detailed structural maps of the seafloor of these regions and to integrate the new data with existing seismic reflection, Geosat gravity, Hydrosweep and Seabeam bathymetric data. Once the base maps are produced they can be used by other researchers to help interpret multichannel and single channel seismic reflection records. The neotectonic evolution of the Antarctic Peninsula and Scotia Sea is extremely complex. Understanding the recent evolution of the Drake-Scotia-Antarctic-South America plate intersections will provide important information as to how major plate boundaries reorganize after demise of a long-lived spreading center and the consequential reduction in the number of plates. The plate reorganization probably resulted in the uplift of the Shackleton Ridge which may have effected the sedimentary patterns in both the Scotia Sea and possibly the Weddell Sea. If the break of the Shackleton transform fault can be traced with multibeam and sidescan sonar as it intersects the southern end of South America then the orientation and geometry of the faults, fractures and deformation as the transform fault intersects the South American continent will help to interpret the structures in that complex region. Bransfield Strait is presently undergoing extensi on based on high heat flow, active volcanoes and inferences from seismic reflection work. Seismic refraction indicates thick crust similar to the East African Rift or passive volcanic margins of continents. In contrast, analysis of isotopes and rare earth elements of the recent volcanics shows seemingly no continental contamination. The active extension in Bransfield Strait must be related to the plate reorganization but it is unclear exactly what tectonic processes are occurring. Besides elucidating the tectonic fabric of Bransfield Strait, the multibeam and sidescan sonar survey will identify potential dredge targets and DSRV Alvin dive sites.