The Bransfield Strait-South Shetland Islands/Trench: Structural and Stratigraphic Evolution of a Linked(?) Back-arc/Fore-arc System

布兰斯菲尔德海峡-南设得兰群岛/海沟：关联的（？）弧后/弧前系统的结构和地层演化

• 批准号: 9418135
• 负责人: Ian Dalziel
• 金额: $ 5.93万
• 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: 1995
• 资助国家: 美国
• 起止时间: 1995-02-15 至 1997-07-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=9418135&HistoricalAwards=false
• 关键词: Bransfield; Strait; South; Shetland; Islands

Abstract This award supports a geophysical study of the Bransfield Strait region of Antarctica using recently collected multichannel seismic data. University of Texas Institute of Geophysics (UTIG) multichannel seismic (MCS) data (EW91-01 data) has enabled detailed analysis of structural style and rifting processes in Bransfield Strait to be carried out. The analysis has brought new insight to the ongoing extensional processes in Bransfield Strait. This project will build on this work to consider Bransfield Strait in the full context of a fore-arc/back-arc tectonic system. This project will primarily use UTIG (EW91-01) MCS data, but will also incorporate other geophysical data from the region that are available from the United Kingdom and Italy. Bransfield Strait is a young basin apparently undergoing active (intracontinental?) extension located between the Antarctic Peninsula and the South Shetland Islands, a small chain of islands to the northwest trending roughly parallel with the Peninsula. Although the South Shetland Islands show no recent arc volcanism, they lie above a subduction zone which still appears to be active, albeit with subduction occurring at a slow rate. This tectonic setting and interpretation of other events affecting plate motions in the vicinity have lead to the currently-held view that Bransfield Strait has opened as a backarc basin in response to South Shetland Trench roll-back or retreat. However, the modern stress regime is unclear. The focus of study thus far has been on the structural style and rifting processes observed in recently-acquired UTIG (EW91-01) MCS data in Bransfield Strait. Initial seismic interpretation indicates that intracrustal diapirism, as evidenced by faulting of overlying sediment and associated high-amplitude seismic events, may be an important element of observed extension. Besides the significance of this diapirism with respect to active rifting processes, it also has implications regarding the evolutio n of the extensional stress regime in Bransfield Strait. It is possible that transtensional tectonics to the northeast of the Strait are increasingly important relative to trench rollback in driving extension in the Strait. This project will consolidate the geophysical analysis of Bransfield Strait and build upon it by considering the Strait's relationship with the adjacent South Shetland Trench and "forearc". EW91-01 MCS data are ideally suited to an analysis of whether structures seen in the "back-arc" relate to structures and processes at the trench and "fore- arc". A key part of this analysis will be to test the hypothesis that trench roll-back is causing "back-arc" extension in Bransfield Strait. High quality MCS data from Italy and the United Kingdom will be integrated with the EW91-01 MCS data for more comprehensive areal coverage and seismic analysis of structural style in the "back-arc" and `fore-arc". EW91-01 potential field data will also be incorporated in the study. Comparison of the northern Antarctic peninsula with other regions characterized by similar, though not necessarily identical, active tectonic settings (e.g., Lau Basin, Gulf of California) should allow an estimate of the relative importance of processes of marginal basin formation and evolution on global versus local scales. Furthermore, the common history that the Antarctic Peninsula Pacific margin shares with the South American Pacific margin as parts of the convergent plate margin of Gondwanaland means that Bransfield Strait can be considered a modern analog for Early to mid-Cretaceous evolution of the Rocas Verdes marginal basin of southern Chile. The Rocas Verdes Basin history is critical to understanding early stages of Andean orogenesis.

摘要该奖项支持最近收集的多通道地震数据对南极洲布兰斯菲尔德海峡区域进行的地球物理研究。 德克萨斯大学地球物理学院（UTIG）多通道地震（MCS）数据（EW91-01数据）已实现了Bransfield海峡的结构样式和裂谷过程的详细分析。 该分析为布兰斯菲尔德海峡正在进行的扩展过程带来了新的见解。 该项目将以这项工作为基础，以在前弧/背面弧形系统的完整背景下考虑布兰斯菲尔德海峡。 该项目将主要使用UTIG（EW91-01）MCS数据，但还将合并来自英国和意大利可获得的该地区的其他地球物理数据。 布兰斯菲尔德海峡（Bransfield Strait）是一个年轻的盆地，显然正在南极半岛和南设得兰群岛之间的活跃（肠内？）延伸，这是一小群岛屿到西北的岛屿，趋势与半岛大致相似。 尽管南设得兰群岛没有显示最近的弧形火山，但它们位于俯冲带上，尽管俯冲速度以缓慢的速度出现，但它似乎仍然活跃。这种影响附近板块动作的其他事件的构造环境和解释导致目前控制的观点是，布兰斯菲尔德海峡已经作为后巴克盆地开放，以响应南开兰州的沟槽后卫或务虚会。 但是，现代压力制度尚不清楚。 迄今为止，研究重点是在布兰斯菲尔德海峡（Bransfield Strait）最近获得的UTIG（EW91-01）MCS数据中观察到的结构样式和裂谷过程。 最初的地震解释表明，在上面的沉积物和相关的高振幅地震事件的断层中证明，围内遗传学可能是观察到的扩展的重要组成部分。除了这种遗传学对主动裂谷过程的重要性外，它还对布兰斯菲尔德海峡伸展应力状态的进化也有影响。相对于海峡驱动延伸时，海峡东北部向东北的旋转构造可能越来越重要。 该项目将巩固对布兰斯菲尔德海峡的地球物理分析，并通过考虑海峡与邻近的南设得兰群岛和“前牙”的关系来建立在它的基础上。 EW91-01 MCS数据非常适合分析“背弧”中看到的结构是否与沟槽和“前弧”的结构和过程有关。 该分析的一个关键部分是测试以下假设：沟槽后背部正在引起布兰斯菲尔德海峡的“背面”扩展。 来自意大利和英国的高质量MCS数据将与EW91-01 MCS数据集成，以更全面的面积覆盖范围和对“背面arc”和```fore fore-arc''中结构风格的地震分析。EW91-01潜在的现场数据还将在研究中与其他区域相比。 (e.g., Lau Basin, Gulf of California) should allow an estimate of the relative importance of processes of marginal basin formation and evolution on global versus local scales. Furthermore, the common history that the Antarctic Peninsula Pacific margin shares with the South American Pacific margin as parts of the convergent plate margin of Gondwanaland means that Bransfield Strait can be considered a modern analog for Early to智利南部的Rocas Verdes边缘盆地的白垩纪进化对于理解安第斯造成的早期阶段至关重要。