Collaborative Research: A Multidisciplinary Study of an Exhumed Active Continental Margin: The Wrangell Transect, SE Alaska

合作研究：对挖出的活动大陆边缘的多学科研究：阿拉斯加东南部的兰格尔断面

• 批准号: 0207586
• 负责人: Maria Crawford
• 金额: $ 7.31万
• 依托单位: Bryn Mawr College
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2002
• 资助国家: 美国
• 起止时间: 2002-06-01 至 2006-05-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=0207586&HistoricalAwards=false
• 关键词: Collaborative; Research; Multidisciplinary; Study; Exhumed

The PI's propose a multidisciplinary study of Cretaceous and Tertiary rocks along an east-west transect in the Wrangell - Petersburg - Prince of Wales Island area of SE Alaska (= Wrangell transect). Previous research demonstrates that integration of paleomagnetic studies with geochronologic, thennochronologic, barometric, and structural geologic observations can produce important insights into the tectonic evolution of the Insular superterrane and Coast Mountains orogen in western BC and SE Alaska. The PI's recent results from near Prince Rupert show that paleomagnetism is a key component of multidisciplinary efforts investigating exhumed shallow and mid-crustal sections. When accompanied by geologic observations resulting from a carefully coordinated multidisciplinary research program, paleomagnetic data on intrusive igneous rocks yield critical infon-nation on the tectonic development of defon-ned regions that cannot otherwise be obtained. For example, the PI's have documented that panels of crust containing the Palcocene Quottoon igneous complex east of the Coast shear zone have experienced east-side-up tilts ranging to 40' during Eocene extension. In addition, their geochronologic, paleomagnetic, barometric, and structural geologic data suggest that the midCretaceous Ecstall pluton was folded during west-directed thrusting. These discoveries are fundamental to understanding the crustal architecture and tectonic development of the continental margin in the northern Cordillera.Because igneous rocks were emplaced into this part of the magmatic arc during the Cretaceous, throughout the Paleogene, and into the Miocene, the Wrangell transect provides the opportunity to track deformation of an evolving convergent to strike-slip plate margin in space and time. Methods will include U/Pb geochronology of zircon and sphene, Al-in-homblende barometry, 40 Ar/39 Ar thennochronology, (U-Th)/He dating of zircon, metamorphic petrology, and structural geologic investigations in addition to paleomagnetic analysis. Preliminary investigations on the eastern portion of the transect indicate that this area experienced - 1 7' ESEside-up tilt about an axis with azimuth 22' since 20 Ma. Observations from across the transect indicate that paleomagnetic directions from Cretaceous plutons are variable, with both concordant and discordant inclinations. Paleomagnetic study of the Cretaceous and Tertiary igneous rocks of the Wrangell transect, coupled with the geochronologic, thermochronologic, and barometric analyses, can determine: (1) when and where Cenozoic deformation occurred; and (2) whether regionally consistent tilting/folding and/or large-scale transport can account for discordant paleomagnetic directions from Cretaceous plutons. Combined with results from the Prince Rupert area, successful completion of the proposed research can provide a comprehensive model for the tectonic and paleogeographic evolution of the Coast Mountains and Insular superterrane for the past I 00 m.y.

PI提出了一项对wrangell -Petersburg-彼得斯堡 - 威尔士岛苏阿拉斯加王子区的西方样带的白垩纪和三级岩石的多学科研究（= Wrangell tr​​ractect）。 先前的研究表明，将古磁研究与年代学，非人工学，气压和结构地质观察的整合可以产生重要的见解，以对卑诗省和SE Alaska西部的岛上超级型和沿海造型的构造演化产生构造的见解。 PI最近来自鲁珀特亲王的最新结果表明，古磁主义是调查挖掘浅层和中期截面的多学科努力的关键组成部分。 当伴随着精心协调的多学科研究计划引起的地质观察时，有关侵入性火成岩的古磁数据产生了关键的基础知识，这些基础是无法获得辩护区的构造发展的关键基础，而这些岩石的发展是无法获得的。 例如，PI已记录到，在始新世延伸期间，沿海剪切带以东的壁式近代火成岩综合体的外侧倾斜到40'。 此外，它们的测量，古磁，气压和结构地质数据表明，在向西推动的推力过程中，零星中间的狂热岩石被折叠。 这些发现是理解北部山脉大陆边缘的地壳建筑和构造建筑的基础。在时空和时间上跟踪不断发展的融合到滑滑板边缘的变形的机会。 方法将包括锆石和Sphene的U/PB年代学，Al-In-blende气压，40 AR/39 AR THENNOCOROGY，（U-TH）/HE锆石的日期，变质岩石学和结构地质研究，除了古磁分析外。 对横断面东部部分的初步研究表明，自20 mA以来，该区域经历了该区域的经历-1 7'Eseside -up倾斜，围绕具有22'的方位角22'的轴。 从横断面的观察结果表明，来自白垩纪岩石的古磁方向是可变的，均具有一致性和不一致的倾向。 Wrangell样带的白垩纪和第三纪火成岩的古磁研究与测量学，热体学和气压分析相结合，可以确定：（1）在何时何地发生在何时何地发生在何时何地发生； （2）区域一致的倾斜/折叠和/或大规模运输是否可以解释白垩纪岩石的不一致的古磁方向。 结合鲁珀特亲王地区的结果，成功完成拟议的研究可以为过去的M.Y. 00 00 M.y提供了一个全面的模型。