Collaborative Research: Sedimentary Basin Response to Paleocene-Eocene Spreading Ridge Subduction in South-Central Alaska

合作研究：沉积盆地对阿拉斯加中南部古新世-始新世扩张脊俯冲的响应

• 批准号: 0910945
• 负责人: Kenneth Ridgway
• 金额: $ 13万
• 依托单位: Purdue University
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2009
• 资助国家: 美国
• 起止时间: 2009-08-15 至 2012-07-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=0910945&HistoricalAwards=false
• 关键词: Collaborative; Research; Sedimentary; Basin; Response

This award is funded under the American Recovery and Reinvestment Act of 2009 (Public Law 111-5).This research group will give one of the first detailed accounts of the sedimentary basin response to oceanic spreading-ridge subduction, a common tectonic process that fundamentally reshapes and reorganizes convergent continental margins. Forearc basins, one of the most common along convergent margins, are large sediment repositories that have the potential to preserve a detailed record of spreading-ridge subduction processes. Preliminary work indicates that the Matanuska Valley region of southern Alaska is a fertile area, perhaps the best on Earth, to examine the long term sedimentary record of spreading-ridge subduction in a forearc basin. The proposed research also has direct implications for US citizens. The Paleocene?Eocene strata to be studied are economically important for coal and methane reserves. Understanding ridge subduction will also be important for hydrocarbon exploration in the forearc basin in the Cook Inlet. In addition, a major objective of the research is better characterization of the Castle Mountain fault system, activity along which presents a serious hazard for 300,000 people that live in the Anchorage-Palmer-Wasilla region. The scientific outreach plan involves a two-day field trip with K?12 Native American students from rural Alaskan communities, as well as undergraduate students from the University of Alaska, where they will learn about one of the best exposed convergent margins on Earth. The PIs will help students understand the impact of tectonic processes that shape their local environment and communities. The Native American students have grown up around geological issues (gold and coal mining, petroleum exploration, earthquakes, etc.), but many probably have not made connections between these issues and tectonic processes along convergent margins.Forearc basin strata in south-central Alaska provide a superb opportunity to study sedimentary basin response to spreading ridge subduction. Well-exposed strata over 2800 m thick crop out in the Matanuska Valley region between Cretaceous-Paleocene arc plutons to the north and Cretaceous accretionary prism strata to the south. The proposed interdisciplinary study will evaluate three hypotheses: (1) That the main phase of Paleocene-Eocene basin development and sediment accumulation was synchronous with spreading ridge subduction and slab window magmatism in southern Alaska; (2) That spreading ridge subduction modified the depositional and structural configuration of the basin, resulting in subaerial uplift of the formerly marine forearc basin followed by rapid subsidence and nonmarine deposition; and (3) That spreading ridge subduction triggered exhumation of arc plutons and metamorphic rocks, and that this process is recorded in the detrital composition of the forearc basin strata. A new approach in the proposed research is that strata of the forearc basin will be used to not only determine the types of magmatic and sedimentary processes that occur in forearc basins during ridge subduction but also to serve as a bridge for understanding the timing of related processes across both the accretionary prism and the magmatic arc parts of convergent margins.

该奖项是根据2009年美国复苏和再投资法案（公法111-5）资助的。这个研究小组将首次详细描述沉积盆地对海洋伸展脊俯冲的反应，这是一种从根本上重塑和重组聚合大陆边缘的常见构造过程。弧前盆地是沿辐合边缘最常见的盆地之一，是大型沉积物储存库，有可能保存扩展脊俯冲过程的详细记录。初步工作表明，阿拉斯加南部的马塔努斯卡山谷地区是一个肥沃的地区，也许是地球上最好的，可以用来研究弧前盆地中伸展脊俯冲的长期沉积记录。这项拟议中的研究对美国公民也有直接影响。古新世?研究的始新世地层对煤和甲烷储量具有重要的经济意义。了解洋脊俯冲作用对库克湾弧前盆地油气勘探也具有重要意义。此外，研究的一个主要目的是更好地描述城堡山断层系统，该断层系统的活动对生活在安克雷奇-帕尔默-瓦西拉地区的30万人构成严重威胁。科学拓展计划包括与K？来自阿拉斯加农村社区的12名美国原住民学生，以及来自阿拉斯加大学的本科生，他们将在那里了解地球上最暴露的收敛边缘之一。pi将帮助学生了解塑造当地环境和社区的构造过程的影响。美国土著学生是在地质问题（金矿和煤矿开采、石油勘探、地震等）的环境中长大的，但许多人可能没有把这些问题与沿汇聚边缘的构造过程联系起来。阿拉斯加中南部的弧前盆地地层为研究伸展脊俯冲作用下的沉积盆地提供了极好的机会。在马塔努斯卡山谷地区，北至白垩纪-古新世弧深岩体，南至白垩纪增生棱柱地层之间，发育厚度超过2800 m的裸露地层。提出的跨学科研究将评估三个假设：(1)古新世-始新世盆地发育和沉积的主要阶段与阿拉斯加南部伸展脊俯冲和板块窗岩浆作用同步；(2)伸展脊俯冲改变了盆地的沉积和构造形态，导致原海相弧前盆地陆下隆升，随后迅速沉降并发生非海相沉积；(3)伸展脊俯冲作用引发了弧深岩体和变质岩的掘出，这一过程记录在弧前盆地地层的碎屑组成中。提出了一种新的研究方法，即利用弧前盆地地层不仅可以确定在海脊俯冲过程中发生在弧前盆地的岩浆和沉积过程的类型，而且可以作为了解增生棱柱和会聚边缘岩浆弧部分相关过程的时间的桥梁。