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.

该奖项由 2009 年美国复苏和再投资法案（公法 111-5）资助。该研究小组将首次详细说明沉积盆地对大洋扩张脊俯冲的响应，这是一种常见的构造过程，从根本上讲，重塑和重组会聚的大陆边缘。 弧前盆地是沿汇聚边缘最常见的盆地之一，是大型沉积物储藏库，有可能保存扩张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地区，可以研究弧前盆地展脊俯冲的长期沉积记录。拟议的研究对美国公民也有直接影响。 要研究的古新世？始新世地层对于煤炭和甲烷储量具有重要的经济意义。 了解洋脊俯冲对于库克湾弧前盆地的碳氢化合物勘探也很重要。 此外，该研究的一个主要目标是更好地描述城堡山断层系统的特征，该断层系统沿线的活动对居住在安克雷奇-帕尔默-瓦西拉地区的 300,000 人构成严重危害。 这项科学推广计划包括与来自阿拉斯加乡村社区的 K-12 美洲原住民学生以及阿拉斯加大学的本科生进行为期两天的实地考察，他们将在那里了解地球上暴露得最好的收敛边缘之一。 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。美洲原住民学生是围绕地质问题（金矿和煤炭开采、石油勘探、地震等）长大的，但许多人可能没有将这些问题与沿聚合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沉积盆地对扩张脊俯冲的响应提供了绝佳的机会。在马塔努斯卡山谷地区，北部白垩纪-古新世弧形岩体和南部白垩纪增生棱柱地层之间，出露地层厚度超过 2800 m。拟议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物堆积的主要阶段与阿拉斯加南部的扩张脊俯冲和板窗岩浆作用同步； (2) 扩张脊俯冲改变了盆地的沉积和构造形态，导致原来的海相弧前盆地在地面上隆起，随后迅速沉降和陆相沉积； (3)扩张的山脊俯冲引发了弧岩体和变质岩的折返，这一过程记录在弧前盆地地层的碎屑成分中。拟议研究中的一种新方法是，弧前盆地地层不仅将用于确定洋脊俯冲期间弧前盆地发生的岩浆和沉积过程的类型，而且还可作为了解相关过程时间的桥梁穿过增生棱柱和会聚边缘的岩浆弧部分。