Collaborative Research/RUI: The Role of Orogen Parallel Fault Systems in the Late Exhumation History of a Convergent Orogen

合作研究/RUI：造山带平行断层系统在聚合造山带晚期折返历史中的作用

• 批准号: 0308938
• 负责人: Mary Roden-Tice
• 金额: --
• 依托单位: SUNY College at Plattsburgh
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2003
• 资助国家: 美国
• 起止时间: 2003-06-01 至 2006-05-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=0308938&HistoricalAwards=false
• 关键词: Collaborative; Research; RUI; Role; Orogen

AbstractPatterns of previously published 40 Ar/ 39 Ar mineral ages and new apatite fission track ages determined by the PIs show distinct time-temperature discontinuities across two major orogen-parallel fault systems in the northern Appalachians. These discontinuities, across a portion of the Norumbega fault system in Maine and the Ammonoosuc fault along the Vermont-New Hampshire border, strongly suggest that portions of these fault systems accommodated significant (perhaps up to 2-3 km) vertical movement in Late Cretaceous or younger time. Both of these fault systems flank the highest grade portions of the Acadian orogen and in both instances the patterns of cooling ages suggest that rocks in the core of the orogen moved up relative to down-dropped rocks on the flanks of the orogen. This proposal outlines a collaborative low-temperature thermochronological study (apatite fission-track and (U-Th)/He) across these two fault systems with the goals of: oDetermining the regional extent of the low-temperature thermochronological discontinuities along these orogen-parallel fault systems. Across strike sampling traverses will allow the PI's to test a working hypothesis that proposes these previously established orogen-parallel zones of weakness accommodated significant differential post-orogenic isostatic uplift across the orogen.oDetermining if the low-temperature discontinuities are confined to the margins of the orogen or whether other structures within the core of the orogen may also be accommodating post-orogenic displacements.oDetermining how long these structures have been active. Preliminary apatite fission track dating traverses across both the Norumbega and Ammonoosuc fault systems have yet to establish a time of contemporaneous cooling across the structures. Results to date suggest portions of both these structures have been active into the Late Cretaceous, but no lower age limit has been established. The PI's propose to incorporate the lower closure temperature (U-Th)/He technique (~ 60-70 o C closure temperature) into their study which will provide information on the timing of cooling at later times and reveal whether the rocks currently juxtaposed across these faults cooled contemporaneously during the Late Cretaceous/Early Tertiary.oEstimating the magnitude of post-orogenic displacement along these orogen-parallel fault systems and determining how important they were in the exhumation history of the orogen.The results of this study will not only provide much needed information on the exhumation history of the northern Appalachians, but will have a broader impact on the understanding of mechanisms and processes associated with post-orogenic mountain belt exhumation. Orogen-parallel zones of weakness are associated with nearly all orogenic belts and what role these structures play in the late exhumation history of mountain belts is unclear. The proposed low-temperature thermochronological study of two orogen flanking fault zones will provide much needed information on the role of these structures in post-orogenic exhumation. This proposed research will involve collaboration between two PI's with experience in low-temperature thermochronology, regional tectonics, and studies of northern Appalachian fault systems. Importantly, undergraduate students from both institutions will be fully integrated into the project and will be involved in sampling, sample processing, data analysis and interpretation.

摘要：先前发表的 40 Ar/ 39 Ar 矿物年龄和由 PI 确定的新磷灰石裂变径迹年龄的模式显示，阿巴拉契亚山脉北部两个主要造山带平行断层系统存在明显的时间-温度不连续性。这些不连续性横跨缅因州诺伦贝加断层系统的一部分和佛蒙特州-新罕布什尔州边界的阿蒙诺苏克断层，强烈表明这些断层系统的部分在白垩纪晚期或年轻的时候。这两个断层系统都位于阿卡迪亚造山带最高等级部分的侧面，在这两种情况下，冷却年龄的模式表明，造山带核心的岩石相对于造山带侧面的下落岩石向上移动。该提案概述了这两个断层系统的协作低温热年代学研究（磷灰石裂变径迹和（U-Th）/He），其目标是： o确定沿着这些造山带平行的低温热年代学不连续性的区域范围故障系统。跨走向采样横贯将使 PI 能够测试一个工作假设，该假设提出这些先前建立的与造山带平行的薄弱区适应了整个造山带上显着差异的造山后均衡抬升。 o确定低温不连续性是否仅限于造山带的边缘造山带或造山带核心内的其他结构是否也可以容纳造山后位移。o确定这些结构已经活跃了多长时间。穿过Norumbega 和Ammonoosuc 断层系统的初步磷灰石裂变径迹测年尚未确定跨结构的同时冷却时间。迄今为止的结果表明，这两个结构的一部分一直活跃到白垩纪晚期，但尚未确定年龄下限。 PI 建议将较低的闭合温度 (U-Th)/He 技术（~ 60-70 o C 闭合温度）纳入他们的研究中，这将提供有关稍后冷却时间的信息，并揭示当前岩石是否并置这些断层在白垩纪晚期/第三纪早期同时冷却。o估计沿着这些造山带平行断层系统的造山后位移幅度，并确定它们在折返历史中的重要性这项研究的结果不仅将提供有关北阿巴拉契亚山脉折返历史的急需信息，还将对理解与后造山带折返相关的机制和过程产生更广泛的影响。造山带平行薄弱带几乎与所有造山带有关，这些结构在造山带晚期折返历史中发挥的作用尚不清楚。拟议对两个造山带侧翼断层带进行低温热年代学研究将为了解这些结构在造山后折返中的作用提供急需的信息。这项拟议的研究将涉及两位在低温热年代学、区域构造学和阿巴拉契亚北部断层系统研究方面拥有丰富经验的 PI 之间的合作。重要的是，两个机构的本科生将完全融入该项目，并参与采样、样本处理、数据分析和解释。