Deformed sedimentary basins as records of orogenesis

作为造山作用记录的变形沉积盆地

• 批准号: RGPIN-2020-04171
• 负责人: Waldron, John
• 金额: $ 2.62万
• 依托单位: University of Alberta
• 依托单位国家: 加拿大
• 项目类别: Discovery Grants Program - Individual
• 财政年份: 2020
• 资助国家: 加拿大
• 起止时间: 2020-01-01 至 2021-12-31
• 项目状态: 已结题
• 来源: https://www.nserc-crsng.gc.ca/ase-oro/Details-Detailles_eng.asp?id=716823
• 关键词: Deformed; sedimentary; basins; records; orogenesis

Orogens (mountain belts) are major features of the Earth, known be formed when buoyant continental lithosphere interacts with convergent plate boundaries. However, explaining their diversity in terms of plate scenarios is a major challenge. The Appalachian-Caledonide orogen formed during Pangea amalgamation. It has an unparalleled stratigraphic, geochronologic, and geophysical database. Previous work has tended to assume that it formed by orthogonal plate convergence, and that stratigraphic units and structures were laterally continuous. Nonetheless, modern plate tectonics tells us that convergence is typically oblique, and that colliding terranes have irregular shapes. The objective of the proposed research will be to explain the substantial along-strike variations in this typical ancient orogen in terms of contrasts and lateral discontinuities in obliquely converging plates. The proposed program will train highly qualified personnel from undergraduate to doctoral level, using field mapping, interpretation of remotely sensed and seismic reflection data, detrital zircon provenance, analogue deformation modelling, and tectonic restoration. Our previous work showed that salt tectonics is under-recognized in the late Paleozoic record of the northern Appalachians; salt movement was triggered by underlying strike-slip faults. A basin-wide tectonic model will allow us to restore the late Paleozoic motion, as a prerequisite to understanding earlier tectonics, and will lead to better understanding of how strike-slip faults interact with salt deposits elsewhere. The earlier history of the orogen involved Ordovician to Devonian accretion of multiple Gondwana-derived terranes to the margin of Laurentia. These accretion events include the Salinic, Acadian and Neo-Acadian orogenies, and led to major, but localized, crustal thickening. We will use detrital zircon U/Pb and Lu/Hf analyses from sandstone deposited during this interval to distinguish between tectonic models for these events. Much of the earliest (Taconic) deformation took place on the Laurentian margin, and is interpreted to record continent-arc collision. However, Laurentian units also high in the Caledonide thrust stack in Baltica have been interpreted as derived from Greenland, but their stratigraphic record has no equivalents there; transport along the orogen must have occurred. We will trace the history and movement of components of the Laurentian margin within the orogen, using modern margins as analogues (e.g. the N Australian margin), and attempt to explain how subduction was initiated following breakup of the earlier supercontinent Rodinia. The proposed research will lead to an actualistic model for the development of the Appalachian Caledonide system incorporating new data and older neglected data sets to fully account for lateral variations in terrane geometry and motion. It will impact the plate-tectonic causes of orogenesis and the search for resources in orogens generally.

造山带（山脉）是地球的主要特征，已知是在浮力大陆岩石圈与会聚板块边界相互作用时形成的。然而，从板块场景的角度解释它们的多样性是一个重大挑战。 阿巴拉契亚-喀里多尼德造山带是在盘古大陆合并期间形成的。它拥有无与伦比的地层学、地质年代学和地球物理数据库。以前的工作倾向于假设它是由正交板块聚合形成的，并且地层单元和结构是横向连续的。尽管如此，现代板块构造学告诉我们，汇聚通常是倾斜的，并且碰撞的地体具有不规则的形状。拟议研究的目的是通过倾斜会聚板块的对比和横向不连续性来解释这个典型的古代造山带的显着的沿走向变化。 拟议的项目将利用野外测绘、遥感和地震反射数据解释、碎屑锆石物源、模拟变形建模和构造恢复，培养从本科到博士水平的高素质人才。 我们之前的工作表明，在阿巴拉契亚山脉北部的晚古生代记录中，盐构造尚未得到充分认识。盐运动是由底层走滑断层引发的。全盆地的构造模型将使我们能够恢复晚古生代的运动，作为了解早期构造的先决条件，并将有助于更好地了解走滑断层如何与其他地方的盐矿床相互作用。 造山带的早期历史涉及奥陶纪至泥盆纪多个冈瓦纳大陆衍生地体向劳伦大陆边缘的增生。这些吸积事件包括盐化造山运动、阿卡迪亚造山运动和新阿卡迪亚造山运动，并导致主要但局部的地壳增厚。我们将使用该区间沉积的砂岩中的碎屑锆石 U/Pb 和 Lu/Hf 分析来区分这些事件的构造模型。 大部分最早的（塔科尼）变形发生在劳伦边缘，并被解释为记录了大陆弧碰撞。然而，波罗的海喀里多尼德逆冲层中的劳伦森单位也被解释为源自格陵兰岛，但它们的地层记录在那里没有对应物；沿着造山带的运输必定发生过。我们将使用现代边缘（例如澳大利亚北部边缘）作为类比，追踪造山带内劳伦特边缘组成部分的历史和运动，并尝试解释早期超大陆罗迪尼亚分裂后如何引发俯冲作用。 拟议的研究将为阿巴拉契亚喀里多尼德系统的发展建立一个现实模型，该模型结合了新数据和较旧的被忽视的数据集，以充分考虑地体几何形状和运动的横向变化。它将影响造山运动的板块构造原因和造山带资源的总体寻找。