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: 2022
• 资助国家: 加拿大
• 起止时间: 2022-01-01 至 2023-12-31
• 项目状态: 已结题
• 来源: https://www.nserc-crsng.gc.ca/ase-oro/Details-Detailles_eng.asp?id=750914
• 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，解释板块情景方面的多样性是一个重大挑战。阿巴拉契亚-加里东造山带形成于泛大陆融合作用期间。它拥有无与伦比的地层、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会聚形成的，地层单位和构造是横向连续的。尽管如此，现代板块构造学告诉我们，会聚通常是倾斜的，碰撞的板块具有不规则的形状。拟议的研究的目的将是解释实质性的沿走向变化，在这个典型的古老造山带的对比度和横向不连续性在斜向收敛板块。拟议的方案将利用实地测绘、遥感和地震反射数据解释、碎屑锆石来源、模拟变形建模和构造恢复，培训从本科到博士的高素质人才。我们以前的工作表明，盐构造是认识不足的晚古生代记录的北方阿巴拉契亚山脉;盐运动是由下面的走滑断层触发。一个盆地范围的构造模型将使我们能够恢复晚古生代的运动，作为理解早期构造的先决条件，并将导致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到泥盆纪的多个冈瓦纳衍生的碎屑物到劳伦大陆边缘的增生。这些加积事件包括Salinic，Escherichian和Neo-Escherichian造山作用，并导致了主要的，但局部的地壳增厚。我们将使用碎屑锆石U/Pb和Lu/Hf分析砂岩沉积在这段时间来区分这些事件的构造模型。最早期的塔康尼克（Taconic）变形发生在劳伦阶边缘，被解释为记录了大陆弧碰撞。然而，同样位于波罗的海加里东逆冲叠层高处的劳伦单位被解释为源自格陵兰，但它们的地层记录在那里没有对应的记录;一定发生了沿沿着造山带的迁移。我们将追溯历史和运动的组成部分的造山带内的劳伦森边缘，使用现代的边缘类似物（如澳大利亚北部的边缘），并试图解释俯冲是如何开始后，较早的超大陆Rodinia的分裂。拟议的研究将导致一个现实主义的模型，阿巴拉契亚Caledonide系统的发展，结合新的数据和旧的被忽视的数据集，以充分考虑到横向变化的几何形状和运动。它将从总体上影响造山作用的板块构造成因和造山带内资源的寻找。