Depositional Cyclicity and Evolution of Convergent-Margin Basins

汇聚边缘盆地的沉积旋回性和演化

• 批准号: RGPIN-2019-04528
• 负责人: Dashtgard, Shahin
• 金额: $ 2.62万
• 依托单位: Simon Fraser University
• 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=751130
• 关键词: Depositional; Cyclicity; Evolution; Convergent; Margin

Convergent-margin basins (CMBs) are typified by rapid uplift and associated subsidence, steep and short river catchments, and elevated sedimentation rates. As a consequence, sediment accumulation rates are significantly greater in CMBs than in intracratonic foreland basins and passive margins, and this is manifested in distinctive stratal architectures and preservation of cyclical sedimentation patterns. The proposed research aims to characterize shallow-marine strata in CMBs to understand how these systems evolve through time, including resolving both climate and earthquake cyclicity. Research will focus on two CMBs and involves developing an allostratigraphic framework for the basins and identifying cyclical sedimentation patterns across the basins. Most of the proposed research focuses on the lower Nanaimo Group in the Georgia Basin, Vancouver Island, Canada. The Georgia Basin is a forearc basin (CMB) and the lower Nanaimo Group locally exceeds 1 km in thickness. Continuous outcrops exposed along rivers will be logged at high resolution and facies analysis will be employed to identify stratigraphically important surfaces. Surfaces will then be used to subdivide strata along and across depositional strike, and detrital zircon data will be acquired to test and refine allostratigraphic correlations. Resolving depositional cyclicity in the lower Nanaimo Group will utilize facies analysis, and recognition of both seismites (earthquake cyclicity) and lateral and vertical changes in sedimentation (climate cyclicity). Cycles considered indicative of tectonism and climate will be corroborated with geochemical proxies, including d13C and C:N ratios. The Western Foreland Basin, Taiwan is a rapidly uplifting CMB and thick sequences of young strata (< 6 Ma) are exposed in closely spaced outcrops in western Taiwan. The ages of outcrops are well established biostratigraphically, and hence it is possible to assess alongstrike and down-dip facies relations in time-equivalent deposits and to study the products of earthquakes and climate cycles. Research will focus on the late Pliocene Kuechulin Formation and early Pleistocene Cholan Formation. Outcrops will be logged in detail and geochemical data (d13C, d18O and C:N ratios) will be used to resolve and refine climate and earthquake cycles. Drone-based 3D photogrammetry will be used to reconstruct outcrops and quantify both bed thicknesses and stratal architectures. The impacts of this work are multiple. In the Georgia Basin, we will produce a basin-wide allostratigraphic framework for the lower Nanaimo Group, assess cyclic deposition and resolve changes in depocenters and subsidence/tectonism. When combined with research in Taiwan, the results of this work will have a global impact in that we will develop tools and models for recognizing and resolving climate and earthquake cycles in shallow-marine strata, and criteria for distinguishing them from cycles induced by changes in relative sea level.

会聚边缘盆地的典型特征是迅速的隆升和伴随的沉降、陡短的河流集水区和较高的沉积速率。因此，cmb的沉积速率明显大于克拉通内前陆盆地和被动边缘，这表现在独特的地层结构和循环沉积模式的保存上。提出的研究旨在表征CMBs中的浅海地层，以了解这些系统如何随时间演变，包括解决气候和地震周期。研究将集中在两个CMBs上，并涉及为盆地开发一个不同的地层格架，并确定整个盆地的旋回沉积模式。大多数拟议的研究集中在加拿大温哥华岛乔治亚盆地的纳奈莫组下部。乔治亚盆地为弧前盆地，下部纳奈莫群局部厚度超过1 km。沿河暴露的连续露头将进行高分辨率测井，相分析将用于识别地层学上重要的表面。然后，表面将用于沿沉积走向和跨沉积走向细分地层，并获得碎屑锆石数据，以测试和细化异位地层对比。确定纳奈莫群下部沉积旋回性将利用相分析、震积岩（地震旋回性）和沉积的横向和纵向变化（气候旋回性）的识别。旋回被认为是构造运动和气候的指示，将用地球化学代用物（包括d13C和C:N比）加以证实。台湾西部前陆盆地是一个快速隆升的CMB，在台湾西部密集的露头中暴露出厚层序（< 6 Ma）的年轻地层。露头的年龄在生物地层学上已经很好地确定了，因此有可能评估时间等效矿床的顺走向和下倾相关系，并研究地震和气候旋回的产物。研究重点为上新世晚期的奎楚林组和早更新世的赤兰组。露头将被详细记录，地球化学数据（d13C、d18O和C:N比值）将被用来解析和细化气候和地震周期。基于无人机的3D摄影测量将用于重建露头并量化床层厚度和地层结构。这项工作的影响是多方面的。在乔治亚盆地，我们将为下纳奈莫群（Nanaimo Group）建立一个全盆地范围的异地层格架，评估旋回沉积，并解决沉积中心和沉降/构造作用的变化。结合台湾的研究，本工作的结果将具有全球影响，因为我们将开发识别和解决浅海地层气候和地震周期的工具和模型，以及区分它们与相对海平面变化引起的周期的标准。