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: 2019
• 资助国家: 加拿大
• 起止时间: 2019-01-01 至 2020-12-31
• 项目状态: 已结题
• 来源: https://www.nserc-crsng.gc.ca/ase-oro/Details-Detailles_eng.asp?id=686574
• 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(CMBS)以快速隆升和伴随的下沉、陡峭和短的河流集水区和较高的沉积速率为特征。因此，CMBS的沉积速率明显高于克拉通内前陆盆地和被动边缘，这体现在独特的地层结构和旋回沉积模式的保存上。这项拟议的研究旨在描述CMBS中的浅海地层，以了解这些系统如何随着时间的推移而演变，包括解决气候和地震周期性问题。研究将侧重于两个CMBS，涉及制定盆地的异地地层学框架和确定盆地内的周期性沉积模式。*大多数拟议的研究集中在加拿大温哥华岛格鲁吉亚盆地的下纳奈莫群。格鲁吉亚盆地是一个弧前盆地，下纳奈莫群局部厚度超过1公里。沿河流连续露出的露头将以高分辨率记录，并将使用相分析来识别地层重要的表面。然后将使用表面沿沉积走向和跨沉积走向细分地层，并将获取碎屑锆石数据来测试和完善异地层学对比。解决纳奈莫群下部的沉积旋回性将利用相分析，并识别地震岩(地震旋回性)和沉积的横向和垂直变化(气候旋回性)。被认为指示构造作用和气候的旋回将得到包括d13C和C：N比在内的地球化学指标的证实。*台湾西部前陆盆地是一个快速隆起的CMB，在台湾西部密集的露头中暴露出厚厚的年轻地层序列(&lt；6 Ma)。露头的年龄在生物地层学上是确定的，因此有可能在时间等值的沉积中评估沿线走向和下倾相关系，并研究地震和气候旋回的产物。研究将集中在上新世晚期奎丘林组和早更新世朱兰组。将详细记录露头，并将使用地球化学数据(d13C、d18O和C：N比)来解决和改进气候和地震周期。基于无人机的3D摄影测量将用于重建露头并量化岩层厚度和地层结构。*这项工作的影响是多方面的。在格鲁吉亚盆地，我们将为下纳奈莫群建立一个盆地范围的地层格架，评估旋回沉积，并解决沉积中心和沉降/构造作用的变化。与台湾的研究相结合，这项工作的结果将产生全球影响，因为我们将开发工具和模型来识别和解决浅海地层中的气候和地震旋回，并制定将它们与相对海平面变化引起的旋回区分的标准。