通过质量平衡透镜观察耦合河道-洪泛平原动力学和由此产生的地层结构

IF 2 4区 地球科学 Q1 GEOLOGY
Kyle M. Straub, Ripul Dutt, Robert A. Duller
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引用次数: 0

摘要

全盆地调节作用的产生和伴生的沉积物体沉积对地层结构起着根本的控制作用,但这种关系的细节尚未完全了解。这是因为尚不清楚调节作用的产生如何直接影响河道过程(即河道迁移、河道崩裂)和洪泛平原过程的形态动力学,而这两者本身是动态耦合的,对地层结构的性质至关重要。为了解决这个问题,我们扩展了现有的理论,将沉积物质量平衡和由此产生的地层结构联系起来。我们使用了两个扇三角洲实验,每个实验都经历了不同的调节速率,以测量关键的地表形态计量学和地下沉积特征。重要的是,在这些实验中,泥沙以层载和悬浮物的方式运移,形成了以河道体为特征的地层,周围是由悬浮物沉积的岸上地层。从这些数据中,我们使用三个关键时间尺度来捕捉系统在放置到质量平衡空间时的整体行为:撕脱建立时间尺度(TA)和通道迁移时间尺度(TV),它们定义了短期的表面自生,以及包含长期沉积的吸积时间尺度(TC)。我们发现,在质量平衡空间中,TC/TA和TC/TV的比值与容纳速率无关,这支持了通道动态对环境边界条件的自组织响应。关键沉积环境中生成的地层在很大程度上支持这一行为,特别是河床砂体的沉积。因此,我们的研究结果表明,在质量平衡空间中,通道体密度与调节速率无关。我们发现,尽管远场岸上沉积对盆地地层有很大的贡献,但远场岸上沉积速率对调节作用不敏感,实验之间自生时间尺度的差异很大程度上是由河道沉积速率的差异造成的,这突出了河道动力学与调节作用之间的密切耦合。更一般地说,在质量平衡空间中观察到的地表形态动力学对调节生产的自组织响应提供了一个基于过程的框架,来解释平衡质量在预测下系统沉积物粒度分异和沉积结构方面的效用。
本文章由计算机程序翻译,如有差异,请以英文原文为准。
Coupled channel–floodplain dynamics and resulting stratigraphic architecture viewed through a mass-balance lens
ABSTRACT Basin-wide accommodation production and associated sediment mass deposition exert fundamental controls on stratigraphic architecture, but the details of this relationship are not fully understood. This is because it is unknown how accommodation production directly influences morphodynamics both in terms of channel process (i.e., channel migration, channel avulsion) and floodplain process, both of which are themselves coupled dynamically and are critical to the nature of stratigraphic architecture. To address this, we expand on existing theory that links sediment mass balance and resultant stratigraphic architecture. We use two fan-delta experiments that each experience different rates of accommodation production to measure key surface morphometrics and subsurface sedimentary characteristics. Importantly, sediment was transported in bedload and suspension in these experiments, resulting in construction of strata characterized by channel bodies surrounded by overbank strata deposited from suspension fallout. From these data we use three key timescales to capture the overall behavior of the system when placed into mass-balance space: avulsion setup timescales (TA) and channel mobility timescales (TV) that define short-term surface autogenics, and an accretion timescale (TC) that incorporates longer-term deposition. We find that the ratio of both TC/TA and TC/TV are independent of accommodation production rate in mass-balance space, which supports a self-organized response of channel dynamics to environmental boundary conditions. The fraction of strata generated from key depositional environments largely supports this behavior, particularly for channel sand bodies that resulted in deposition from bedload transport. As such, our results suggest that channel-body density is independent of accommodation production rate in a mass-balance space. We found that, although contributing to a significant fraction of the basin strata, far-field overbank deposition rates are insensitive to accommodation production and that differences in autogenic timescales between experiments largely resulted from differences in channel deposition rates, highlighting the close coupling between channel dynamics and accommodation generation. More generally the observed self-organized response of surface morphodynamics to accommodation production in mass-balance space provides a process-based framework to explain the utility of balancing mass for the prediction of down-system sediment size fractionation and sedimentary architecture.
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来源期刊
CiteScore
3.80
自引率
5.00%
发文量
50
审稿时长
3 months
期刊介绍: The journal is broad and international in scope and welcomes contributions that further the fundamental understanding of sedimentary processes, the origin of sedimentary deposits, the workings of sedimentary systems, and the records of earth history contained within sedimentary rocks.
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