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Evaluating alluvial stratigraphic response to cyclic and non‐cyclic upstream forcing through process‐based alluvial architecture modelling
Basin Research ( IF 2.8 ) Pub Date : 2020-04-11 , DOI: 10.1111/bre.12454 Youwei Wang 1 , Joep E. A. Storms 1 , Allard W. Martinius 1, 2 , Derek Karssenberg 3 , Hemmo A. Abels 1
Basin Research ( IF 2.8 ) Pub Date : 2020-04-11 , DOI: 10.1111/bre.12454 Youwei Wang 1 , Joep E. A. Storms 1 , Allard W. Martinius 1, 2 , Derek Karssenberg 3 , Hemmo A. Abels 1
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Formation of alluvial stratigraphy is controlled by autogenic processes that mix their imprints with allogenic forcing. In some alluvial successions, sedimentary cycles have been linked to astronomically‐driven, cyclic climate changes. However, it remains challenging to define how such cyclic allogenic forcing leads to sedimentary cycles when it continuously occurs in concert with autogenic forcing. Accordingly, we evaluate the impact of cyclic and non‐cyclic upstream forcing on alluvial stratigraphy through a process‐based alluvial architecture model, the Karssenberg and Bridge (2008) model (KB08). The KB08 model depicts diffusion‐based sediment transport, erosion and deposition within a network of channel belts and associated floodplains, with river avulsion dependent on lateral floodplain gradient, flood magnitude and frequency, and stochastic components. We find cyclic alluvial stratigraphic patterns to occur when there is cyclicity in the ratio of sediment supply over water discharge (Qs/Qw ratio), in the precondition that the allogenic forcing has sufficiently large amplitudes and long, but not very long, wavelengths, depending on inherent properties of the modelled basin (e.g. basin subsidence, size, and slope). Each alluvial stratigraphic cycle consists of two phases: an aggradation phase characterized by rapid sedimentation due to frequent channel shifting and a non‐deposition phase characterized by channel belt stability and, depending on Qs/Qw amplitudes, incision. Larger Qs/Qw ratio amplitudes contribute to weaker downstream signal shredding by stochastic components in the model. Floodplain topographic differences are found to be compensated by autogenic dynamics at certain compensational timescales in fully autogenic runs, while the presence of allogenic forcing clearly impacts the compensational stacking patterns.
中文翻译：
通过基于过程的冲积体系结构模型评估冲积地层对循环和非循环上游强迫的响应
冲积地层的形成受自生过程控制，这些过程将其烙印与同生强迫相混合。在某些冲积演替中，沉积循环与天文学驱动的周期性气候变化有关。但是，定义这种循环同种异体强迫与自发强迫连续发生时如何导致沉积循环仍然是一项挑战。因此，我们通过基于过程的冲积体系模型Karssenberg and Bridge（2008）模型（KB08）评估了循环和非循环上游强迫对冲积地层的影响。KB08模型描述了河床带和相关洪泛区网络内基于扩散的沉积物输运，侵蚀和沉积，其中河流的侵蚀取决于横向洪泛区的坡度，洪泛大小和频率，和随机成分。我们发现，当沉积物供应量与排水量之比存在周期性时，就会出现周期性冲积地层模式（Q s / Q w之比），前提是同种作用强迫具有足够大的振幅和很长但不是很长的波长，具体取决于建模盆地的固有属性（例如盆地沉降，大小和坡度）。每个冲积地层周期由两个阶段组成：一个凝集阶段，其特征是由于频繁的河道移动而快速沉积；一个非沉积阶段的特征在于河道带的稳定性，并取决于Q s / Q w振幅，进行切割。Q s / Q w更大比率振幅会导致模型中的随机成分减弱下游信号。洪泛平原的地形差异被完全自生的运行在某些补偿时间尺度上的自生动力学所补偿，而同基因强迫作用的存在显然影响了补偿堆积模式。
更新日期：2020-04-11
中文翻译：
通过基于过程的冲积体系结构模型评估冲积地层对循环和非循环上游强迫的响应
冲积地层的形成受自生过程控制，这些过程将其烙印与同生强迫相混合。在某些冲积演替中，沉积循环与天文学驱动的周期性气候变化有关。但是，定义这种循环同种异体强迫与自发强迫连续发生时如何导致沉积循环仍然是一项挑战。因此，我们通过基于过程的冲积体系模型Karssenberg and Bridge（2008）模型（KB08）评估了循环和非循环上游强迫对冲积地层的影响。KB08模型描述了河床带和相关洪泛区网络内基于扩散的沉积物输运，侵蚀和沉积，其中河流的侵蚀取决于横向洪泛区的坡度，洪泛大小和频率，和随机成分。我们发现，当沉积物供应量与排水量之比存在周期性时，就会出现周期性冲积地层模式（Q s / Q w之比），前提是同种作用强迫具有足够大的振幅和很长但不是很长的波长，具体取决于建模盆地的固有属性（例如盆地沉降，大小和坡度）。每个冲积地层周期由两个阶段组成：一个凝集阶段，其特征是由于频繁的河道移动而快速沉积；一个非沉积阶段的特征在于河道带的稳定性，并取决于Q s / Q w振幅，进行切割。Q s / Q w更大比率振幅会导致模型中的随机成分减弱下游信号。洪泛平原的地形差异被完全自生的运行在某些补偿时间尺度上的自生动力学所补偿，而同基因强迫作用的存在显然影响了补偿堆积模式。
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