Episodic overbank deposition as a dominant mechanism of floodplain and delta-plain aggradation
Episodic overbank deposition as a dominant mechanism of floodplain and delta-plain aggradation
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DOI：
10.1130/g36847.1
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发表时间：
2015-10
期刊：
影响因子：
5.8
通讯作者：
Zhixiong Shen;T. Törnqvist;B. Mauz;E. Chamberlain;A. Nijhuis;L. Sandoval
中科院分区：
文献类型：
--
作者：
Zhixiong Shen;T. Törnqvist;B. Mauz;E. Chamberlain;A. Nijhuis;L. Sandoval
泛滥频繁导致泛滥平原和三角洲平原上的冲积层逐渐堆积的普遍观点受到了各种研究的挑战，这些研究表明，泛滥是以强烈的间歇性方式发生的。然而，由于很难建立足够高分辨率的年龄模型，这在很大程度上仍然是一个未经检验的假设。在这里，我们使用39个来自密西西比三角洲近岸岸上沉积的光激发发光(OSL)年龄首次证明，从百年到千年的时间尺度上的冲积沉积主要是幕式的，沉积速率为1-4厘米/年，可以持续几个世纪。来自三个不同研究地区的OSL年龄产生了截然不同但相辅相成的年龄群。这些发现表明，大陆地层记录的很大一部分是由相对离散的百年至千年规模的沉积体拼凑而成的，这些沉积体是由自生过程组装而成的。
The common view that frequent overbank flooding leads to gradual aggradation of alluvial strata on floodplains and delta plains has been challenged by a variety of studies that suggest that overbank aggradation occurs in a strongly episodic fashion. However, this remains a largely untested hypothesis due to the difficulty in establishing age models with sufficiently high resolution. Here we use 39 optically stimulated luminescence (OSL) ages from proximal overbank deposits in the Mississippi Delta to demonstrate for the first time that alluvial aggradation over centennial to millennial time scales is predominantly episodic, with aggradation rates of 1–4 cm/yr that can persist for centuries. OSL ages from three separate study areas produce age clusters that are distinctly different yet complement each other. These findings suggest that a substantial portion of the continental stratigraphic record consists of patchworks of relatively discrete, centennial- to millennial-scale sediment bodies assembled by autogenic processes.