Significance of channel-belt clustering in alluvial basins
Significance of channel-belt clustering in alluvial basins
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DOI：
10.1130/g30783.1
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发表时间：
2010-06-01
期刊：
影响因子：
5.8
通讯作者：
Sheets, Benjamin A.
中科院分区：
文献类型：
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作者：
Hajek, Elizabeth A.;Heller, Paul L.;Sheets, Benjamin A.
冲积盆地中河道沉积物的分布通常用于解释过去的气候、构造和海平面的变化。在这里，我们提出了初步证据，表明河流系统中的长期尺度（类似于 10(3)-10(5) 年）自组织可能会在没有变化的盆地边界条件或独立于变化的盆地边界条件的情况下自发地生成结构化地层图案。物理实验和古代冲积层序（费里斯组，白垩纪-古近纪晚期，怀俄明州中南部）都显示出地层，其中许多紧密间隔的河道沉积物群被大范围的河岸泥岩间隔开。使用空间点过程方法的分析表明，两个盆地的河道沉积物在统计上聚集在中间盆地长度尺度上。在实验中，外部控制（基准面、沉降率和沉积物/供水）没有变化，因此不是簇形成的因素。同样，古代系统缺乏对河道聚集的外部控制的地层学和沉积学证据。我们认为，正如本研究中所看到的，河道群反映了河流自组织的规模，而这在古代沉积物中通常是不被认识到的。在重建古代盆地充填物的构造、气候和海平面变化以及在露头带或地下井之间进行关联时，应考虑这种类型的内部生成地层。
The distribution of channel deposits in alluvial basins is commonly used to interpret past changes in climate, tectonics, and sea level. Here we present preliminary evidence that longtime scale (similar to 10(3)-10(5) yr) self-organization in fluvial systems may generate structured stratigraphic patterns spontaneously, in the absence of, or independent from, changing basin boundary conditions. A physical experiment and an ancient alluvial succession (Ferris Formation, latest Cretaceous-Paleogene, south-central Wyoming) both show stratigraphy where clusters of many closely spaced channel deposits are separated from each other by extensive intervals of overbank mudstones. Analysis using spatial point process methods shows that channel deposits in both basins are statistically clustered over intermediate basin length scales. In the experiment, external controls (base level, subsidence rate, and sediment/water supplies) were not varied, and therefore not factors in cluster formation. Likewise, the ancient system lacks stratigraphic and sedimentologic evidence of external controls on channel clustering. We propose that channel clusters, as seen in this study, reflect a scale of fluvial self-organization that is not usually recognized in ancient deposits. This type of internally generated stratigraphy should be considered when reconstructing tectonic, climate, and sea-level changes from ancient basin fills and when correlating between outcrop belts or subsurface wells.