Scale-dependent compensational stacking: An estimate of autogenic time scales in channelized sedimentary deposits
Scale-dependent compensational stacking: An estimate of autogenic time scales in channelized sedimentary deposits
复制标题
尺度相关的补偿堆积：渠道化沉积物自生时间尺度的估计
作者：
Yinan Wang;K. Straub;E. Hajek
最近的研究表明，保存在地层记录中的古环境（异体）信号可能被内部生成（自生）沉积污染或覆盖。这是有问题的，但目前还不清楚在什么时间和空间尺度的自生模式是最普遍的。我们建议，规模的变化，盆地填充趋势，可以用来确定之间的过渡，他源和自生地层。利用数值和物理实验的数据和一个古老的露头，我们探讨了补偿，沉积物输送系统的倾向，优先填充地形低点，随地层尺度的变化。基于对象的模型显示了地层从部分受自生过程影响到完全受他生作用决定的时间尺度，并表明这种转变发生在由运输系统中表面粗糙度的最大尺度除以长期沉积速率所确定的时间尺度上。这一假设在一个物理实验中得到验证，其中三角洲地形监测沿着流垂直断面在一个高的时间分辨率相对于通道kine matics。实验中的补偿强度在预测的时间尺度上变化，其中最大表面粗糙度等于实验通道的深度。在该补偿时间尺度之上，沉积物纯粹补偿地堆叠，但在该时间尺度之下，沉积物在随机和确定性之间的某个地方堆叠。在Ferris组（美国怀俄明州汉纳盆地古近系）中也观察到类似的尺度相关叠加。研究表明，尺度相关的补偿叠加可能有助于分离沉积盆地中的自生地层和他生地层。
Recent studies show that paleoenvironmental (allogenic) signals preserved in the stratigraphic record may be contaminated or overprinted by internally generated (autogenic) sedimentation. This is problematic, but it is unclear over what temporal and spatial scales autogenic patterns are most prevalent. We propose that scale breaks in basin-fi lling trends can be used to identify the transition between allogenic and autogenic stratigraphy. Using data from numerical and physical experiments and an ancient outcrop, we explore how compensation, the tendency for sediment transport systems to preferentially fi ll topographic lows, varies with stratigraphic scale. Object-based models demonstrate the temporal scales at which stratigraphy changes from being partially infl uenced by autogenic processes to being completely determined by allo- genic forcings and suggest that this transition occurs at a time scale set by the maximum scale of surface roughness in a transport system divided by the long-term aggradation rate. This hypothesis is validated in a physical experiment where delta topography was monitored along fl ow-perpendicular transects at a high temporal resolution relative to channel kine matics. The strength of compensation in the experiment changes at the predicted time scale, where the maxi mum surface roughness is equal to the depth of the experimental channels. Above this compensation time scale deposits stack purely compensationally, but below this time scale deposits stack somewhere between randomly and deterministically. Similar scale-dependent stacking is also observed in the Ferris Formation (Cretaceous-Paleogene, Hanna Basin, Wyoming, United States). This study demonstrates that scale-dependent compensational stack- ing may be useful for isolating allogenic and autogenic stratigraphy in sedimentary basins.