COLLABORATIVE RESEARCH: Experimental Study of Basin Stratigraphy

9725471 Pratson我们提出了一个为期三年的物理地层学形成实验研究计划，利用圣安东尼瀑布实验室的一个新的大型实验盆地进行实验研究。这一设施允许研究尺度盆地过程，完全控制基准面、沉积物供应，特别是沉降模式和速率。水池长13米，宽6.5米，最大可容纳1.3米的空间来存放。下沉地板包括432个独立可控的下沉单元，以蜂窝形式排列。这种设计允许创建几乎无限范围的空间和时间下沉模式。泥沙和水可以从盆地边缘的任何地方补给，基准面(即水位)是独立可控的。我们的初步实验将旨在检验已提出的盆地规模物理地层学形成模型的一些一阶预测，例如：(1)海岸线迁移和相关地层学与沉降速率和海平面之间的相互作用的关系；(2)沉降速率和几何形状以及泥沙供应对冲积粗相分布(即同构造砾石的起源)的控制；以及(3)沉降速率和泥沙供应对冲积结构发育的影响。初步结果表明，这些实验还可以提供对生长断层等过程的洞察，这些过程尚未被广泛纳入现有模型。这些实验将使用相对简单的下沉和进沙几何形状，并将重点展示“单位”地层对一个或最多两个变量同时变化的响应。第二组实验将集中在下沉和泥沙供应方面的三维效应，包括：1)基准面变化的三维效应；2)与盲冲和递进不整合有关的近端盆地中的活动褶皱的传播；3)横向和轴向排水相结合的不对称半地堑中的沉积。实验的主要产品将包括：施加变量(水和泥沙供应、基准面和基底地形)的时间记录；随时间推移的床面地形测量；流型、海岸线位置和其他地表特征的视频记录；所产生的沉积物的三维框图，既有直接数字化的(照相)图像，也有合成的地震图像；以及选定剖面的合成地球物理记录。合成地震是野外观测的关键环节，因为研究人员能够获得可与实验盆地产生的岩石记录相媲美的岩石记录的唯一方法是通过地震反射剖面的过滤。合成地震学和测井与实际实验地层学的对比，也将促进我们对岩石记录通过这些广泛使用的技术成像时保留什么和不保留什么的理解。这些实验结果将是首次在完全受控的条件下检验自皮特曼(1978)的海岸线对海平面变化的响应模型以来发展起来的各种地层响应理论预测。它们还将提供一个模板，可以与基于地震和露头数据的实地观察和解释相比较。尽管实验室规模的模型永远不能捕捉到真实盆地中发生的所有复杂过程，但它们在未经测试的理论模型和难以约束的自然例子之间起到了桥梁作用。

9725471 Pratson We propose a three-year program of experimental studies o the formation of physical stratigraphy, using a large new experimental basin with a subsiding floor at the St. Anthony Falls Laboratory (SAFL). This facility allows study of scaled basin processes with complete control of base level, sediment supply and, especially, subsidence pattern and rate. The basin is 13m by 6.5m and allows up to 1.3m of accommodation space for deposition. The subsiding floor comprises 432 independently controllable subsidence cells arranged in a honeycomb pattern. This design allows the creation of a nearly unlimited range of spatial and temporal subsidence patterns. Sediment and water can be fed from anywhere along the basin margin and base level (i.e. water level) is independently controllable. Our first experiments will be aimed at testing some of the first-order predictions of models that have been proposed for formation of physical stratigraphy at basin scales, such as: (1) the relationship of shoreline migration and associated stratigraphy to the interplay between subsidence rate and eustatic sea level; (2) the control of subsidence rate and geometry, and sediment supply, on alluvial coarse-facies distribution (i.e. the origin of syntectonic gravel's); and (3) the influence of subsidence rate and sediment supply on the development of alluvial architecture. Initial results suggest that the experiments can also provide insight on processes such as growth faulting that have not been widely incorporated into existing models. These experiments will use relatively simple subsidence and sediment-feed geometries and will focus on demonstrating "unit" stratigraphic response to changes in one or at most two variables simultaneously. The second set of experiments will focus on 3-D effects in both subsidence and sediment supply, including: 1) 3-D effects of base-level change; 2) propagating active folding in the proximal basin associated with blind thrusts and development of progressive unconformities; 3) sedimentation in an asymmetric half graben combining both transverse and axial drainage. The principal products of the experiments will include: time records of the imposed variables (water and sediment supply, base level, and basement topography); measurements of bed-surface topography through time; video records of flow pattern, shoreline position and other surface features; 3-D block diagrams of the resulting deposits, presented both as directly digitized (photographic) and synthetic seismic images; and synthetic geophysical logs of selected profiles. The synthetic seismics are a crucial link with field observations, since the only way that researchers can obtain views of the rock record comparable to those generated by the experimental basin is through the filter of seismic reflection profiling. The synthetic seismics and well logs, when contrasted against the actual experimental stratigraphy, will also advance our understanding of what is and is not retained from the rock record when it is imaged via these widely used techniques. The experimental results would represent the first test under fully controlled conditions of a wide variety of theoretical predictions of stratigraphic response that have been developed since Pitman's (1978) model of shoreline response to changing sea level. They would also provide a template that could be compared with field observations and interpretations based on seismic and outcrop data. Although laboratory scale models can never capture all of the complex processes that occur in real basins, they serve as a bridge between untested theoretical models and difficult-to-constrain natural examples.