Multi-Scale Heterogeneity of the Stream-Dominated Alluvial Fan: New Perspective and Implications for Transport

9870342雾虽然流为主的冲积扇包括一个重要的含水层系统的比例很大，这些存款的详细的三维特征是显着缺乏在文献中。 层序地层学概念在石油研究中成功地应用于预测地下相分布，这有力地表明，当对纯陆相地层进行修改时，层序地层学可以用于表征冲积扇系统。 该项目融合了水文学、地质学、地球物理学和土壤学等多个学科，以建立一个层序地层框架，从而为典型的以河流为主的冲积扇提供一个更先进、更易于处理的非均质性模型。 这项研究的意义有三个方面。 首先，通过发展陆相层序地层学概念，它将为我们理解许多冲积扇地下水系统的非均质性创造一些必要的“秩序”。 其次，这项研究将提供一种方法，将地质统计模拟纳入层序地层框架，从而提供含水层系统的详细特征。 最后，这项研究将提供一个很大的进步，我们的能力，以表征和模拟区域地下水流和运输的许多类型的冲积矿床。 这样的进步是迫切需要的估计农业和城市污染对地下水quality.Central的可持续性的长期影响，拟议的研究是识别序列，与第四纪气候周期，横向广泛的，成熟的古土壤为界。 这些古土壤标志着间冰期期间的扇暴露，并在含水层系统中形成横向广泛的弱透水层。 地层序列内的沉积发生在风扇上的冰川事件，当住宿空间是由增加流量和沉积物供应。 在这些层序中，体系域（例如，在Kings River Fan的岩芯、钻井日志和地貌制图中也发现了在气候循环的一个时间段内沉积的岩相组合。 建议在特定体系域（例如，下切河谷充填沉积物），以检查这些差异。 将通过环境磁学、相形态学和岩相学分析对体系域进行比较。 将相对丰富的钻井记录与岩心数据进行校准（已在国王河冲积扇的其他部分成功完成），将提供一种确定地下系统域几何形状的方法。 一种新的马尔可夫链技术，用于地质统计学建模的空间分布在沉积单元具有更大的地质严格性（卡尔和福格，1996年a，1997年）将被用来产生随机模拟的结构单元的层序地层框架内。

9870342FoggThough stream-dominated alluvial fans comprise a large percentage of important aquifer systems, detailed three-dimensional characterizations of these deposits are notably lacking in the literature. Successful application of sequence stratigraphic concepts in petroleum research to predict subsurface facies distributions strongly suggests that, when modified for purely continental strata, sequence stratigraphy can be applied to characterize alluvial fan systems. This project involves the fusion of several disciplines, including hydrology, geology, geophysics, and soil science, to develop a sequence stratigraphic framework from which a more advanced, tractable model of heterogeneity can be produced for typical, stream-dominated alluvial fans. Significance of this research is three-fold. First, it will create some needed "order" in our understanding of heterogeneity in many alluvial fan groundwater systems through development of continental sequence stratigraphic concepts. Second, the research will provide a method to incorporate geostatistical simulation into a sequence stratigraphic framework, thus providing a detailed characterization of the aquifer system. Finally, the research will provide a large step forward in our ability to characterize and model regional groundwater flow and transport in many types of alluvial deposits. Such an advance is sorely needed for estimating long-term impacts of agricultural and urban pollution on sustainability of groundwater quality.Central to the proposed research is the recognition of sequences, related to Quaternary climate cycles, bounded by laterally extensive, mature paleosols. These paleosols mark fan exposure during interglacial periods, and form laterally extensive aquitards in the aquifer system. Strata within the sequences represents deposition that occurred on the fan during glacial episodes, when accommodation space was made available by increased discharge and sediment supply. Within these sequences, systems tracts (e.g., linked assemblage of lithofacies deposited during one time period of the climatic cycle) have also been recognized in core, driller's logs, and geomorphic mapping of the Kings River fan. It is proposed that additional continuous core will be collected specific systems tracts (e.g., incised valley fill deposits) to examine these differences. The systems tracts will be compared through use of environmental magnetism, facies morphology, and petrographic analysis. Calibration of relatively abundant drillers logs to the core data, already successfully accomplished in other portions of the Kings River alluvial fan, will provide a means to define systems tract geometry in the subsurface. A new Markov-chain technique for geostatistical modeling of spatial distribution in sedimentary units with greater geologic rigor (Carle and Fogg, 1996a, 1997) will be used to produce stochastic simulations of textural units within the sequence stratigraphic framework.