The Origin of Badwater in the Edwards Aquifer, Texas: An Integrated Approach to Regional Flow Systems in a Carbonate Aquifer

本研究旨在评估区域碳酸盐含水层（德克萨斯州爱德华兹含水层）天然含盐地下水的形成过程。这些水存在于当地所谓的坏水区（盐度大于1000毫克/分）。尽管该含水层的环境重要性和许多先前的研究，关于坏水带水化学相的起源和演化的假设仍然众多和推测。这项研究将综合使用一系列传统的和新开发的分析技术，对爱德华兹含水层进行水文和地球化学研究，研究范围包括沿坏水带和淡水带之间的边界和正常边界。该数据库将包括将在新样品上获得的电位测定和主元素（稀土元素）、稳定同位素（H、O、B、S）和放射性同位素（Sr、Nd、U和Ra）数据。本研究还将包括对构成含水层的下白垩统碳酸盐岩的岩石学和地球化学分析。这些数据将用于模拟流体流动、流体-岩石相互作用和含水层内流体混合的定量模型。待研究的元素和同位素参数具有广泛的地球化学行为，这对于应用理论模型来约束五种不同水化学相的起源过程至关重要。这项研究将有助于我们对墨西哥湾沉积盆地区域流动系统的理解，并将对区域碳酸盐含水层发育和含盐地下水演化的化学和构造控制产生更广泛的影响。

This research seeks to evaluate the processes responsible for natural saline groundwaters in a regional carbonate aquifer--the Edwards aquifer of Texas. These waters are present in what is locally referred to as the badwater zone (salinities of greater than 1000 mg/1). Despite the environmental importance of this aquifer and many previous studies here, hypotheses for the origin and evolution of the badwater zone hydrochemical facies remain numerous and speculative. This research will integrate a range of conventional and newly developed analytical techniques in a hydrological and geochemical study of the Edwards aquifer both along and normal to the boundary between the badwater and freshwater zones. The data base will include potentiometric and major-element (rare-earth elements), and stable (H, O, B, S) and radiogenic (Sr, Nd, U and Ra) isotope data that will be acquired on new samples. This study will also include petrologic and geochemical analyses of lower Cretaceous carbonate rocks that constitute the aquifer. These data will be used in quantitative models that simulate fluid flow, fluid-rock interaction, and fluid mixing within aquifers. The elemental and isotopic parameters to be studied have a wide range of geochemical behavior, which will be critical for the application of theoretical models to constraining the processes involved in the origin of each of five distinct hydrochemical facies. This study will bear on our understanding of regional flow systems in the Gulf of Mexico sedimentary basin, and will have broader implications for the chemical and structural controls on the development of regional carbonate aquifers and the evolution of saline groundwaters.