Approximate Eastern Limit of the Gray Limestone Aquifer in Broward County, USGS WRIR 87-4034, figure 36

An investigation of the surficial aquifer system in Broward County, begun in 1981, is part of a regional study of the aquifer system in southeast Florida. Test drilling for lithologic samples, flow measurements taken during drilling, aquifer testing, and analyses of previously available data permitted delineation of the permeability framework (on geologic sections), the aquifers in the system and the generalized transmissivity distribution, and interpretation of the ground-water flow system. In addition to the Biscayne aquifer, a previously undefined aquifer, composed of gray (in places, greenish-gray or tan) limestone of the lower part and locally the middle part of the Tamiami Formation, was found at depth in west Broward County. Although it is less permeable than the Biscayne aquifer, the gray limestone is nevertheless a significant aquifer and a potential source of water. The aquifer is informally and locally named as the gray limestone aquifer. It is defined as that part of the limestone beds (usually gray) and contiguous coarse clastic beds of the lower to middle part of the Tamiami Formation that are highly permeable (having a hydraulic conductivity of about 100 ft/d or more) and at least 10 feet thick. Above and below the gray limestone aquifer in west Broward County and separating it from the Biscayne aquifer and the base of the surficial aquifer system are sediments having relatively low permeability, such as mixtures of sand, clay, silt, shell, and lime mud, and some sediments of moderate to low permeability, such as limestone, sandstone, and claystone. Subsequent drilling has traced the gray limestone aquifer into southwest Palm Beach County where the water contains high dissolved solids and into northwest Dade County where the water generally has low dissolved solids. The aquifer probably extend westward into Collier County, and it likely is the source of water for irrigation and drinking on the Seminole Indian Reservation and sugar cane fields of southeast Hendry County. The map shows the approximate eastern limit of the gray limestone aquifer in Broward County.1981年启动的布劳沃德县（Broward County）表层含水层系统（surficial aquifer system）调查，是佛罗里达州东南部含水层系统区域研究的组成部分。本次研究通过获取岩性样本（lithologic samples）的钻探作业、钻进过程中的流量测量、含水层试验（aquifer testing），以及对已有历史数据的分析，得以完成地质剖面维度的渗透框架（permeability framework）圈定、系统内含水层划分与概化导水系数分布（transmissivity distribution）刻画，并实现了地下水流系统（ground-water flow system）的解译。 除比斯坎含水层（Biscayne aquifer）外，研究团队在布劳沃德县西部深部地层中发现了此前未被界定的含水层：该含水层由塔米亚米组（Tamiami Formation）下部（局部包含中部地层）的灰色（部分区域呈灰绿色或黄褐色）石灰岩构成。尽管其渗透性弱于比斯坎含水层，但该灰色石灰岩仍是重要的供水含水层与潜在水源。该含水层被非正式地以当地通用称谓命名为灰色石灰岩含水层（gray limestone aquifer），其定义为塔米亚米组下部至中部的灰色石灰岩地层及其相邻粗碎屑岩地层中，导水率（hydraulic conductivity）约100英尺/天（ft/d）及以上、厚度至少10英尺的高渗透段。在布劳沃德县西部，该灰色石灰岩含水层的上下方均分布着渗透性相对较低的沉积物（如砂、黏土、粉砂、贝壳与石灰泥混合物），以及部分中低渗透性沉积物（如石灰岩、砂岩与泥岩），这些沉积物将灰色石灰岩含水层与比斯坎含水层及表层含水层系统基底分隔开来。 后续钻探追踪结果显示，灰色石灰岩含水层延伸至棕榈滩县（Palm Beach County）西南部，该区域含水层水体溶解固体（dissolved solids）含量偏高；同时延伸至戴德县（Dade County）西北部，该区域水体溶解固体含量普遍偏低。该含水层大概率向西延伸至科利尔县（Collier County），并极有可能为塞米诺尔印第安人保留地（Seminole Indian Reservation）以及亨德里县（Hendry County）东南部的甘蔗田提供灌溉与饮用水源。 本地图展示了布劳沃德县内灰色石灰岩含水层的大致东界范围。