Abstract
Excerpt: A 3-year investigation of the shallow, unconfined Coral Reef Aquifer of northern Collier County, Florida, has revealed the relationship of carbonate lithofacies to the transmissivity and specific yield of the aquifer. The geology of the aquifer was studied using cores, test wells, and both surface and borehole geophysics. Numerous aquifer performance tests were conducted to measure the hydraulic coefficients of the aquifer. The Coral Reef Aquifer consists of a surficial quartz sand mantel from 4 to 20 feet thick underlain by 24 to 70 feet of limestone. Four predominant lithofacies were found in the limestone: moldic arenaceous, molluscan packstone; corraline, moldic boundstone,; molluscan wackestone; and unconsolidated, agrillaceous wackestone. The base of the aquifer is formed by a low permeability, green dolosilt. Transmissivity values measured over a 12-square mile area ranged from 59,000 to 1,550,000 gpd/ft. The highest transmissivity values were associated with the occurrence of molluscan packstones. Estimated porosities in the molluscan packstone ranged up to 65% compared to 40% or less in the other lithofacies. The transmissivity of the aquifer was dependent primarily on the occurrence of the molluscan packstones and not greatly dependent on the overall aquifer thickness.