The Miami Limestone was deposited during the Sangamon interglacial, when southern Florida was under a shallow sea. The fossils in the formation underlying the Everglades, which does not include any ooids, consists primarily of a single bryozoan species, Schizoporella floridana. Based on those differences, Mitchel-Tapping divided the Miami Limestone into the Fort Dallas oolite on the mainland and under northern Florida Bay, and the Key West oolite, under southern Florida Bay and the lower Florida Keys. The oolitic formation in the lower Florida Keys has less quartz sand and fewer fossils than does the oolitic formation on the mainland. The part of the Miami Limestone forming the Atlantic Coastal Ridge and the lower Florida Keys is an oolitic grainstone which includes fossils of corals, echinoids, mollusks, and algae. Mitchell-Tapping also states that a component of the Miami Limestone extends under the Gulf of Mexico north to a point 112 kilometers west of Tampa. It also lies under the eastern (Miami-Dade County) part of the Everglades, Florida Bay, and the lower Florida Keys from Big Pine Key to the Marquesas Keys. Miami Limestone forms the Atlantic Coastal Ridge in southeastern Florida, near the coast in Palm Beach, Broward and Miami Dade counties. The Miami Limestone, originally called Miami Oolite, is a geologic formation of limestone in southeastern Florida. Miami Limestone (formerly Miami Oolite, orange on map) in relation to other formations in South Florida. Further development of this radar system and its application to groundwater investigations represents a significant advance in monitoring techniques and will lead to increased understanding of vadose zone flow.Geologic formation in Florida, USA Miami Limestone Our results demonstrate that GPR is capable of monitoring both individual rainfall events and seasonal moisture variation within the Miami Oolite, at a resolution far greater than that allowed by alternative methods. The time-shift data indicate varying levels of rock saturation, and the amplitude changes show the locations of ponded water layers and active flow paths. In radar images, varying moisture contents are visible as both time-shifts and amplitude changes. This gives rise to significant time-shifts even at lower saturations. Porosity in the Miami Oolite ranges from 0.4 to over 0.6 and calculations using the Topp equation show that for this medium, radar velocities may easily halve as the moisture content approaches saturation. As site geology remains constant, any variation in the 3D radar image is due to changes in water content. Applying the new radar to hydrological investigation introduces the possibility of monitoring the migration of moisture pulses, as the system enables precise relocation of the radar antennae and repetition of surveys several times per day. These dense 3D volumes accurately image the complex sedimentary structure of the Miami Oolitic Limestone. We present first field trials with a new full-resolution 3D radar system which allows the rapid acquisition of precisely located and repeatable radar grids, with cell size of 5-10 centimetres, over sites larger than a thousand square meters. However, its true potential has been restricted because conventional 2D and pseudo 3D GPR images are distorted by out-of-plane reflections and interpolation artefacts. Ground Penetrating Radar (GPR) has the capacity to image aquifer structure and dynamics at a sub-meter scale. Data available at present rely either on interpolation between point measurements, or `broad brush' geophysical methods which lack the resolution to exactly define how or where moisture pulses migrate to the water table. Despite implications for groundwater vulnerability and aquifer recharge, the anatomy of vadose zone flow-paths and ponded water layers remains largely unknown.
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