At S10C, sediments generally are poorly sorted and the d₂₀ in the complete borehole (Fort Thompson and Tamiami Formations) ranges from 0.12 mm (very fine) to 0.46 mm (medium). Various cycles of coarsening upwards and fining upwards appear in the S10C profile, which indicates periods of sea-level transgression and regression (fig. 8). In contrast, sediments from ENR site MOP2 have a d₂₀ that ranges from 0.11 mm (very fine) to 0.25 mm (fine/medium) and primarily are well sorted. The ENR profiles show much smaller changes with elevations (fig. 7). The geometric mean of d₁₀, d₁₇, d₂₀, and d₆₀ values and the uniformity coefficient (C_u) are all larger for WCA-2A compared with the ENR boreholes. Possible sub-areal caps and caliche crusts are present in the limestone core samples at varying depths and are described in Harvey and others (2000, p. 94 and 98).

These sedimentary differences support the theory that the depositional environments at WCA-2A were different than those at the ENR (Enos, 1977). This difference probably resulted because the ENR is located about 20 mi north of and slightly west of WCA-2A. Whereas both sites have similar land-surface elevations, WCA-2A is closer to the current and paleo-shorelines of peninsular Florida and would have been flooded earlier, longer, and possibly more frequently by sea-level transgressions and regressions. Because of the changing sea levels, the chemical composition of the water within the aquifer and the depositional processes varied. Future work could involve correlating the sub-aereal caps and caliche crusts and the effect of these sedimentary structures on ground-water quality.

Figure 7. Uniformity coefficients, hydraulic conductivities from drawdown tests, and generalized lithology from the Surficial aquifer at sites MP2 (ENR) (top, A) and S10C (WCA-2A) (bottom, B), north-central Everglades, south Florida. [larger version]

Figure 8. Grain size from the Surficial aquifer at site S10C (WCA-2A) and site MOP2 (ENR), north-central Everglades, south Florida. [larger version]