Calcite cementation in the upper Floridan aquifer: A modern example for confined-aquifer cementation models?

Detailed petrographic study of the Oligocene Suwannee limestone (a principal unit of the upper Floridan aquifer system) indicates that all the calcite cements in the Suwannee limestone are precompaction in origin. Most are clearly associated with either early mineralogical stabilization or Oligocene subaerial exposure features. None of the cements are in isotopic (δ¹⁸O and δ¹³C) or trace element (Fe, Mn, and Sr) equilibrium with the extant aquifer waters. The cements therefore formed prior to the onset of regionally confined, freshwater aquifer conditions. These rocks have been basically inert with respect to calcite cementation during the past 5 to 10 m.y. while they have been part of the regional confined aquifer. Using this modern aquifer as an example, it is likely that confined paleoaquifer cementation has been overestimated as an explanation for regional cementation patterns in ancient limestones.