Graduation Year


Document Type




Degree Name

Doctor of Philosophy (Ph.D.)


Materials Science

Degree Granting Department

Marine Science

Major Professor

William M. Sackett, Ph.D.

Committee Member

Sam B. Upchurch, Ph.D .

Committee Member

Robert H . Byrne, Ph .D.

Committee Member

Kent A. Fanning, Ph.D.

Committee Member

Edward S. VanVleet, Ph .D.


Stable isotopic compositions of oxygen, carbon, and hydrogen were used to identify the sources of water and of organic matter, pathway reactions, evaporation processes, and transfer mechanisms among various water types as well as the extent of water-rock reactions. An attempt to understand the isotopic compositions of the hydrological cycle of west-central Florida, their variations, baseline levels and controlling mechanisms constitutes parts of this dissertation.

A comparison of δ18O in rainwater (weighted mean = -4.4 o/oo) and surficial ground water (mean = -4.1 o/oo) indicates that rainwater recharges the surficial aquifer with only a minor isotopic change. δ18O vs δD plots of rainwater and ground waters suggest that recently recharged water in the upper Floridan aquifer is similar to today's rainwater. As shown by calculations, carbonate aquifers react extensively with the ground waters in the upper Floridan aquifer through time to cause a shift of δ18O from -4.4 to -2.8 o/oo. Changes in δ18O and δ13CDIC in ground waters of the upper Floridan aquifer in two flow paths suggest that the confined nature of the aquifer causes the difference. Parts of the upper Floridan aquifer supply freshwater to rivers discharging into Tampa Bay as evidenced by similarities in δ180 and δ13CDIC of both freshwater types. Evaporation may play a role in shifting the δ18O of rivers from ground-water source of -2.8 o/oo to -2.3 o/oo.

δ18O and δ13C in Tampa-Bay water correlate linearly with salinity. Based on isotopic mass balance calculations, the replacement time of Tampa-Bay water is about 67 days. Mirror Lake has invariant δ18O during a one-year study, and has a calculated replacement time for its water of 43 days.