The Station is located at the southern end of the Northern Highlands geomorphic feature, which is west of the
Florahome Valley geomorphic feature and southeast of the base of the Trail Ridge geomorphic feature. Highland
areas often coincide with areas of high recharge for aquifers. Many highland areas have variably developed
karst features that allow for rapid infiltration of surface water (and pollutants) into the aquifer system
(Readle 1990, Scott 1992). The oldest Cenozoic era sediments in the area of the Station are the Cedar Keys
Formation, which have been dated at 55 to 65 million years before present. This formation is 1500 feet to
1700 feet below the National Geodetic Vertical Datum of 1929 (NGVD, formerly called mean sea level) and is
approximately 500 feet thick (Figure ). The top of the next layer lies approximately 1000 to 1200 feet below
NGVD and is known as the Oldsmar Formation. These two layers contain no potable water (Motz, et al. 1991 and
1992, Readle 1990, Scott 1992).
The Florida Aquifer occupies the next four layers of sediment. These have been named the Avon Park Formation and
the Ocala Group. All of these sediments from the Paleogene are dominated by dolomite and limestone. Layers from
the Oligocene are absent in Northeast Florida (Motz, et al. 1991 and 1992, Readle 1990, Scott 1992, Yobbi, et al. 1979).
The upper confining layer of the Floridan Aquifer is the Hawthorn Group. The top of the Hawthorn Group is estimated
at 0 feet to 100 feet above NGVD and is believed to be between 50 and 200 feet thick. The dominant sediments are
clastics of quartz sands and clays. There is very little potable water available in these sediments. Other layers
of the Neogene are thin or absent in western Putnam County (Bonoil, et al. 1993, Motz, et al. 1991 and 1992,
Readle 1990, Scott 1992, Yobbi, et al. 1979). Above this is a layer of unnamed sands that is sometimes described
as the Anastasia Formation. These sands form the soils of Putnam County. There is a shallow aquifer within
these sediments (Beadle 1990, Scott 1992).
- Bonoil, D., M. Williams, and D. Munch. 1993. Mapping recharge to the Floridan aquifer unsing a geographic information system. St. Johns River Water Management District, Technical Publication SJ93-5, Palatka, Florida. pp 41.
- Motz, L.H., J.P. Heaney, W.K. Denton, M.S. Fowler, and G. Leiter. 1992. Upper Etoniah Creek Hydrologic Study, Phase II Final Report. St. Johns River Water Management District, Technical Publication SJ92-SP18, Palatka, Florida. pp 414.
- Scott, T.M. 1992. A geological overview of Florida. Open File Report No.50. Florida Geological Survey, Tallahassee, Florida. pp78.
- Readle, E.L. 1990. Soil survey of Putnam county area, Florida. USDA, SCS. Pp 224.
- Yobbi, D.K. and G.C. Chappell. 1979. Summary of the Hydrology of the Upper Etonia Creek Basin. Edited by Frank W. Fenzel. Technical Publication SJ79-5. Water Resources Department, St. Johns River Water Management District, Palatka, Florida. pp 89.