Jennings Bluff Tract State Geological Site, Cedar Keys Formation, and Madison Blue Spring –FGS News and Research 2023-05-01

The May 2023 issue of FGS News and Research by the Florida Geological Survey has several articles relevant to the Suwannee River Basin.

[FGS N&R Madison Blue Spring]
FGS N&R Madison Blue Spring

On the Alapaha River Water Trail, Jennings Bluff Tract in Hamilton County Named as the Seventh State Geological Site covers what we reported from the site at the announcement. See also Alapaha Swallets Dye Trace Project 2016-10-01.

Down at the Estuary, there’s Featured Formation: Cedar Keys Formation.

If you think you might have a spring, there’s A Guide to Identifying Springs and Seeps in Florida.

And on the Withlacoochee and Little River Water Trail, there’s a favorite spring: Geology in …the Real Florida™ —Madison Blue Spring State Park.

Madison Blue Spring State Park provides a wide variety of recreational activities including swimming, picnicking, hiking, paddling and scuba diving. The park includes Madison Blue Spring, that discharges to the Withlacoochee River, and numerous other karst features. The crystal blue waters of Madison Blue Spring are world famous for underwater cave diving and exploration, while the Withlacoochee River provides ample opportunities for kayaking and canoeing.

[Madison Blue Spring flowing into the Withlacoochee River (view is to the east)]
Madison Blue Spring flowing into the Withlacoochee River (view is to the east)

w The park, located in easternmost Madison County on the west bank of the Withlacoochee River, lies approximately 12 miles north of the confluence of the Withlacoochee and Suwannee rivers. Madison Blue Spring, one of 33 first magnitude springs in Florida, flows from an 80-foot diameter spring pool, down a 100-foot spring run and into the Withlacoochee River. A large opening about 30 feet below the surface of the spring leads to an extensive underwater cave system. Over 26,000 feet of passages have been mapped by certified cave divers, making it one of the longest underwater caves systems in the state. The cave system extends well outside of the park boundary and passes under the Withlacoochee River just south of the State Road 6 bridge.

The spring’s clear blue waters originate from the lower Oligocene Suwannee Limestone, part of the Floridan aquifer system. The Suwannee Limestone, which is a white to cream-colored fossiliferous limestone, crops out in the Withlacoochee River and in the spring. The Suwannee Limestone is the upper geologic formation within the Floridan aquifer system throughout the park. The fossil sea biscuit Ryncholampas gouldii is an index fossil for the Suwannee Limestone and is commonly found in outcrops of the formation like seen in Madison Blue Spring and along the Withlacoochee River. An index fossil is a special fossil that is found only in a singular formation and helps geologists easily identify the formation and its geologic age. Agatized coral is another unique fossil that can be found at the confluence of the Withlacoochee River and Madison Spring’s waters in the gravelly bed of the river.

[Fossil examples]
Fossil examples

In the area surrounding Madison Blue Spring and to the west, the Suwannee Limestone is overlain by the lower Miocene Torreya Formation of the Hawthorn Group. The Torreya Formation is typically a siliciclastic unit with increasing amounts of carbonate in the lower part. Most of the exposures of Torreya Formation in the park are the siliciclastic portions, which vary from white to light gray to bluish gray, slightly clayey sands. The Torreya Formation is overlain by the Pliocene Miccosukee Formation, which forms the tops of many hills in the area. The Miccosukee Formation is a grayish-orange to grayish-red mottled clay, sand and gravel unit. In most of the upland areas of the park, the Miccosukee Formation is overlain by a thin (generally less than 20 feet thick) layer of undifferentiated Quaternary sands and clays.

Contact: Rick Green, P.G.


Green, R.C., Paul, D.T., Petrushak, S.C., Kromhout, C., and Scott, T.M., 2007a, Geologic Map of the Eastern Portion of the USGS Perry 30 x 60 Minute Quadrangle, Northern Florida: Florida Geological Survey Open-File Map Series 98, 3 plates

Green, R.C., Paul, D.T., and Scott, T.M., 2007, Text to Accompany the Geologic Map of the Eastern Portion of the USGS Perry 30 x 60 Minute Quadrangle, Northern Florida: Florida Geological Survey Open-File Report 91, 32p.

Gulden, B., and Coke, J., 2022, World’s Longest Underwater Caves. Website accessed on Feb. 15, 2023.

Scott, T.M., Means, G.H., Meegan, R.P., Means, R.C., Upchurch, S.B., Copeland, R.E., Jones, J, Roberts, T., and Willet, A., 2004, Springs of Florida: Florida Geological Survey Bulletin 66, 377p.

Thanks to WWALS Science Committee Chair Dr. Tom Potter for spotting this issue.

 -jsq, John S. Quarterman, Suwannee RIVERKEEPER®

You can help with clean, swimmable, fishable, drinkable, water in the 10,000-square-mile Suwannee River Basin in Florida and Georgia by becoming a WWALS member today!