Our interview with Dr. Chris Werner was a mix of adventure, discovery, and hard science. Chris is director of the Woodville Karst Plain Project (WKPP), and a scuba diver who maps out unexplored caves in the Wakulla Spring system. It’s dangerous work in a setting most humans will never see in person.
The WKPP has recently shifted its focus to conduct more research along with their explorations. Our Coast to Canopy episode with Chris covered both aspects, and gave me a new understanding about the way water moves beneath our feet. It’s not the first interview I’ve said this about, and it won’t be the last. The Floridan Aquifer is vast and mysterious, and the answer to any question about it will inevitably spawn new questions.
As I’ve done for many Coast to Canopy episodes, I’ve split the written blog post version in two. This post is for people who want to understand the geology of the Floridan Aquifer in our area. We get geeky with geologic formations and Florida’s past as a shallow ocean. This post is specifically about the geology beneath our feet in Tallahassee and its surrounding counties.
The other post will focus on exploration, and how the WKPP is trying answering questions about the water that flows out of Wakulla Spring. North America’s largest spring is fed by many sources, and those can change over time. Can chemistry answer the question of Wakulla Spring’s dark water? Does water that goes into one sinkhole always come out from the same spring?
Meet our guest: Chris Werner
Dr. Christopher Werner is the Project Director of the Woodville Karst Plain Project. He received a bachelor’s degree in geology and planetary science from the University of Pittsburgh, with a minor in physics and math. He came to Florida because he wanted to dive in our area’s cave systems, and received his master’s in geology from Florida State University. After a career in the oil and gas industry, he returned to FSU to earn a Ph.D. in geophysical fluid dynamics. He has served as the Scientific Director of the Woodville Karst Plain Project since 1999.
Coast to Canopy blog posts are curated transcripts. My notes appear in italics.
Woodville Karst Plain: layers of limestone formations
Chris starts by explaining the geologic formations that make up the Woodville Karst Plain. We break it down further in the maps below.
Chris Werner: The Woodville Karst Plain is essentially an exposed limestone plain near the coast, where the Hawthorn Group sediments and rocks have been stripped away by higher sea level stands in the past. Essentially it’s the Saint Marks Limestone and the Suwannee Limestone outcrop in this area, both in Leon County, Wakulla County and Jefferson County.
We see a map of the formations below. This is a map of the geology beneath us in Florida. Something to keep in mind is that, while the map is flat, the formations overlap each other in three dimensions. The caves, tunnels, and other conduits carrying water through the aquifer likewise travel in three dimensions.
Under the hood: geology of the Woodville Karst Plain
Chris is referring to geologic formations that were deposited at different times in Florida’s ancient past. Between 160-23 million years ago, most Florida was beneath a shallow ocean. For over 130 million years, this ocean was full of life: corals, snails, bivalves, sea urchins, and plankton, to name a few. These animals have exoskeletons made of calcium carbonates, and over geologic time, as they lived and died, the calcium carbonate in their exoskeletons accumulated and created limestone rock.
Around 28 million years ago, the climate cooled and sea level fell, exposing parts of the Florida Platform. Sediments carried by Georgia rivers were deposited over the limestone formations. Porous limestone rock stores water – it makes our Floridan Aquifer system.
Each of the formations depicted in the geologic map above were deposited during a different geologic time period. Suwannee limestone was deposited during the early Oligocene Epoch (33.9 – 28.8 million years ago). The St. Marks Formation is a combination of limestone and dolostone (another carbonate rock also found in Suwannee Limestone). It was deposited between 20-23 million years ago, during the early Miocene.
The Hawthorn Group is made of multiple formations that in southeast Georgia and northeast Florida. Locally, this includes the Torreya Formation, to the north of the Cody Escarpment and the Woodville Karst Plain, west to the Apalachicola River. It was deposited later in the Miocene Epoch than the St. Marks Formation, between 15 and 19 million years ago. The upper parts of the Torreya Formation are made of sand, silt, and clay, with limestone below it.
On the Surface: The Red Hills flatten to the Woodville Karst Plain
Chris Werner: Most people will notice that when they drive south out of Tallahassee, and they go down this really big hill called the Cody Escarpment. And that essentially is where the Hawthorn kind of disappears. Then you’re essentially driving on unconsolidated sands and clays from, basically, beach or dune type structures that are remnant of those past sea level stands.
Looking at both of the maps above, we can see the Torreya Formation is higher and hillier than the Woodville Karst Plain. Hawthorn Group formations represent the first above-water portions of Florida, such as the Lake Wales Ridge, the Tallahassee (or Red) Hills, and the Apalachicola Bluffs and Ravines. In the panhandle, the Cody Escarpment is an ancient coastline where the Hawthorn Group thins out, and the land flattens.
Any regular WFSU Ecology Blog reader has likely noticed how often I visit sandhill habitats. These were once beach dunes on this coastline.
An ideal geology for large springs and caves
North of the Cody Escarpment, the limestone aquifer is protected by a layer of rock and sediment. On the Woodville Karst Plain, the limestone is near the surface, creating conditions where springs and sinks can form.
Chris Werner: The term karst, basically, is a geologic term that we use that describes when limestone is exposed at the surface, or it has very thin sediments above it.
Usually rainwater is slightly acidic. So what happens is when it rains, that permeates through those sands and clays, they’re still kind of charged a little bit with carbon dioxide. And they slowly dissolve out the limestone. What happens is you form all these voids within there. [You] still get flow of the water.
Chris Werner: In this area, which is somewhat unique, you’ve got five huge first-magnitude springs. You’ve got underground rivers, for the most part, that feed those. And then you’ve got swallets.
You’ve got surface streams, particularly in the Hawthorn Formation up around Tallahassee and to the west and the east a little bit, and as soon as they get to the Woodville Karst Plain, they usually sink into the ground, and those form parts of those underground conduits.
Chris Werner: So, most of the flow [in the Woodville Karst Plain] is not via surface streams. Most of the flow is captured underground, and so your drainage basin is essentially subterranean at that point.
Water in limestone: contained in the smallest pores, and in the largest caves
Rob Diaz de Villegas: And so you have water flowing in caves, but it’s also kind of stored in the rock itself, right? It’s a porous rock.
Chris Werner: That’s right. The limestones are very, very porous. And they’re very permeable as well. That’s basically our drinking water… It’s the upper Floridan aquifer, to be exact, in this area. And it provides most of the drinking resources for Leon County, City of Tallahassee, Jefferson County, Gadsden County, Wakulla County, you name it.
Chris Werner: Everybody’s getting their water from the upper Florida Aquifer. And that’s the potable part of the aquifer. The aquifer is actually much, much deeper. Unfortunately, you can’t drink [water from the lower aquifer] because it’s non-potable. That deeper part of the aquifer has really high total dissolved solids. And it’s probably more influenced by sea level. You get… kind of brackish, and salt water, high chloride, high sodium, high dissolved solid type of waters.
Cave exploring is only part of the equation
The water we drink, and that flows out of springs, moves through the aquifer in the smallest cracks and passages, and also through caves wide enough to “fly a jumbo jet through.” The cave system is the largest of its kind in North America, stretching over twenty five miles. Chris says this is the darkest place on earth, and when they enter a new cave, it is the first time light has ever illuminated it. It’s also the first time humans have laid eyes on this alien environment.
Exploring the cave is the exciting part. It’s the part we can see, and what we see is unlike anything we’ve seen before. But it’s only a part of the equation. In our other post for this episode of Coast to Canopy, we talk about the research of the Woodville Karst Plain Project. What they can’t explore physically, they will connect using chemistry and hydrology. Like I said in the intro, this endeavor is a mixture of discovery and hard science. Each informs the other, and makes the upper aquifer in our area slightly less mysterious.
November 13, 2025- Edits were made to the section on geologic formations, with guidance from the Florida Geological Survey.
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