Director's Message

Welcome to the July 2025 edition of the Florida Geological Survey (FGS) News and Research. The FGS just celebrated its 118^th birthday!  As one of the oldest continuously functioning state agencies, we consistently provide geoscience information to keep our citizens safe, our economy strong and our natural resources protected. We take great pride in what we do at the FGS. I am pleased to share with you some of our ongoing work and other newsworthy events.

We recently provided geological and paleontological specimens which are now on display outside the office of the Florida Department of Environmental Protection's (DEP) Secretary Alexis A. Lambert. These specimens showcase some of Florida’s unique geology and paleontology and allow visitors to our agency an opportunity to learn about the FGS. In February, I had the opportunity to represent the FGS in Washington, D.C., during the Association of American State Geologists’ Spring Liaison meeting. Additionally, several FGS geologists attended conferences to present their research and further multi-state collaborations. The FGS uses activities like these to communicate the important role geoscience plays in our society.

In this issue of the FGS News and Research, we focus on the geology of the western portion of the Florida Panhandle. This region, known geomorphically as the Southern Pine Hills District, is characterized by stream systems developed in the sands and clays of the Citronelle Formation. It is home to Florida’s highest elevation. At 345 feet above sea level, Britton Hill is the lowest high point of any U.S. state. There are several Outstanding Florida Waters (OFWs) in this portion of the state designated for their pristine condition. Blackwater River State Park provides an excellent opportunity to explore the tea-colored Blackwater River, one of the OFWs in this area. The Southern Pine Hills District doesn’t have many karst features described in our previous newsletter, because limestone and dolostone strata do not occur near the land surface. Instead, the surficial geologic formations in the western Florida Panhandle contain mineable quartz sand and clay. Weathered from the Southern Appalachian Mountains and transported downstream by rivers, this sediment was deposited as the Citronelle Formation.

As we consider the geological resources in our state, it is useful to understand how they formed. A Brief Geologic History of Florida describes the processes that shaped our state and contains a link to a more in-depth video, “Rocks, Water, Life: Florida’s Geology.” In this video, several FGS geologists discuss the next State Geological Site, to be designated this fall. Florida Museum of Natural History paleontologist Roger Portell is also featured in the video, describing some Florida fossils. In this newsletter, he explains how his recent research on fossil echinoderms led to a change in the name of Florida’s unofficial state fossil, the sea biscuit Eupatagus mooreanus.

In the final article of our three-part series discussing Quaternary undifferentiated sediments in Florida, we explore our state’s largest economic deposit of heavy mineral sands. Trail Ridge sands, our Featured Formation, is an informal lithostratigraphic unit occurring in northeast Florida. The heavy mineral sands that occur in this unit are primarily mined for their titanium content. They are also being assessed as a potential mineable source of rare earth elements that are considered by the U.S. Geological Survey (USGS) to be critical minerals necessary to produce technology used in the communication and defense industries. Through geological mapping and characterization of the Trail Ridge sands, the FGS increases our understanding of Florida’s valuable geological resources.

Stay tuned for information about our open house this October and the dedication of our ninth State Geological Site. Thank you for your continued support of our organization.

Sincerely,

Guy H. Means

Director and State Geologist
Florida Geological Survey
Florida Department of Environmental Protection

In this issue...

• Director's Message
• FGS News
• Earth Systems of the Western Panhandle: The Southern Pine Hills District
• Geology in...the Real Florida: The Geology of Blackwater River State Park
• GEOFACT: Origin, Mining and Uses of the Panhandle Sands
• A Brief Geologic History of Florida
• Reinstated Name for Florida’s Unofficial State Fossil
• Featured Formation: Quaternary Undifferentiated Sediments and other Undifferentiated Quaternary Units in Florida, Part III
• See Previous Editions

FGS News

Florida Geology on Display The FGS provided specimens to highlight Florida’s unique geology and paleontology, which are on display outside the office of DEP Secretary Alexis A. Lambert. The exhibit will enable visitors to learn about Florida’s geology when meeting with the Secretary and other DEP Leadership. Included in the collection, located in the Marjory Stoneman Douglas Building in Tallahassee, are Florida’s state stone (agatized coral), state gemstone (moonstone) and unofficial state fossil (Eupatagus mooreanus). A dugong rib and megalodon shark tooth are also showcased, as well as several impressive specimens of crystalline calcite. We also provided examples of rocks that host some of Florida’s aquifers (limestone) and confining units (anhydrite) and a sample of the Sunniland Formation, an oil-bearing carbonate rock (limestone or dolostone) from 13,260 feet below land surface in southwest Florida. Figure 1. DEP Secretary Alexis A. Lambert and FGS Director and State Geologist Harley Means in front of the display highlighting Florida geology.

FGS Represented at the Association of American State Geologists’ Spring Liaison

FGS Director and State Geologist Harley Means, along with 19 other State Geologists, attended the Association of American State Geologists' (AASG) Spring Liaison in Washington, D.C., this February. During the weeklong event, State Geologists engaged with members of Congress and representatives from federal and non-governmental agencies to provide information about how State Geological Surveys (SGSs) play an essential role in the advancement of geological knowledge that is critical to our nation’s economic welfare and national security.  The group advocates for the continuation of funding, passed from Congress through federal agencies to SGSs.  The federal funding through these programs is usually matched one-to-one by SGSs. These collaboratively funded projects provide critical geological information about energy resources, critical minerals and geologic hazards.

New Study Released on the Value of Geological Mapping to Society

This spring the American Geosciences Institute (AGI) published the Economic Analysis of the Costs and Benefits of Geological Mapping in the United States of America for the Period from 1994 to 2019. Geological maps, published by SGSs and the USGS, are freely available for use by the public and private sectors, academia and governmental agencies. Researchers compiled a value and return on investment analysis for mapping projects completed from 1994-2019. They report that the return on investment for geological mapping is at least 7-10 times the production cost and may be 23-35 times the production cost. The study was funded by the USGS and directed by the Nevada Bureau of Mines and Geology. Multiple academic institutions assisted with analytical research and 24 SGSs provided data, support and feedback.

The FGS contributes to these valuable mapping efforts through the Florida Geological Survey Mapping Initiative (FGSMI), which combines efforts from our FLAGMAP, STATEMAP and Earth MRI programs in order to update the statewide surficial geologic map of Florida. Our longest-running ongoing mapping program, STATEMAP, was established in 1994 with an award of $30,000 from the USGS. Since then, the program has become one of the leading programs of its kind in the U.S., and has been awarded funding annually to continue mapping efforts.

Figure 2. Explore the FGS STATEMAP program and map publications here. 

3D Scans of FGS Fossils

Last spring the FGS collaborated with Florida State University (FSU) researchers to image FGS fossils using Artec 3D scanners. These 3D images have recently been incorporated into the FSU Institutional Repository and can now be viewed as the Florida Geological Survey collection. This publicly available digital collection provides access for detailed 3D examination of Florida fossils. These models can be downloaded and used with 3D printing software to print physical copies of Florida fossils anywhere.

Figure 3. Examine FGS fossils in 3D with the newly released Florida Geological Survey collection, housed in FSU’s Institutional Repository. 

FGS Attends the Southeastern Section Meeting of the Geological Society of America

FGS geologists presented ongoing research at the Geological Society of America’s 74^th Annual Meeting of the Southeastern Section in Harrisonburg, Virginia. The sectional meetings provide an opportunity to receive training, participate in field trips and short courses, discuss ongoing projects and funding opportunities and explore geo-hot topics with our colleagues at various state, federal and academic institutions. To see our submissions and learn more about some of our ongoing projects see the links below.

1. Davis, Benjamin, Lupo, Mary, McMahan, Ericka and Fowler III, Gary, 2025, Investigating Tertiary-Quaternary stratigraphic relationships across Northern Florida: An examination of surficial geology and stratigraphic correlation issues, Geological Society of America, Abstracts with Programs, Vol. 57, No. 2. doi: 10.1130/abs/2025SE-408938
2. Fowler III, Gary, and Davis, Benjamin, 2025, Rare earth element abundances in Florida phosphate mining waste, Geological Society of America, Abstracts with Programs, Vol. 57, No. 2. doi: 10.1130/abs/2025SE-408651
3. Lupo, Mary E., 2025, Revisiting Florida’s deeper stratigraphy and 3D geologic framework, Geological Society of America, Abstracts with Programs, Vol. 57, No. 2. doi: 10.1130/abs/2025SE-408381

Figure 4. Dr. Mary Beth Lupo with her daughter, Madeline, in front of her poster presentation.

FGS Outreach Events

The FGS provided mentors and volunteers for the 2025 Women and Girls in Science, Technology, Engineering and Mathematics (STEM) Event, held at the Challenger Learning Center in February.  About 150 girls in Florida’s Big Bend region attended the event. It was hosted by Florida State University (FSU) in collaboration with Florida A&M University (FAMU) and Tallahassee State College (TSC). The theme was “InnovateHER: Celebrating Women and Girls Who Change the World.”

Figure 5. 2025 Women and Girls in STEM Event. Top left: Crystal Hebets spoke with students about how the FGS uses Geographic Information Systems (GIS) as a tool for mapping and data analysis. Top right: Brittany Duffey (left) and Blakely Webb (right) shared Florida fossils and rocks with students. Bottom: At the end of the mentoring and tabling events, girls enjoyed an IMAX movie with lunch.

In collaboration with the University of Florida Institute of Food and Agricultural Sciences (UF/IFAS) Florida Youth Naturalist Program, the FGS led middle and elementary students on a hike of the Leon Sinks.

The FGS continues to provide virtual museum tours to classrooms around the state, including those working with the Scientist in Every Florida School Program. This program, within the UF Thompson Earth Systems Institute, partners scientists with K-12 public schools in Florida to bridge the gap between scientific research and education.

Students from FSU Department of Earth, Ocean and Atmospheric Sciences visited the FGS. In February, students in the History of Earth Systems course received an FGS museum tour, learned about the geological history of Florida and explored career opportunities. In April, Dr. Ming Ye’s Principles of Hydrology students spoke with State Geologist Harley Means about FGS research, observed drilling and core recovery, learned about tracking water levels in the Upper Floridan aquifer and visited the Florida Geologic Sample Collections Facility.

Figure 6. Dr. Benjamin Davis and Ericka McMahan describe and demonstrate drilling procedures for Dr. Ming Ye’s students.

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Earth Systems of the Western Panhandle: The Southern Pine Hills District

This article is the second in a multi-part series exploring Florida’s geology and the overlying ecology. The focus of the last newsletter was Florida’s Eastern Panhandle-Big Bend Region, as designated in the poster, “Earth Systems: The Foundation of Florida’s Ecosystems,” by Ed Lane and Frank Rupert. The regions described in the poster often correspond well with the districts and provinces defined in the more recently released Florida Geomorphology Atlas. The focus of this newsletter is the western Florida Panhandle, which corresponds to the Southern Pine Hills District. According to the Florida Geomorphology Atlas this area “includes all of Escambia, Santa Rosa, and Okaloosa counties. It continues eastward into most of Walton, and small parts of western Washington, Holmes, and Bay counties” (p.14).

Figure 1 displays the geology, surface features and vegetation representative of the western Panhandle. Figure 1 and the and quoted text below are original, as published in the 1996 poster, “Earth Systems: The Foundation of Florida’s Ecosystems,” with the exception of updated geomorphic nomenclature. Figure 2, all links, footnotes and text in bold are additions, relating the original text to updated information in the Florida Geomorphology Atlas, or providing further information about the geology and surface features of the area.

Figure 1. Geology, surface features and vegetation representative of the western Panhandle, now referred to as the Southern Pine Hills District.

“The western Florida panhandle is underlain by thick Miocene to Recent sands and clays. Carbonates, which are common at shallow depth elsewhere in Florida, generally lie at depths in excess of 400 feet below land surface. Clays in the thick overburden sediments shield this limestone from extensive dissolution. As a result, karst features, such as sinkholes, are rare to absent in the four counties of the western panhandle. The thick sands and gravelly sands also form the primary drinking water aquifer, which due to its lithology, is named the sand-and-gravel aquifer¹.

Extending approximately 50 miles from the Alabama border on the north to the Gulf shoreline, the region is divided into two major geomorphic zones, now referred to as provinces. Skirting the northern edge of the western panhandle is a broad, stream-­dissected upland named the Western Highlands, now referred to as the Western Highlands Province². South of these highlands is a generally flat and elevationally lower zone named the Gulf Coastal Lowlands, now referred to as the Panhandle Coastal Lowlands Province³. 

The Western Highlands Province consists of clayey-sand hills, which attain elevations up to 345 feet above sea level (ASL)⁴. Surface water features consist primarily of deeply-incised streams. Plio-Pleistocene clayey, gravelly, quartz sands of the Citronelle Formation form the core of the hills. Blanketing the Western Highlands Province is a relict, variably thick veneer of marine terrace sands, deposited by high-standing Pliocene and Pleistocene seas. Local ecosystems are controlled largely by the topography and by the lithology and hydrology of the underlying geologic formations. Limonite⁵ hardpan and clay beds, for example, commonly retard downward percolation in many areas, causing high standing water tables.

Sandy soils derived from the Citronelle Formation and the undifferentiated terrace sands, which have been leached of any contained clay, provide dry, well-drained (xeric) conditions, particularly on hill tops and slopes. Such areas typically support upland sandhill or pine forest ecosystems consisting primarily of longleaf pine (Pinus palustris)⁶, once the principal upland tree species in prehistoric times, along with other pine species, oaks, wiregrasses, herbs, and low woody shrubs.

Interspersed with the sandhill ecosystem on the rolling topography of the Western Highlands Province, particularly along the smaller stream courses, are upland hardwood forests and upland mixed forests. Clayey, organic, sandy soils, developed from the shallow-lying Alum Bluff Group (described on page 14 of the Southeastern Geological Society Guidebook 51) and Citronelle Formation, retain more moisture than the deep sand regions and support a decidedly mesic (moist) community. In these regions the common flora includes magnolia, oak, hickory, beech, and various pine species. Bottomland hardwood forests and floodplain forests are developed along the major alluvial stream courses⁷ of the region, where higher water tables and high soil clay and organic content provide mesic conditions. Moisture dependent forests of water and live oak, sweetgum, magnolia, beech, palmetto and river birch extend along the upper reaches of the Escambia River Valley⁸. Freshwater tidal swamp⁹ occupies the lower, seaward portion of the valley. The southern boundary of the Western Highlands Province is marked by a relict marine escarpment¹⁰ which forms a topographic break between the elevationally higher uplands to the north and the lower, generally flat Panhandle Coastal Lowlands Province to the south.

Figure 2. The Southern Pine Hills District, as defined by the Florida Geomorphology Atlas, is highlighted in dark yellow. Major rivers in this district include the Perdido, Escambia, Blackwater, Yellow, Shoal and East Bay, as well as the lower portion of the Choctawhatchee. The black line delineates the watershed for these rivers, which can also be seen in the insert, top left. For most major rivers in this region, the headwaters originate in southern Alabama. The underlying land surface elevations, imaged by LiDAR, display how topography contributes to the largely dendritic patterns of these drainage systems. Britton Hill, indicated with a yellow star, is the highest point in Florida at 345 feet above sea level.

The Panhandle Coastal Lowlands Province comprises a sandy, gently-seaward sloping plain extending from the southern edge of the Western Highlands Province south to the Gulf of Mexico, now called the Gulf of America¹¹. Elevations rise from sea level at the Gulf coast to about 50 feet ASL at the toe of the Western Highlands Province. The Panhandle Coastal Lowlands Province is characterized by numerous relict sand beach ridges, dunes and swales formed by high-standing Pleistocene seas. This sandy topography is underlain by generally clean quartz sands, creating moderate to poorly-drained mesic conditions. Pine flatwoods occupy much of the inland portions of the lowlands. Near the coast, maritime hammock flora of live oak, cabbage palm, and red bay occur in discontinuous forests, rooted in the thick quartz sands of old coastal dunes. Well developed dunes along the modern coast¹² support a beach dune ecosystem including sea oats, cordgrass, sand spur, and morning glory. Behind the dunes, especially on the barrier islands, is a coastal grassland ecosystem. This flat, treeless ecosystem is developed on clean sands and typically supports only grasses, prostrate vines and other maritime herbaceous flora.”

Footnotes

1. Described in the Ground Water Atlas of the United States: Alabama, Florida, Georgia, South Carolina, HA 730-G, by the U.S. Geological Survey (USGS), this aquifer extends from Mississippi, across Alabama, and into the westernmost counties of Florida. The sediments that form the aquifer were transported by streams from their original source rocks in the Appalachian Mountains and deposited in a delta environment. Deposition began in the middle Miocene. For more information about the aquifers of Florida, see FGS Special Publication 28.
2. In the Florida Geomorphology Atlas, the FGS refined the mapping of geomorphic districts and their provinces. This area is referred to as the Western Highlands Province. Please see the Atlas for more information about districts and their provinces.
3. Now referred to as the Panhandle Coastal Lowlands Province. The Panhandle Coastal Lowlands Province and the Western Highlands Province make up the Southern Pine Hills District.
4. The highest elevation in Florida is Britton Hill in northern Walton County, seen in Figure 2. At 345 feet ASL, it is the lowest high elevation of any state in the U.S. Currently, elevations are often measured using satellites or another airborne sources and reported digitally, as with the USGS National Geospatial Program (NGP). LiDAR, or Light Detection and Ranging, is one technology used to measure elevations today. The FGS applies LiDAR measurements in many projects, including to identify sinkholes, locate small springs and establish topographic base maps for creating geologic cross sections. The map of drainage basins shown in Figure 2 is underlain by topographic imagery created using LiDAR data. Elevations can also be physically measured from sea level or from benchmarks placed by previous surveyors. Before airborne measurements, these physical measurements were the only way scientists had to measure elevation. Scientists shared these measured elevations in historic documents like FGS Bulletin 32. To learn about historic tools and methods used to measure the elevations of the land surface, explore the History of the Topographic Branch (Division) of the USGS.
5. Limonite is a hydrated iron oxide. It is formed by the weathering and oxidizing of iron minerals, and thus is typically a rust color. Limonite can cement sediments together, making a hard layer, called hardpan. These hard layers are resistant to erosion and restrict groundwater flow. Limonite nodules are common in the Citronelle Formation. FGS Special Publication 8R, Guide to Rocks and Minerals of Florida, contains information about limonite on pages 34 and 35.
6. The longleaf pine/wiregrass ecosystem once covered much of the Atlantic and Gulf Coastal Plain. Due to harvesting and land-use changes, this ecosystem now occupies only a few percent of its original areal extent. To research and preserve this habitat, the Florida Forest Service and the Florida Natural Areas Inventory created the Longleaf Pine Ecosystem Geodatabase (LPEGDB). With their Florida Longleaf Pine Map Viewer, observe the modern extent of these pine ecosystems. Learn about some of the species that inhabit longleaf pine ecosystems, including diamond back rattlesnakes, in this WFSU blog and video.
7. Due to the high clay content in parts of the Citronelle Formation, rainfall often results in runoff, creating streams. Rivers in this region, displayed in Figure 2, include the Perdido, Escambia, Blackwater, Yellow, Shoal and East Bay, as well as the lower portion of the Choctawhatchee. Most of these rivers have headwaters in Alabama, as seen in the inset of Figure 2. See the Florida Geomorphology Atlas for more information about these watersheds. East Bay/Blackwater Bay/Lower Yellow River Preliminary Baseline Resource Characterization provides an overview of the Pensacola Bay System. Explore the geology of the Blackwater River State Park in this newsletter.
8. The Conecuh River in southern Alabama joins Escambia Creek near the Florida-Alabama border to form the Escambia River, which flows into Escambia Bay. To learn more about this watershed, read FGS Bulletin 46 and Report of Investigations 40, historic publications on the geology and the water resources of Escambia and Santa Rosa Counties.
9. Tidal swamps are often flooded with saltwater, and therefore include salt-tolerant plant species. Occasionally inland freshwater swamps are located near coastlines. Their water levels can be affected by tides when river or groundwater levels are pushed up by high tide, though the water in the swamp stays predominantly fresh, not salty. Learn more about Florida wetlands through the Florida Wetlands Extension Program and in the Florida Natural Areas Inventory.
10. Shorelines have changed many times in Florida’s geologic history for a variety of reasons. View Terraces and Shorelines of Florida as reported in FGS Map Series No. 71 to explore further.
11. Per Executive Order 14172 this body of water is now referred to as the Gulf of America.
12. Dunes at Grayton Beach State Park contain coastal dune lakes. These rare, permanent lakes are located near coastlines and are intermittently linked to the ocean.

Additional Resources

Florida Natural Areas Inventory (FNAI), 2010, Guide to the natural communities of Florida: 2010 edition: Tallahassee, Florida Natural Areas Inventory, 279 p. https://www.fnai.org/PDFs/Full_FNAI-Natural-Community-Classification-Guide-2010_20150218.pdf.

Knight G.R., Oetting J., and Cross L., eds., 2011, Atlas of Florida's Natural Heritage: Biodiversity, Landscapes, Stewardship, and Opportunities: Tallahassee, Florida, Institute of Science and Public Affairs, Florida State University, 162 p.

Scott, T.M., 2001, Text to accompany the Geologic Map of Florida: Florida Geological Survey Open-File Report 80, 29 p., https://doi.org/10.35256/OFR80.

Scott, T.M., Campbell, K.M., Rupert, F.R., Arthur, J.D., Green, R.C., Means, G.H., Missimer, T.M., Lloyd, J.M., Yon, J.W., and Duncan, J.G., 2001, Geologic Map of the State of Florida: Florida Geological Survey Map Series 146, scale 1:750,000, https://doi.org/10.35256/MS146.

Southeastern Geological Society Ad Hoc Committee on Florida Hydrostratigraphic Unit Definition, 1986, Hydrogeological Units of Florida: Florida Geological Survey Special Publication 28, 8 p., https://doi.org/10.35256/SP28.

Whitney, E.N., Means, D.B., Rudloe, A., and Jadaszewski, E. (Illustrator), 2014, Florida's Uplands: Sarasota, Florida, Pineapple Press, 166 p.

Whitney, E.N., Means, D.B., and Rudloe, A., 2014, Florida's Waters: Sarasota, Florida, Pineapple Press, 142 p.

Whitney, E.N., Means, D.B., Rudloe, A., and Jadaszewski, E. (Illustrator), 2014, Florida's Wetlands: Sarasota, Florida, Pineapple Press, 166 p.

Williams, C.P., Scott, T.M., and Upchurch, S.B., 2022, Florida Geomorphology Atlas: Florida Geological Survey Special Publication 59, 238 p., https://doi.org/10.35256/SP59.

Please use the Online FGS Publication Search to explore the geology of individual counties or geologic units within this area.

Contact: Mabry Gaboardi Calhoun, Ph.D.

Suggested citation for poster: Lane, E., and Rupert, F.R., 1996, Earth Systems: The Foundation of Florida’s Ecosystems: Florida Geological Survey Poster 6, Color, 40” x 60”, https://doi.org/10.35256/P06.

Link for this article: https://content.govdelivery.com/accounts/FLDEP/bulletins/3e9bf47#link_1.

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Geology in...the Real Florida: The Geology of Blackwater River State Park

Blackwater River State Park is located in the Florida Panhandle adjacent to the Blackwater Wildlife Management Area and the Blackwater River State Forest. Situated in Santa Rosa County, the park provides many recreational opportunities along the white, sandy banks of the Blackwater River. With stands of longleaf pine, magnolia and Atlantic white cedar, this state park provides the perfect backdrop for a real Florida experience. Activities offered at the park include hiking, cycling, birding, fishing, paddling and swimming. Explore paddling opportunities on the Blackwater River in this interactive Blackwater River Canoe Trail photo tour.

Figure 1. An exposure of the Citronelle Formation on the Blackwater River in Santa Rosa County is shown in this historic FGS photograph from 1979. Former State Geologist Walt Schmidt is in the stern and Mike Knapp is in the bow of the boat for this geological expedition. White sand bars highlight the clean, tea-colored water.

The geomorphology of the Blackwater River State Park is representative of  the Western Highlands Province of the Southern Pine Hills District (Williams et al., 2022) in which it resides. Elevations range from 25 feet above sea level (ASL) within the streambed to 150 feet ASL in the southwestern corner of the park. The river is named for its tea-colored water, which shows up clearly against its white sand bars (Figure 1). This color is derived from tannins in leaf litter. When runoff flows over vegetation, it picks up these natural organic compounds and carries them to the stream. Tannins are dark in color and naturally slightly acidic. As with brewed tea, the darker water color does not indicate pollution. The Blackwater River is an Outstanding Florida Water, one of the most pristine water bodies in the Florida Panhandle. Headwaters of the Blackwater River originate in the Conecuh National Forest in Alabama. The sand-and-gravel aquifer provides the majority of water to this river system, with surface runoff providing the rest (Lewis, 2010). 

Geology of Blackwater River State Park

The Blackwater River State Park sits on top of Quaternary Alluvium (Qal), mapped in the Blackwater River valley (Figure 2). These sediments were likely deposited during the Pleistocene or Holocene epochs and are restricted to river basins. They are primarily comprised of clays, sands and gravels eroded from upland Citronelle Formation (Tci; Figures 1 and 2).

 Figure 2. Surficial geologic map of the area surrounding Blackwater River State Park.

Surrounding the Blackwater River floodplain is the Citronelle Formation, deposited in the late Pliocene or early Pleistocene epoch. It consists of sands and gravels with varying amounts of clay. Within the southern portion of the U.S. Geological Survey Crestview 30 x 60 minute quadrangle, the Citronelle Formation is variable in thickness, ranging from only a few feet to over 300 feet (Green et al., 2001). Due to the variable lithology, both vertically and horizontally, determining the depositional environment of this formation becomes complex. The occurrence of marine fossils in portions of this formation clearly suggests deposition in a near-shore marine environment (Figure 3, left). Other features of this formation, such as cut-and-fill structures and massive cross-bedding, suggest a fluvial environment (Figure 3, right). The deposition of the Citronelle Formation has been influenced by both near-shore marine and fluvial depositional processes, possibly being deposited in numerous coalescing deltas (Means, 2009).

Figure 3. Left: Ophiomorpha nodosa, a trace fossil thought to be a Callionassid shrimp burrow, indicates near-shore marine deposition of this portion of the Citronelle Formation. Right: Cross-bedding in the Citronelle Formation suggests fluvial deposition of these sediments.

In this region, the Citronelle Formation unconformably overlies Miocene formations of the Alum Bluff Group (Green et al., 2001). Sediments of the Alum Bluff Group range from clayey sands and gravels to greenish, stiff, micaceous clays with variable admixtures of silt, sand and shell. This group primarily includes subsurface units; however, they are exposed in creeks and river valleys in parts of Walton, Holmes and Washington Counties (Green et al., 2001; Means, 2009).

The underlying geology of an area strongly influences its surface features. Clay within the Citronelle Formation slows the infiltration and downward percolation of water, and results in more surface runoff. Runoff can lead to rivers. The Blackwater River is one of several rivers developed in the Southern Pine Hills District due to the high clay content of the underlying sediments. To learn more about the connection between the geology and surface features in this area, explore Earth Systems of the Western Panhandle: The Southern Pine Hills District.

References Cited

Green, R.C., Means, G.H., Scott. T.M., Gaboardi, M.M., Evans, W.L., III, Paul, D.T., and Campbell, K.M., 2001, Surficial and Bedrock Geology of the Southern Portion of the U.S.G.S. 1:100,000 Scale Crestview Quadrangle, Northwestern Florida: Florida Geological Survey Open-File Map Series 90, 2 pl., https://doi.org/10.35256/OFMS90.

Lewis, F.G., 2010, East Bay/Blackwater Bay/Lower Yellow River Preliminary Baseline Resource Characterization: Northwest Florida Water Management District Water Resources Special Report 2010-02, 101 p., https://nwfwater.com/content/download/5903/40484/EastBayResourceCharacterization.pdf.

Means, G.H., 2009, Marine-influenced siliciclastic unit (Citronelle Formation) in Western Panhandle Florida [Master’s thesis]: Tallahassee, Florida State University, 134 p.

Williams, C.P., Scott, T.M., and Upchurch, S.B., 2022, Florida Geomorphology Atlas: Florida Geological Survey Special Publication 59, 238 p., https://doi.org/10.35256/SP59.

Contact: Ericka McMahan

Suggested Citation

McMahan, E., 2025, Geology in the Real Florida: Blackwater River State Park: FGS News and Research July 2025 edition. https://content.govdelivery.com/accounts/FLDEP/bulletins/3e9bf47#link_6.

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GEOFACT: Origin, Mining and Uses of the Panhandle Sands

The Pliocene-Pleistocene Citronelle Formation (TQci) is the formalized geologic unit at, and near, the land surface in much of the Florida Panhandle. It is comprised primarily of quartz sand and formed by the deposition of fluvial sediments in a deltaic environment. Most of the active mining efforts in this region of the state are focused on the quartz sands and clays of the Citronelle Formation, as shown in Figure 1. According to the Florida Department of Environmental Protection’s (DEP) mines database, there are 15 active sand mining operations in the Florida Panhandle, most of which consist of numerous open pits and borrow areas. The primary uses for the quartz sand, gravel and clay being mined in the Panhandle are for roadway construction, aggregate supply and commercial fill.

Figure 1. FGS Geologists examining pit exposures of Citronelle Formation in Santa Rosa County, Florida.

The Citronelle Formation was named by George C. Matson in 1916 based upon exposures near Citronelle, Alabama. It extends from east Texas across the Florida Panhandle, making it one of the most widespread geologic units in the Gulf Coastal Plain. The Citronelle Formation consists primarily of very fine to coarse quartz sand that contains numerous discontinuous gravel beds, clay stringers and limonitic zones. Although the formation is predominately unfossiliferous it does contain fossilized wood and plant remains, terrestrial vertebrate fragments, mollusks, shark teeth and the trace fossil Ophiomorpha nodosa, which is thought to be a burrow of a Callianassid shrimp. The Citronelle Formation contains varying amounts of accessory muscovite mica, heavy minerals, clay, chert and limonite. The quartz sands of the Citronelle Formation range in color from dark red to yellow-tan to gray. Limonitic “hardpan,” or ferricrete, exposures in the Citronelle Formation are common. Sedimentary structures such as graded bedding and cross-bedding, shown in Figure 2, are pervasive throughout the Citronelle Formation. They are best exposed in pits, quarries and riverbanks, as in Figure 1. The depositional history of the Citronelle Formation reflects a fluvio-deltaic sequence and in its southern extent along the Gulf Coast, represents a transitional environment from bayou to estuarine and marsh (Isphording and Lamb, 1971; Means et al., 2000; Green et al., 2001; Means, 2009). The source of the sediment that comprises the Citronelle Formation is thought to be the Piedmont where fluvial processes eroded and transported the material to the Gulf Coast.

Figure 2. Cross-bedding in the Citronelle Formation, Santa Rosa County, Florida.

The unit is hydrostratigraphically part of the surficial aquifer system and is an important source for groundwater in the Panhandle (Southeastern Geological Society Ad Hoc Committee on Florida Hydrostratigraphic Unit Definition, 1986). In the Citronelle Formation, where clay beds are absent, zones of sand and gravel with high porosity and permeability exist, which are targeted for groundwater extraction and water use. The lithologic character of the Citronelle sediments does not allow for easy differentiation between Citronelle Formation and re-worked Citronelle sediments. The Citronelle Formation is a complex deposit of siliciclastics that exhibits rapid, lateral facies changes and resembles both underlying and overlying formations. Where the Citronelle is not exposed at the surface, it is overlain by Pleistocene terrace deposits composed of reworked sediments from the Citronelle Formation. The late Pliocene-early Pleistocene Citronelle Formation overlays the early Pliocene Jackson Bluff Formation, Miocene siliciclastic sediments from formations in the Alum Bluff Group and the Miocene Pensacola Clay Formation in the western Panhandle of north Florida.

Toward the east, the Citronelle Formation grades laterally into the Pliocene-Pleistocene Miccosukee Formation (TQmc). The Miccosukee Formation, named by Hendry and Yon (1967), is a prodeltaic siliciclastic unit composed of grayish-orange to grayish-red, mottled, poorly- to moderately-indurated, interbedded clay, sand and gravel of variable coarseness and admixtures. The unit is relatively impermeable due to its high clay content and is hydrostratigraphically part of the surficial aquifer system (Southeastern Geological Society Ad Hoc Committee on Florida Hydrostratigraphic Unit Definition, 1986). The Miccosukee Formation has limited distribution in the eastern Panhandle of Florida and occurs from central Gadsden County to eastern Madison County.

A series of undifferentiated Quaternary units is also present in the Panhandle, adjacent to the coastline, as well as to modern Panhandle river systems (Scott et al., 2001). These Quaternary units include the Holocene sediments (Qh), beach ridge and dune sediments (Qbd), alluvium (Qal) and Quaternary undifferentiated sediments (Qu). These informal units consist of unconsolidated quartz sand, silt and clay, and have links to the Panhandle geomorphology (i.e., coastal, riverine, estuarine, etc.). Due to the limited aerial extent and lateral variability of these unconsolidated sediments, they are not targeted for mining purposes.

References Cited

Hendry, C. W., Jr.,  and Yon, J. W., Jr., 1967, Stratigraphy of Upper Miocene Miccosukee Formation, Jefferson and Leon Counties, Florida: American Association of Petroleum Geologists Bulletin 51, no. 2, p. 250-256.

Green, R.C., Means, G.H., Scott, T.M., Gaboardi, M.M., Evans, W.L., III, Paul, D.T., and Campbell, K.M., 2001, Surficial and Bedrock Geology of the Southern Portion of the U.S.G.S. 1:100,000 Scale Crestview Quadrangle, Northwestern Florida: Florida Geological Survey Open-File Map Series 90, 2 pl., https://doi.org/10.35256/OFMS90.

Isphording, W.C., and Lamb, G.M., 1971, Age and origin of the Citronelle Formation in Alabama: Geological Society of America Bulletin 82, no. 3, p. 775-780. https://doi.org/10.1130/0016-7606(1971)82[775:AAOOTC]2.0.CO;2.

Means, G.H., 2009, Marine-influenced siliciclastic unit (Citronelle Formation) in Western Panhandle Florida [Master’s thesis]: Tallahassee, Florida State University, 134 p.

Means, G.H., Green, R.C., Bryan, J.R., Scott, T.M., Campbell, K.M., Gaboardi, M.M., and Robertson, J.D., 2000, Surficial and Bedrock Geology of the Northern Portion of the U.S.G.S. 1:100,000 Scale Crestview Quadrangle, Northwestern Florida: Florida Geological Survey Open-File Map Series 89, 2 pl., https://doi.org/10.35256/OFMS89.

Scott, T.M., Campbell, K.M., Rupert, F.R., Arthur, J.D., Green, R.C., Means, G.H., Missimer, T.M., Lloyd, J.M., Yon, J.W., and Duncan, J.G., 2001, Geologic Map of the State of  Florida: Florida Geological Survey Map Series 146, scale 1:750,000, https://doi.org/10.35256/MS146.

Southeastern Geological Society Ad Hoc Committee on Florida Hydrostratigraphic Unit Definition, 1986, Hydrogeological Units of Florida: Florida Geological Survey Special Publication 28, 8 p., https://doi.org/10.35256/SP28.

Contact:  Benjamin Davis, Ph.D., P.G.

Suggested Citation

Davis, B.L., 2025, GEOFACT: Origin, Mining and Uses of the Panhandle Sands: FGS News and Research July 2025 edition. https://content.govdelivery.com/accounts/FLDEP/bulletins/3e9bf47#link_8.

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A Brief Geologic History of Florida

Have you ever wondered where the sand on the beaches in Florida originates? Why are there rolling hills between Tampa and Orlando? What is the reason shark teeth occur in rocks far from coastlines? Florida’s geologic history provides answers. Our history is one of changing sea levels, and the shape and size of the land mass currently above sea level that we recognize as Florida has been very different in the past.

Plate Tectonics: Forming Florida’s Basement Rocks

The land that we identify as Florida originated as the result of plate tectonics. Deep below Florida’s current land surface we find igneous and metamorphic basement rocks upon which more recent sedimentary rocks were later deposited. We learn about these basement rocks by studying cores drilled to depths of more than 10,000 feet below land surface. These basement rocks formed hundreds of millions of years ago. They were once located on what was to become the African and South American continental plates, which were then part the Laurentian continent. Around 475 million years ago, when trilobites ruled the oceans and early vertebrates were evolving, this Laurentian continent collided with other landmasses to begin to form the supercontinent of Pangea. As a result of this tectonic collision, mountain belts formed, including the Appalachian Mountains. There were likely several collisions lasting until about 250 million years ago, with Florida’s basement rocks located in the interior of the supercontinent of Pangea, far from any coastlines. At this time Earth was experiencing the Permian-Triassic extinction, which killed about 90% of all species on the planet. It was after this extinction that dinosaurs flourished.

Figure 1. Florida’s basement rocks, accessed by drilling deep cores, can be viewed at the FGS’s Florida Geologic Sample Collections Facility. Click the image above to watch “Rocks, Water, Life: Florida’s Geology.”

Carbonate Platform: Evidence of the Ocean

Pangea then began to rift apart, leaving Florida’s basement rocks, originally part of proto-Africa and South America, sutured onto the North American continent. These rifts resulted in the peninsular shape of Florida, as well as the formation of the surrounding ocean basins. As these oceans developed, they bathed the basement rocks in warm, tropical water. Carbonates, including limestone, were deposited under these waters, on top of the basement rocks. Thousands of feet of layered carbonate sediments settled over the basement rocks to form a carbonate platform, with the weight of the successive layers causing the platform to subside, or sink. These carbonates often contain shells, teeth, bones and other fossils that provide a record of the organisms that lived in those oceans. Fossil shark teeth, deposited during the time that the carbonates were forming, remain in the limestone as evidence that the land currently exposed was once under the ocean.

The oldest rocks now exposed on the surface of Florida belong to the Avon Park Formation. This carbonate formation was deposited beneath a shallow sea around 40 million years ago, long after the Cretaceous/Paleogene extinction event, which killed off all dinosaurs except birds. Because dinosaurs went extinct before the Avon Park Formation was deposited, dinosaur fossils are not present in Florida’s shallow carbonate rocks.   

Figure 2. Sea biscuit fossils, commonly found in Florida limestone, provide evidence of Florida’s marine history.  

Shifting Sands: Stories of Change

Over millions of years, sea levels rose and fell for a variety of reasons, including tectonics, changes in global ice volume, changes in ocean temperature and limestone dissolution. Sediments were deposited in successive layers in a variety of environments, including coral reefs, lagoons, beaches, deltas and barrier islands. Carbonate sediments form in warm, clear water, usually marine. Quartz-rich sediment, including pebbles, sand, silt and clay, were carried by streams and currents from upslope, originating in rocks of the Appalachian Mountains. For millions of years a current flowing across northern Florida and southern Georgia, called the Suwannee Current, prevented most siliciclastic sediment from reaching the peninsula. This current lessened about 30 million years ago allowing sediment derived from the Appalachian Mountains to be deposited over Florida’s carbonate platform. Parts of Florida were above sea level. During these last 30 million years, terrestrial animals roamed exposed parts of Florida, leaving fossil remains that now provide one of the world’s richest records of Cenozoic mammalian evolution. Some of the animals preserved include horses, saber-toothed cats, elephants, rhinoceroses, deer and giant sloths.

Figure 3. Terrestrial mammal fossils, such as the saber-toothed cat above, attest to the timing of Florida’s emergence from the ocean.

Florida’s Geomorphology: Karst Development and Beach Building

Carbonate rocks like limestone, once exposed to the atmosphere, are readily dissolved by rainwater, which is naturally slightly acidic. Dissolution, occurring over millions of years, resulted in the karst features apparent in Florida today, including caves, sinkholes, springs and swallets. Our thick platform of porous limestone is geologically young. Because of the combination of abundant rainwater and thick, young limestone, Florida has one of the highest concentrations of springs in the U.S. and one of the most productive aquifer systems in the world.

Siliciclastic sediment carried by streams and currents was deposited over the limestone, sometimes to be topped again by more limestone when sea levels once again rose. Evidence of these changes can be found in Florida’s geologic record, chronicled in the layers of sediment we can observe and drill down through.

Sand that currently makes up Florida’s beaches can be derived from carbonate material, as it is in the Florida Keys, or can be predominantly quartz sand weathered from the Southern Appalachian Mountains. White quartz sand beaches are a distinctive feature of Florida’s current Gulf Coast barrier islands, like St. George Island and Perdido Key. Once the quartz sand is deposited by water on or near these beaches, it is often picked up and carried by wind. Wind-formed, or aeolian, dunes are a characteristic feature of these beach environments. Similar dunes formed between Tampa and Orlando at times of higher sea levels. By studying processes of formation currently happening, we can learn how past geologic deposits and features could have formed.

Rocks, Water, Life: Florida’s Geology

Explore the geologic history of Florida further in this Florida Crossroads video “Rocks, Water, Life: Florida’s Geology.” In this video, you can hear our former and current State Geologists describe Florida’s geologic history. You will see Florida’s basement rocks, housed at our Florida Geologic Sample Collections Facility. The video also highlights important outcrops as our former Assistant State Geologist visits notable geologic features around the state. Watch closely for a preview of our next State Geological Site! 

Additional Resources

Bryan, J.R., Scott, T.M., and Means, G.H., 2008, Roadside Geology of Florida: Missoula, Mountain Press, 376 p.

Hatchett, L., 2000, Geologic History of Florida: Florida Geological Survey Poster 7, Color, 25” x 37”, https://doi.org/10.35256/P07.

Hine, A.C., 2013, Geologic History of Florida: Major Events That Formed the Sunshine State: Gainesville, University Press of Florida, 229 p.

Lane, E., ed., 1994, Florida's Geological History and Geological Resources: Florida Geological Survey Special Publication 35, 76 p., https://doi.org/10.35256/SP35.

Scott, T.M., 1992, A Geological Overview of Florida: Florida Geological Survey Open-File Report 50, 78 p., https://doi.org/10.35256/OFR50.

Contact: Mabry Gaboardi Calhoun, Ph.D.

Suggested Citation

Gaboardi Calhoun, M.M., 2025, A Brief Geologic History of Florida: FGS News and Research July 2025 edition. https://content.govdelivery.com/accounts/FLDEP/bulletins/3e9bf47#link_5.

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Reinstated Name for Florida’s Unofficial State Fossil

The unofficial Florida state fossil is a beautiful, common, Late Eocene, sea biscuit (Figure 1, right). It was originally described as a new Florida species, Eupatagus mooreanus Pilsbry, 1914. In FGS Bulletin 34, Alfred Fischer concurred with this species designation. Eupatagus mooreanus was later compared with the Eupatagus antillarum, a Caribbean sea biscuit species from the Eocene of St. Bartholomew, described by G. Cotteau in 1875 (Figure 1, left). Based on similarities, it was downgraded and included as a subjective junior synonym of E. antillarum in a publication by C.W. Cooke in 1959. For nearly 65 years this taxon has been known by that name. This year, paleontologists conducted the most rigorous review of all known Eocene and Oligocene echinoids in our state, and published the work in the Florida Museum of Natural History’s Bulletin Series, titled “Paleogene Echinoids of Florida.”  Their findings concluded that E. mooreanus is, in fact, a unique species. Major differences between the two species included the following:

• The anterior paired petals of antillarum are nearly straight, whereas those of E. mooreanus are arched anteriorly and diverge from each other at 145°.
• The upper surface of mooreanus is much more heavily tuberculated, with the zigzagging rows of tubercles extending nearly to the ambitus, anteriorly and laterally.

Thus, our unofficial state fossil is once again properly referred to as Eupatagus mooreanus Pilsbry, 1914.

Figure 1. Recently published monograph, “The Paleogene Echinoids of Florida.” The two echinoids on the cover are Eupatagus antillarum (left) and Eupatagus mooreanus (right).

References Cited

Cooke, C.W., 1959, Cenozoic echinoids of eastern United States: U.S. Geological Survey Professional Paper, 321, 106 p., https://doi.org/10.3133/pp321.

Cotteau, G.H., 1875, Description des échinides tertiares des iles St. Barthélemy et Anguilla. P.A.: Norstedt & Söner. 47 p.

Fischer, A.G., 1951, The Echinoid fauna of the Inglis Member, Moodys Branch Formation: Florida Geological Survey Bulletin 34 (2), 112 p., 12 pl., https://doi.org/10.35256/B34P2.

Osborn, A.S., Portell, R.W., and Mooi, R. 2025, Paleogene echinoids of Florida: Bulletin of the Florida Museum of Natural History, v. 61, no. 1, p. 1-314. https://flmnhbulletin.com/index.php/flmnh/article/view/flmnh-vol61-no1-pp1-314/vol61-no1.

Pilsbry, H.A, 1914, Description of a new echinoderm (Eupatagus mooreanus): Proceedings, Academy of Natural Sciences of Philadelphia, v. 66, no. 1, p. 206–207.

Guest Writer: Roger Portell
Invertebrate Paleontology Collection Director
Florida Museum of Natural History, University of Florida

Contact: Roger Portell

Link for this article: https://content.govdelivery.com/accounts/FLDEP/bulletins/3e9bf47#link_3.

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Featured Formation: Quaternary Undifferentiated Sediments and other Undifferentiated Quaternary Units in Florida, Part III

This is the final article in a three-part series discussing Quaternary undifferentiated sediments (Qu) in Florida. Part one of the series provided a general summary of the Quaternary undifferentiated units. Part two focused on the Quaternary beach ridge and dune (Qbd) and the Quaternary alluvium (Qal). This article discusses Trail Ridge sands (Qtr).

Trail Ridge is 1) a feature closely associated with the Okefenokee Swamp, 2) a paleoshoreline feature, 3) a geomorphic province recognized in northeast Florida (Clark and Zisa, 1976; Williams et al., 2022), 4) an informal lithostratigraphic unit indicated on the surficial geologic map of Florida (Scott et al., 2001; Green et al., 2005; Green et al., 2014; Green et al., 2016) and 5) a natural resource containing economically valuable concentrations of heavy mineral sands and potential for rare earth elements (REEs). For the purpose of this article, we will discuss Trail Ridge sands as an informal lithostratigraphic unit. These sands have long been a topic of interest and regional significance as they host the largest mineable deposit to date, by volume and concentration, of heavy mineral sands in the state of Florida. The unit is mapped from the Altamaha River in Wayne County, Georgia, south into Putnam County, Florida. These deposits have been associated with the Wicomico Shoreline, an Early Pleistocene system that developed during a time when sea level was much higher than present (Hails and Hoyt, 1969). Pirkle and Yoho (1970) and Pirkle et al. (1970) defined the “Trail Ridge Sequence” using two drill cores. Force and Rich (1989) sampled the unit and suggested a post-Miocene, pre-latest Pleistocene age using palynology counts and ¹⁴C dates on peat that occurs near the base of a heavy mineral zone.

Sediments in core samples collected along the ridge are characterized based on grain size, shape, sorting, percentage of accessory minerals, color and any preserved sedimentary structures. These sands are poorly consolidated and vary from white, light gray, tan and reddish orange to brown and black. Colors are largely dependent on the amount and type(s) of clay present and the presence of organics and humate. Sand-sized grains range from very fine to coarse, are variably sorted and dominantly consist of quartz. The accessory mineral assemblage consists of a suite of heavy minerals, clay and mica. Cross-bedding, mottling and finer laminations are observable in outcrop and core samples. Heavy minerals are sourced from crystalline rocks exposed in the Piedmont and Blue Ridge belts of the Appalachian Mountains. Streams and rivers transported these minerals from their source to where they were later deposited in river floodplains, deltas, sand bars and shorelines. Secondary transport can occur along coastlines, where heavy minerals are carried by wave action. Trail Ridge’s famous heavy mineral suite reportedly reaches 16% by weight (Force and Rich, 1989), but it is more commonly observed ranging from approximately 3-7% by weight in samples collected along the ridge. The heavy mineral suite consists of leucoxene, zircon, kyanite, staurolite, rutile, amphiboles, pyroxenes and ilmenite (Lupo et al., in review). Relative concentrations of heavy minerals vary slightly within the Trail Ridge deposit and surrounding area, as seen in Figure 1. The heavy mineral sands that occur in the Trail Ridge sands have historically been mined for titanium although they recently were evaluated as a source for REEs. These minerals are significant because of their value as industrial minerals, their economic importance and their potential association with REEs essential to the fields of technology, energy and defense.

It is this author’s opinion, based on the mineral assemblage, occurrence, morphology and stratigraphic position with respect to the surrounding geology and the geographic setting, that these sands may more appropriately be 1) designated as a geomorphic or economic unit or 2) considered equivalent to deposits mapped as the Cypresshead Formation east and south of the ridge. Furthermore, these units should be evaluated with respect to those mapped west of the ridge as undifferentiated sediments (TQu) (Lupo et al., in review). Large scale mapping and detailed stratigraphic analysis, including the characterization of these units using methods such as quantitative mineralogic and granulometric analyses and facies mapping, would further discussions regarding the formalization and classification of surficial sand deposits across the state.

Figure 1. Surficial geologic map of FGS Earth Mapping Resource Initiative Trail Ridge focus area (Lupo et al., in review). The Trail Ridge polygon is overlain for discussion purposes. Quantitative mineralogy samples are plotted with respect to geographic distribution. Associated pie charts demonstrate the results of quantitative mineralogy assessments with respect to the total heavy mineral (THM) content. Only economic heavy minerals (EHM), sub-economic heavy minerals (SEHM) and select non-economic heavy minerals (NEHM) are represented.

References Cited

Clark, W. Z., Jr., and Zisa, A. C., 1976, Physiographic map of Georgia: Georgia Department of Natural Resources, the Geologic and Water Resources Division, scale 1:2,000,000, 1 sheet.

Force, E.R., and Rich, F.J., 1989, Geologic evolution of Trail Ridge eolian heavy-mineral sand and underlying peat, northern Florida: U.S. Geological Survey Report 1499, 16 p., https://doi.org/10.3133/pp1499.

Green, R.C., Evans, W.L., III, Paul, D.T., and Scott, T.M., 2005, Geologic Map of the Eastern Portion of the U.S.G.S.1:100,000 scale Gainesville Quadrangle, Northern Florida: Florida Geological Survey Open-File Map Series 94, scale 1:100,000, 2 pl., https://doi.org/10.35256/OFMS94.

Green, R.C., Williams, C.P., Bambach, P.W., Apolinar, B., Hannon, L.M., and White, K.M., 2016, Geologic map of the U.S.G.S. Jacksonville 30 x 60 minute quadrangle, northeast Florida [3 plates]: Florida Geological Survey Open-File Map Series 108, scale 1:100,000, 3 pl., https://doi.org/10.35256/OFMS108.

Green, R.C., Williams, C.P., Campbell, K.M., Bambach, P.W., Hannon, L.M., Bassett, S.W., Evans, W.L., III, Paul, D.T., and Apolinar, B., 2014, Geologic map of the USGS Saint Augustine 30 x 60 minute quadrangle, northeast Florida: Florida Geological Survey Open-File Map Series 106, scale 1:100,000, 3 pl., https://doi.org/10.35256/OFMS106.

Hails, J. R., and Hoyt, J. H., 1969, The significance and limitations of statistical parameters for distinguishing ancient and modern sedimentary environments of the lower Georgia Coastal Plain: Journal of Sedimentary Research, v. 39, no. 2, p. 559-580, https://doi.org/10.1306/74D71CD0-2B21-11D7-8648000102C1865D.

Lupo, M.E., Davis, B.L., McMahan, E., and Means, G.H., IN REVIEW, Geologic Mapping in the Trail Ridge Placers, Florida Focus Area: Florida Geological Survey, Report of Investigation 123.

Pirkle, E.G., and Yoho, W.H., 1970, The heavy mineral ore body of Trail Ridge, Florida: Economic Geology, v. 65, p. 17-30.

Pirkle, E.C., Yoho, W.H., and Hendry, C.W., Jr., 1970, Ancient Sea Level Stands in Florida: Florida Geological Survey Bulletin 52, 61 p., https://doi.org/10.35256/B52.

Scott, T.M., Campbell, K.M., Rupert, F.R., Arthur, J.D., Green, R.C., Means, G.H., Missimer, T.M., Lloyd, J.M., Yon, J.W., and Duncan, J.G., 2001, Geologic Map of the State of Florida: Florida Geological Survey Map Series 146, scale 1:750,000, https://doi.org/10.35256/MS146.

Williams, C.P., Scott, T.M., and Upchurch, S.B., 2022, Florida Geomorphology Atlas: Florida Geological Survey Special Publication 59, 238 p., https://doi.org/10.35256/SP59.

Contact:  Mary E. Lupo, Ph.D., P.G.

Suggested Citation

Lupo, M.E., 2025, Featured Formation: Quaternary Undifferentiated Sediments and other Undifferentiated Quaternary Units in Florida, Part III: FGS News and Research July 2025 edition. https://content.govdelivery.com/accounts/FLDEP/bulletins/3e9bf47#link_4.

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The Florida Geological Survey (FGS) collects, archives, interprets and distributes geologic information to benefit the environment and Florida’s communities. FGS is committed to continuously increasing the amount and quality of geoscience data and making it available to the public. Collaboration with local, state and federal agency partners ensures a robust and cost-efficient approach to addressing Florida's environmental concerns.

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