DP -002 The St. Johns River System

Water, Sand, and Time — The St. Johns River System

I wanted to understand whether the very different terrain experienced during the race reflected separate environments or simply different expressions of the same ground. Collecting and examining the samples side by side revealed an unexpected continuity: despite their contrasting appearance underfoot, all four originate from the same geological foundation — ancient marine sands repeatedly reorganized by the slow movement of water across the Florida peninsula. The landscape here was not shaped by mountains or tectonic force, but by patience. The St. Johns River, one of the lowest-energy river systems in North America, has gradually reshaped this terrain over millions of years, allowing water rather than elevation to define the land.

St. Johns River Watershed, Florida — The low-energy river system responsible for reshaping much of northeast Florida’s terrain and soil composition over millions of years.

Regional Context

Why the St. Johns River Matters

The St. Johns River is unusual.

• flows north (rare but not unique)

• drops only about 30 feet over ~300 miles

• moves extremely slowly

• frequently spreads laterally instead of cutting downward

Because the gradient is so small:. Water does not carve the land — it rearranges it.

Instead of valleys and rock exposure, the region developed:

• floodplains

• wetlands

• sandy terraces

• pasture flats

• pine flatwoods

The four samples taken sit along this continium.

Deep Time Timeline of Florida

Formation of Florida over deep time — from ancient shallow seas to a water-shaped peninsula built on marine sediments.

Stage 1 — Ancient Sea (Millions of years ago)

Florida was submerged beneath shallow seas which resulted in:

• thick deposits of quartz sand

• marine sediments forming the peninsula’s foundation

Each of hte samples taken begin here.

Stage 2 — Emergence and Drainage Formation

As sea levels fluctuated:

• water retreated and returned repeatedly

• sediments were sorted again and again

• proto-river systems formed

The St. Johns basin became a low basin holding water rather than draining it quickly.

Stage 3 — Slow River Dominance

Unlike mountain rivers, the St. Johns:

• floods outward

• deposits sediment gently

• builds soils slowly

• maintains a high water table

  
  

This creates landscapes controlled by moisture rather than elevation.

Reading Deep Time Through Soil

To underadtand the current relationship of this geological occurrence, soil samples were collected from two main sites: Diamond D Ranch and Sal Taylor Nature Preserve.

Diamond D Ranch

Latitude: 30.1978775°N

Longitude: −81.9326596° W

Sal Taylor Creek Preserve

Latitude: 30.212557° N

Longitude: −81.915281° W

The Four Samples as One System

Qualitative Field Data Collection with Physical Sampling

Soil samples were collected y from exposed trail surfaces, open ground, or shallow subsurface layers after clearing organic debris. Each sample was placed into a labeled sealable bag noting location, environment, and approximate collection context. Samples were transported my home workspace and air-dried overnight to stabilize moisture content and preserve structure. Once dried, small portions were separated and examined under a digital microscope to observe grain size, organic material, coloration, and sediment composition. Photographs were taken directly through the microscope to document microstructure for later comparison across venues and environmental conditions.

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Sample DPS- 006

Spartan Race Mile One — Floodplain Mud

Mile One of the Super/Spring Course

Hydrologic Role - Active water influence

Observed:

• clay/silt binding

• organic saturation

• poor drainage

• cohesive mud

This material formed where floodwater or seasonal saturation allows fine particles to settle.

Because river flow is slow:

• sand drops first

• silt and clay accumulate later

• organic matter mixes in

This is classic overbank deposition tied directly to St. Johns flood dynamics. This soil exists because water lingers.

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Sample DPS-007

Mile Five (near Sandbag Carry) — Pasture Soil Under Tree

Mile 2 of the Sprint Course Near Sandbag Carry

Hydrologic Role: Moderated water influence

Observed:

• sandy matrix

• strong organic development

• stable aggregation

Here water is present but controlled.

The high regional water table provides moisture, but slight elevation prevents flooding.

The result is that:

• vegetation thrives

• organic soil forms

• biology stabilizes sand

This represents land slightly raised above floodplain influence — a natural terrace created by long-term sediment redistribution.

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Sample DPS - 008

Sal Taylor Preserve — Trail Surface

Sal Taylor Creek Preserve Mile .05 Primary Trail

Hydrologic Role: Drainage-dominated surface

Observed:

• clean quartz sand

• minimal fines

• pale coloration

This means that:

• Rainwater rapidly percolates downward through sand.

• Fines are washed away over centuries.

• What remains is nearly pure parent sediment.

• This is the geological baseline exposed when biology or sediment accumulation is minimal.

• Water here removes rather than deposits.

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Sample DPS - 009

Sal Taylor Preserve (4.7 miles from Race Venue) — Subsurface Forest Soil

Sal Taylor Creek Preserve Forest Soil .025 miles from Primary Trail

Hydrologic Role: Biological water regulation

Observed:

• organic coatings

• decomposed litter

• early soil aggregation

• 
  

Interpretation:

• Forest debris slows evaporation and runoff.

• Water cycles locally instead of moving laterally.

• Biology begins rebuilding soil on top of ancient sand.

• This is the landscape attempting to reconstruct stability between flood and drainage extremes.

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Summary and Intepretration

The collected soil samples from the race region and Sal Taylor Preserve reveal variations of a single geological system governed by the St. Johns River basin. Unlike high-gradient rivers that carve valleys, the St. Johns flows slowly across minimal elevation change, redistributing sediment laterally over millennia. Ancient marine sands form the base material across all locations.

Floodplain environments produce fine-grained muds through prolonged saturation, while slightly elevated terraces allow biological soil formation through vegetation cycling. Well-drained flatwoods expose nearly pure quartz sand where water removes finer sediments. Beneath forest litter, organic processes begin rebuilding soil atop this sandy substrate.

These environments represent different hydrologic states rather than separate geological origins. The race terrain therefore reflects not isolated conditions but the long-term interaction between water movement, biological activity, and ancient coastal sediments shaped by the St. Johns River system.

Endnote References

Image Authorship

Florida Geological Timeline illustration, educational infographic generated for explanatory use based on publicly available geological syntheses from the Florida Geological Survey and U.S. Geological Survey (USGS).

U.S. Geological Survey (USGS). St. Johns River Basin Map, Florida. U.S. Department of the Interior, Washington, DC. Public domain.

St. Johns River Water Management District (SJRWMD). Major Watersheds of the St. Johns River Water Management District. Palatka, Florida.

Zettelkasten Sources

All content on this site originates from a Zettelkasten knowledge system. Observations, research, and field notes are stored as linked ideas, and published work emerges as output from that growing archive rather than from isolated writing sessions.

Fl

Florida Platform — Carbonate Bank Growth Under Low Siliciclastic Input Carbonate platform framing for why Florida’s bedrock is limestone-dominant, and what conditions allow thick carbonate accumulation.[1]

Quaternary Sea-Level Cycling — High-Frequency Forcing That Rebuilds Florida and SE Coastal Landscapes Pleistocene sea-level oscillations as the “recent architect” of terraces, paleo-shorelines, barriers, and reorganized coastal drainage.[2]

Florida Rock Inventory — 10 Common Rock Types (Field-Facing List) Practical material-based roster (limestone, dolostone, coquina, marl, sands, clays, chert, etc.) to keep the essay grounded in what’s actually in hand and underfoot.[3]

Florida Basement Inheritance — Gondwanan-Affinity Terranes as the Starting Architecture Deep structural/basement provenance as a long-horizon control on subsidence and the later platform geometry (mostly inferred from cores/geophysics).[4]

Floridan Aquifer Karst — Springs and Sinkholes as Conduit-Flow Expression of Carbonate Bedrock Karst dissolution, conduit permeability, springs, and sinkhole hazards as the modern surface expression of Florida’s carbonate foundation.[5]

Platform Segmentation by Straits/Troughs — Sediment-Routing Valves for Florida Carbonate PersistenceSediment-routing concept: corridors/currents that keep siliciclastics off-platform, enabling long carbonate persistence.[6]

Carbonate Margin / Reef-Front Dynamics — Platform Edges Built by Production + Storm Reworking How platform edges evolve through production, cementation, storms, and sea-level pacing (keep-up/drown/backstep logic).[7]

Carbonate vs Siliciclastic Dominance — Water Clarity and Sediment Supply Decide the Lithologic OutcomeBoundary-conditions note explaining Florida’s carbonate dominance versus clastic-heavy adjacent Coastal Plain sectors.[8]

Dynamic Topography / Regional Warping — Long-Wavelength Vertical Motions on a Passive Margin Gentle tilting/warping as a mechanism for drainage and accommodation changes without obvious local faulting.[9]

Breakup of Pangaea — Triassic–Jurassic Rift Basins and the Atlantic Passive Margin Transition Regional setup note: post-Appalachian rifting and passive-margin subsidence as the stage for Coastal Plain + Florida platform development.[10]

Gulf Salt Tectonics — Jurassic Salt as a Long-Lived Deformation Engine (Indirect SE Control) Offshore salt tectonics shaping margin structure and sediment pathways at regional scale (supporting cast, not the main Florida onshore driver).[11]