The dramatic rock formations at Garden of the Gods in Colorado Springs are sedimentary rock, primarily sandstone and conglomerate belonging to a geological unit called the Fountain Formation. These rocks are roughly 300 million years old, deposited during the Pennsylvanian and Permian periods, and their vivid red-orange color comes from iron oxide coating the sand grains. But the park actually exposes a much wider slice of Earth’s history than most visitors realize, with rock layers spanning from the Cambrian period through the Cretaceous, all tilted nearly vertical by the same tectonic forces that built the modern Rocky Mountains.
The Fountain Formation Up Close
The towering red slabs that define Garden of the Gods belong to the Fountain Formation, a thick package of coarse-grained sedimentary rock laid down during the Pennsylvanian and Permian periods, roughly 320 to 280 million years ago. The formation is not a single uniform rock type. It consists of repeating cycles that grade from gravel and coarse conglomerate at the base of each cycle up through sandstone and into finer siltstone and mudstone at the top.1AAPG Bulletin. Depositional Systems of Fountain Formation and Its Basinal Equivalents, Northwestern Denver Basin, Colorado: ABSTRACT Think of each cycle as a snapshot of a single episode of flooding and settling on an ancient landscape. The coarser material at the bottom represents the most energetic flow, while the fine-grained cap records quieter conditions as the water slowed or dried up.
What makes the Fountain Formation so visually striking at Garden of the Gods is the sheer coarseness of much of the rock. These are not delicate, fine-grained sandstones. Many exposures contain pebbles and cobbles of granite, gneiss, and other crystalline basement rock embedded in a sandy matrix, making them technically conglomerates or arkosic sandstones. Arkosic means the sand is rich in feldspar, a mineral inherited directly from the granitic source rocks that were being eroded at the time. That feldspar content is one reason the rock weathers the way it does, since feldspar breaks down more easily than quartz, contributing to the rough, pitted surfaces you see on many of the formations.
How the Sediments Got There
During the Pennsylvanian and Permian periods, long before the modern Rockies existed, a predecessor mountain range called the Ancestral Rocky Mountains rose across what is now central Colorado. The uplift of one of its major blocks, the Ancestral Front Range, shed enormous volumes of coarse debris eastward and southeastward.2The Mountain Geologist. Detrital Zircon Geochronology of Pennsylvanian-Permian Strata in Colorado: Evidence for Appalachian-Derived Sediment and Implications for the Timing of Ancestral Rocky Mountains Uplift Rivers and flash floods carried boulders, gravel, and sand away from the mountains and spread them across broad, low-lying plains at the mountain front. The Fountain Formation accumulated in this setting.
For decades, geologists described the entire Fountain Formation near Colorado Springs as a product of subaerial alluvial fans, essentially dry-land deposits from braided rivers fanning out at the base of mountains. Farther north in the Denver Basin, the evidence supports exactly that interpretation: stacked fining-upward cycles with cross-bedding, root structures, and soil horizons point to braided-stream and floodplain environments.1AAPG Bulletin. Depositional Systems of Fountain Formation and Its Basinal Equivalents, Northwestern Denver Basin, Colorado: ABSTRACT But the story near Garden of the Gods turned out to be more complicated.
Detailed work on the lower third of the Fountain Formation in the Manitou Springs area, just south of the park, revealed roughly a dozen marine-nonmarine cycles. Each cycle records a sequence that begins with a transgressive lag conglomerate deposited as the sea advanced, followed by offshore mudstone, then progressively shallower-water sandstones with hummocky and planar cross-bedding, and finally a nonmarine conglomeratic sandstone at the top representing the return of dry land and alluvial conditions.3Journal of Paleontology. Trace fossils and marine-nonmarine cyclicity in the Fountain Formation (Pennsylvanian: Morrowan/Atokan) near Manitou Springs, Colorado In other words, the sea repeatedly crept inland across the alluvial plain and then retreated. Only the uppermost part of each cycle is truly alluvial; much of what looks like a monotonous stack of red sandstone actually records pulses of shallow ocean flooding. Trace fossils found in the marine portions confirm this, since the burrowing organisms that made them lived in seawater, not on land.
This distinction matters because it changes what the red rocks are telling you. The lower formations in the park are not simply piles of river gravel. They record a coastline that shifted back and forth across a tectonically active basin, building a complex record of advancing and retreating seas against a backdrop of mountain erosion.
Not Just One Formation
Visitors tend to see Garden of the Gods as a collection of red rock spires and assume it is all the same material. In reality, the park exposes strata ranging from the Cambrian period, over 500 million years ago, all the way through the Cretaceous, roughly 70 to 100 million years ago.4GeoScienceWorld. Garden of the Gods at Colorado Springs: Paleozoic and Mesozoic sedimentation and tectonics Each of these units records a fundamentally different depositional environment, and you can walk across them in the space of a short hike.
The oldest rocks in the park are Cambrian and Ordovician marine sediments, deposited when this part of Colorado sat on a quiet, stable continental interior far from any active mountain-building. These layers are relatively thin and fine-grained compared to what came later. Above them, the thick, coarse red beds of the Fountain Formation and the overlying Lyons Sandstone represent the dramatic shift to a tectonically active setting as the Ancestral Rocky Mountains rose.4GeoScienceWorld. Garden of the Gods at Colorado Springs: Paleozoic and Mesozoic sedimentation and tectonics The Lyons Sandstone, which forms some of the park’s lighter-colored, more smoothly weathered slabs, was deposited under somewhat different conditions, likely in an eolian (wind-blown) to shallow marine setting during the Permian. Its sand grains are better sorted and more rounded than the Fountain Formation’s angular, gravelly texture.
Higher in the sequence, younger Mesozoic rocks record still another world. By the Cretaceous, the Ancestral Rockies had long since eroded away, and a vast shallow sea called the Western Interior Seaway stretched across the continent’s interior. The Cretaceous rocks in the Garden of the Gods area, including shales and limestones, were deposited in and around this seaway as its shoreline shifted with changes in global sea level.5Geological Society of America. Garden of the Gods at Colorado Springs: Paleozoic and Mesozoic sedimentation and tectonics These softer, darker layers are less visually prominent than the red sandstones, but they complete the geological story.
Why the Rocks Stand on Edge
The most visually dramatic thing about Garden of the Gods is not really the rock type itself but the angle at which the beds sit. Layers of sedimentary rock that were originally deposited flat now stand nearly vertical, in some places tilted past 90 degrees and slightly overturned. This did not happen overnight. Two separate mountain-building events, separated by hundreds of millions of years, conspired to produce the effect.
The first event was the rise of the Ancestral Rocky Mountains during the Pennsylvanian and Permian periods. That uplift supplied the sediment for the Fountain Formation and began to deform the older rocks in the region. But the Ancestral Rockies eventually eroded down to their roots, and the area returned to relative quiet during much of the Mesozoic.
The second and more consequential event was the Laramide Orogeny, roughly 70 to 40 million years ago, which built the modern Rocky Mountains. Compressive forces from the west shoved large blocks of Precambrian basement rock upward along steep faults. At Garden of the Gods, two major range-bounding structures, the Ute Pass fault and the Rampart Range fault, converge in the area west of the park.4GeoScienceWorld. Garden of the Gods at Colorado Springs: Paleozoic and Mesozoic sedimentation and tectonics As the mountain block pushed upward and eastward, the sedimentary layers draped along its flank were bent, folded, and ultimately rotated into their present near-vertical orientation. The park sits right on the eastern flank of the Colorado Front Range, exactly where the rigid mountain block meets the softer sedimentary cover.6GeoScienceWorld Books. The Garden of the Gods and basal Phanerozoic nonconformity in and near Colorado Springs, Colorado
The result is a cross-section through time that you can read like an open book. Walking east from the mountain front, you cross progressively younger rock layers, each one standing on edge and facing you. This is why geologists love the site: in a single park, you can literally walk through hundreds of millions of years of depositional history without ever losing sight of the structural forces that rearranged it all.
Where the Red Color Comes From
The intense red-to-orange color of the Fountain Formation is the single most recognizable feature of Garden of the Gods, and it has a simple chemical explanation: iron oxide. The granitic source rocks that were being eroded to form the Fountain Formation contained iron-bearing minerals like biotite and hornblende. As these minerals broke down during weathering and transport, the released iron oxidized, essentially rusting, and coated the sand grains with a thin film of hematite. Even a tiny amount of hematite is enough to stain rock a vivid red.
The coloring is not uniform throughout the park. Some Fountain Formation exposures lean more toward orange or even pinkish hues depending on the concentration of iron oxide, the grain size, and how much chemical weathering has occurred since the rock was exposed. The Lyons Sandstone, deposited slightly later, often appears paler, ranging from cream to salmon, because its grains were reworked and better sorted by wind, which can dilute the iron-oxide coating. Cretaceous shales and limestones in the park tend toward gray and tan, since they were deposited in marine environments with different chemistry.
One common misconception is that the rocks are red because of the present-day climate. In fact, the oxidation happened at the time of deposition or shortly afterward, during the Permian, when the Colorado region sat near the equator in a hot, semi-arid climate. The red color is baked into the rock’s history, not a product of modern desert sun.
How Erosion Sculpted the Fins and Spires
Standing the rocks on edge was only half the story. Once the Laramide Orogeny tilted the beds vertical, tens of millions of years of erosion went to work carving them into the fins, spires, and balanced rocks that define the park today. The mechanics are straightforward but the results are spectacular.
When a thick, originally horizontal rock layer is tilted vertically, it presents its edge to the surface. Weathering attacks the exposed edge unevenly. Joints, the natural fracture planes that form in any rock body as it is stressed and unloaded, run through the formation at regular intervals. Water, ice, and plant roots exploit these joints, slowly widening them into gaps. Over time, what was once a continuous slab becomes a series of parallel fins separated by narrow corridors. Where a fin is thinner or more heavily jointed, it may erode into a freestanding spire or a dramatic balanced rock perched on a narrow pedestal.
The contrast between hard and soft layers also plays a role. The coarser, more cemented beds within the Fountain Formation resist erosion better than the fine-grained siltstone and mudstone interbeds. As the softer layers erode away preferentially, the harder beds are left standing in relief. This differential weathering is why the park’s formations are not smooth walls but instead a jagged skyline of protruding fins and recessed notches.
Frost wedging is particularly effective in the Colorado Springs climate, where winter temperatures regularly cycle above and below freezing. Water seeps into cracks during the day, freezes and expands at night, and slowly pries the rock apart. Chemical weathering also contributes, especially the breakdown of feldspar grains into clay minerals, which weakens the rock from within. The combination of mechanical and chemical weathering, working along joints and between hard and soft layers, has produced the landscape visitors see today.
The Lyons Sandstone and Its Different Character
While the Fountain Formation gets most of the attention, the Lyons Sandstone deserves a closer look because it forms some of the park’s most distinctive features and has a noticeably different texture. Deposited during the Permian, after the Fountain Formation, the Lyons Sandstone is finer-grained, better sorted, and often displays large-scale cross-bedding that records ancient sand dunes or shallow marine sand bodies. Its beds tend to weather into smoother, more rounded surfaces compared to the rough, pitted faces of the Fountain Formation conglomerates.
The Lyons Sandstone is also commercially significant beyond the park. Historically quarried in several locations along the Colorado Front Range, it has been used as a building stone for over a century. Its attractive color and workability made it a popular choice for foundations, walls, and decorative stonework across the region. Within Garden of the Gods, you can often pick out the Lyons beds by their lighter salmon-to-buff coloring and the sweeping, curved internal bedding planes visible on weathered surfaces. The formation was deposited along the flanks of the Ancestral Front Range alongside the Fountain Formation, but in a somewhat different environmental niche.2The Mountain Geologist. Detrital Zircon Geochronology of Pennsylvanian-Permian Strata in Colorado: Evidence for Appalachian-Derived Sediment and Implications for the Timing of Ancestral Rocky Mountains Uplift
Fossils in the Red Rocks
Most visitors assume the bold red formations are barren of fossils, and for large stretches of the Fountain Formation that intuition is roughly correct. Coarse alluvial deposits tend to be poor fossil preservers because the high-energy rivers that laid them down also tended to destroy delicate organic remains. But the marine intervals within the lower Fountain Formation tell a different story. The trace fossils found in those beds, burrows and tracks left by organisms living on or in the sea floor, were critical evidence in demonstrating that portions of the formation were deposited in marine rather than purely terrestrial settings.3Journal of Paleontology. Trace fossils and marine-nonmarine cyclicity in the Fountain Formation (Pennsylvanian: Morrowan/Atokan) near Manitou Springs, Colorado
Other formations in the park, particularly the Mesozoic layers, have yielded body fossils as well. The Cretaceous shales and limestones, deposited in and around the Western Interior Seaway, contain marine invertebrate fossils typical of that inland sea. And in rocks slightly younger than the main Garden of the Gods sequence, dinosaur fossils and trackways have been found along the Front Range corridor. The park itself is a protected area, so fossil collecting is prohibited, but the geological context makes it clear that these rocks preserve biological as well as geological history.
Reading the Rocks as a Visitor
If you visit Garden of the Gods with even a basic understanding of the geology, the park becomes a much richer experience. The tilted beds create a natural walking transect through time. Starting near the western edge of the park, closest to the mountain front, you encounter the oldest exposed rocks. Walking east, you cross progressively younger formations. The red Fountain Formation dominates the central part of the park and forms the iconic features like Balanced Rock and the North and South Gateway Rocks. The Lyons Sandstone appears as a somewhat lighter-colored band. And the subdued Cretaceous beds along the eastern margin tend to form low ridges and gentle slopes rather than dramatic spires.
The park’s visitor center includes geological exhibits that explain the local stratigraphy, and several of the paved trails have interpretive signs identifying specific formations. For anyone with a geological eye, the real treat is noticing the details within the Fountain Formation itself: the pebble-rich conglomerate beds, the cross-bedding in sandstone layers, the occasional fine-grained interbeds where ancient soils or marine muds were preserved. Each of these textures records a specific moment in the ancient landscape, whether a flash flood, a quiet sea floor, or a riverbank slowly growing vegetation. The entire park is, in effect, a geological museum with the roof removed and the exhibits tilted on their sides.