Sandstone formations preserve 400-million-year-old desert dunes that once covered this region. You can see the preserved wind patterns in the rock layers. An ancient Sahara frozen in stone in southern Brazil.
Luiz Eduardo Schramm, CC BY-SA 3.0
A Desert at the South Pole
The sandstone sculptures of Vila Velha State Park are remnants of a landscape different from modern Brazil. They belong to the Ponta Grossa and Furnas Formations, geological units deposited during the Devonian Period, approximately 400 million years ago. At that time, this part of South America was attached to Africa as part of the supercontinent Gondwana. The continent was positioned at a much higher latitude, placing the Paraná Basin—an intracratonic depression covering 1.5 million square kilometers—near the South Pole.
The whitish, coarse-grained sandstone of the Furnas Formation represents a coastal environment, where fluvial systems met a shallow sea. Visible within these rocks are distinct layers and patterns known as planar cross-bedding. These structures are the fossilized remains of large sand dunes, shaped by persistent winds blowing across an arid, cold desert. The layers show the direction and angle of the ancient wind, freezing a 400-million-year-old weather report in stone. The entire Paraná Group, which includes these formations, reaches a maximum thickness of 800 meters.
From Sea Floor to Sculpted Towers
Above the desert sands, the geological story shifts. A global rise in sea level is recorded by the transition to the dark, fine-grained shales of the Ponta Grossa Formation. This unit was deposited in a shallow marine environment that flooded the earlier desert. These marine rocks contain a collection of Devonian fossils known as the Malvinokaffric fauna. This fossil assemblage includes trilobites, brachiopods, gastropods, and Tentaculitoidea, which are small, conical shelled invertebrates. These creatures thrived in the cold, high-latitude waters that covered the region.
The striking shapes seen today—resembling a goblet or a camel—are not from the Devonian; are the product of millions of years of erosion. After the layers of sand and mud lithified into rock and were uplifted, wind and water began to exploit weaknesses. The sandstone is cemented by materials of varying hardness. Softer sections wear away more quickly, a process called differential erosion, leaving behind the more resistant portions as free-standing sculptures. The entire park covers 3,803 hectares, preserving these geological monuments.
💡Fun Facts
The region was affected by the Ponta Grossa Arch, a major upward warping of the crust that occurred 130 million years ago during the breakup of Gondwana.
Fossils found in the marine layers of the Ponta Grossa Formation show a high degree of endemism, meaning the species were unique to this cold-water region near the South Pole.
The Paraná Basin, in which these rocks sit, holds the Guarani Aquifer, one of the largest freshwater aquifer systems in the world.
The reddish color of some of the sandstone is due to the presence of iron oxide, which acted as a cementing agent for the original sand grains.
