An ocean frozen in stone
The towering limestone pillars of the Shilin Stone Forest look like a landscape from another world, but they are actually the remnants of our own. About 270 million years ago, during the Permian period, this entire region was a warm, shallow sea. For millions of years, the skeletal remains of marine organisms accumulated on the seabed, forming a thick layer of carbonate mud. This sediment eventually became the massive limestone beds of the Qixia and Maokou Formations seen today.
After the sea retreated, immense geological pressure caused the land to rise. This newly exposed limestone plateau became subject to erosion. Rainwater, made slightly acidic by carbon dioxide from the atmosphere, seeped into cracks in the rock, slowly dissolving the limestone and carving the deep, narrow fissures that define the forest. This process, which continues today, has sculpted the rock into a dense collection of pillars, some reaching over 40 meters in height. The stone spires are a example of karst topography, a landscape shaped by the dissolution of soluble rock.
A catalog of ancient life
The stone pillars are geological curiosities; they are a record of ancient life. The limestone is exceptionally full of marine fossils from the Permian period. As the rock weathers and breaks apart, it exposes the preserved forms of creatures that died 270 million years ago. Some rock layers are composed almost entirely of biological debris.
The fossilized ecosystem includes a diverse community of organisms. Scientists have identified reef-building lifeforms like corals and sponges, as well as brachiopods, gastropods, cephalopods, and bryozoans. Also common are fusulinids, a type of single-celled organism that built shells resembling grains of rice. By mapping the location of these fossils on the surfaces of the pillars, paleontologists can reconstruct the structure of the ancient reef. This work provides a detailed record of a marine world that existed long before the dinosaurs, just prior to the largest mass extinction event in Earth's history, the Permian-Triassic extinction, which eliminated over 90% of all marine species.