The preserve is situated in northern Dallas County, and features old-growth bottomlandforest with a gentle, wide spring water stream that flows over a bed of solid limestone. The force of the water has cut cliffs from the surrounding Austin Chalk. The towering 20- to 40-foot-tall cliffs contain Cretaceous fossils dated at 87 million years old, a combination primarily found only in Garland. Austin Chalk is also found in the eastern portion of the DFW Metroplex heading toward the Texas Hill Country. Several geologic formations are interspersed along the last five miles (8.0 km) of the creek located in Garland and Richardson. The entire length of the creek, named Spring Creek, is spring fed at a constant 72 °F. The swift water of Spring Creek varies in depth between one and six feet and is about 20 feet (6.1 meters) wide. Even in years of extreme drought, it has never run dry. The water clarity allows one to watch the native Longear Sunfish, which can be seen gliding along against the white, limestone bottom. The abundant water supply has allowed the forest to survive for centuries. Some of the trees in the forest are as much as 500 years old and tower 100 feet on trunks that are 4 feet in diameter. Five varieties of oak live in the forest, including chinquapin, bur, and shumard, a combination found nowhere else in the world. Native plants include the solomon’s seal, horsetails and Pennsylvania violet (Viola pennsylvanicum). More than 630 species of plants and animals have been observed in addition to the many species of dragonflies, spiders, mites, beetles, fungi, and ants living in the forest.