LEONARDIAN STAGE

post-Wolfcampian time of deposition of the Lower Permian Series of rock strata in the United States, especially well-developed in the Southwest (the Permian Period began about 280,000,000 years ago and lasted about 55,000,000 years). The Leonardian is defined on the basis of exposures seen in the Lenox hills in the Glass Mountains, Texas, where it consists of more than 600 m (2,000 feet) of gray, silty shales interbedded with light-gray limestones. In central Texas, Leonardian strata are seen as red beds, channel sandstones, gray shales, and thin, widespread limestones. These strata contain a well-developed reptile and amphibian faunal assemblage. In the Guadalupe Mountains and the Diablo Mountains, wholly marine Leonardian strata exhibit two strikingly distinct facies: a white limestone, the Victorio Peak Limestone, and a black, thin-bedded limestone formation, the Bone Spring Limestone. The Victorio Peak Limestone was deposited on a broad platform with shallow lagoons; the black Bone Spring Limestone accumulated in deep, poorly oxygenated, fetid basins where conditions were inimical to life and organically rich sediments accumulated slowly.