PLIENSBACHIAN STAGE

division representing all rocks deposited worldwide during the Pliensbachian Age (198 to 193 million years ago). It is the third of the 11 divisions (in ascending order) that characterize the Jurassic System. No global stratotype section and point (GSSP) for the base of the Pliensbachian Stage has been approved by the International Commission on Stratigraphy. The stage's name is derived from the village of Pliensbach, which is near Boll, about 40 km (25 miles) southeast of Stuttgart in the Swabian Alps of Germany. The Pliensbachian Stage is represented by up to 195 m (640 feet) of mostly marls in Germany, Belgium, and Luxembourg. Five ammonite biozones, beginning with Uptonia jamesoni and ending with Poltopleuroceras spinatum, are recognized. The stage shows the greatest development of ammonite endemism during the Early Jurassic. Tethyan ammonites from the upper portions of the Pliensbachian occur throughout the circum-Pacific belt, frequently including such genera as Protogrammoceras, Arieticeras, and Fuciniceras. The Pliensbachian Stage overlies the Sinemurian Stage and is itself overlain by the Toarcian Stage.