HETTANGIAN STAGE

the lowest of 11 stages in the Jurassic System, consisting of rocks deposited globally during the Hettangian Age (208 to 204 million years ago). It directly underlies the Sinemurian Stage. Nominally, the base of the Hettangian Stage defines the upper limit of the Triassic System; however, no global stratotype section and point (GSSP) has been approved for its base. The name Hettangian refers to the type district for the stage, located at the village of Hettange-Grande, near Thionville in Lorraine, France. The type district consists of a thick succession (57-70 m [187-230 feet]) of basal sandstones overlain by limestones and marls. The limestones bear the bivalve Gryphaea arcuata and other fossils correlative to the ammonite biozone of Psiloceras planorbis. Other species of this genus occur throughout eastern Siberia, North America, and South America. The upper part of the Hettangian Stage in Europe is subdivided by species of the ammonite genus Schlotheimia, which also occurs in North and South America.