1911 Encyclopædia Britannica/Aptian

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APTIAN (Fr. Aptien, from Apt in Vaucluse, France), in geology, the term introduced in 1843 by A. d’Orbigny (Pal. France Crét. ii.) for the upper stage of the Lower Cretaceous rocks. In England it comprises the Lower Greensand and part of the Speeton beds; in France it is divided into two sub-stages, the lower, “Bedoulian,” of Bedoule in Provence, with Hoplites deshayesei and Ancyloceras Matheroni; and an upper, “Gargasian,” from Gargas near Apt, with Hoplites furcatus (Dufrenoyi) and Phylloceras Guettardi. To this stage belong the Toucasia limestone and Orbitolina marls of Spain; the Schrattenkalk (part) of the Alpine and Carpathian regions; and the Terebrirostra limestone of the same area. Parts of the Flysch of the eastern Alps, the Biancone of Lombardy, and argile scagliose of Emilia, are of Aptian age; so also are the “Trinity Beds” of North America. Deposits of bauxite occur in the Aptian hippurite limestone at Les Baux near Arles, and in the Pyrenees. The Aptian rocks are generally clays, marls and green glauconitic sands with occasional limestones. (See Greensand and Cretaceous.)