The base of the Aalenian Stage is defined at the base of Bed FZ 107 in Fuentelsaz Section, Castilian Branch of the Iberian Range, Spain. The boundary coincides with the first occurrence of the ammonite assemblage characterized by Leioceras opalinum and Leioceras lineatum and corresponds with a normal polarity interval.
The GSSP of the Aalenian Stage is located at 0.5km to the North of Fuentelsaz village, NE of Guadalajara province, Central Sector of the Castilian Branch in the Iberian Range; about 170km to the ENE of Madrid and 30km to the N of Molina de Aragón. The GSSP is located at a latitude of 41°10'15"N and a longitude of 1°50'W.
The GSSP succession is composed of marls with interbedded limestones forming an irregular rhythmic alternation. Marls are dominant in the upper part of the Pleydellia aalensis Subzone and in the Pleydellia buckmani Subzone. Carbonates become more important near the Toarcian - Aalenian Boundary. The Toarcian - Aalenian Boundary is defined at Bed FZ 107.
The boundary coincides with the first occurrence of the ammonite assemblage characterized by Leioceras opalinum and Leioceras lineatum.
Hexalithus magharensis appears first in Bed FZ 107.
Ammonite FAD Leioceras opalinumand Leioceras lineatum
Duration of Aalenian-Toarcian from cycle stratigraphy
Cresta, S., Goy, A., Ureta, S., Arias, C., Barrón, E., Bernard, J., Canales, M. L., García-Joral, F., García-Romero, E., Gialanella, P. R., Gomes, J. J., González, J. A., Herrero, C., Marínez, G., Osete, M. L., Perilli, N., and Villalaín, J. J., 2001. The Global Boundary Stratotype Section and Point (GSSP) of the Toarcian - Aalenian Boundary (Lower - Middle Jurassic). Episodes 24/3, p.166 - 175.