Aalenian

Aalenian
174.7 ± 0.8 – 170.9 ± 0.8 Ma
The Aalenian GSSP in Spain
Chronology
Etymology
Name formalityFormal
Usage information
Celestial bodyEarth
Regional usageGlobal (ICS)
Time scale(s) usedICS Time Scale
Definition
Chronological unitAge
Stratigraphic unitStage
Time span formalityFormal
Lower boundary definitionFAD of Ammonites Leioceras opalinum and Leioceras lineatum
Lower boundary GSSPFuentelsaz, Spain
41°10′15″N 1°50′00″W / 41.1708°N 1.8333°W / 41.1708; -1.8333
Lower GSSP ratified2000[2]
Upper boundary definitionFAD of the Ammonites Hyperlioceras mundum, Hyperlioceras furcatum, Braunsina aspera, and Braunsina elegantula
Upper boundary GSSPCabo Mondego, Portugal
40°11′57″N 8°54′15″W / 40.1992°N 8.9042°W / 40.1992; -8.9042
Upper GSSP ratified1996[3]

The Aalenian ( /ɑːˈlniən/) is a subdivision of the Middle Jurassic Epoch/Series of the geologic timescale that extends from about 174.7 ±0.8 Ma to about 170.9 ±0.8 Ma (million years ago). It was preceded by the Toarcian and succeeded by the Bajocian.[4]

  1. ^ "International Chronostratigraphic Chart" (PDF). International Commission on Stratigraphy.
  2. ^ Cresta, S.; Goy, A.; Arias, C.; Barrón, E.; Bernad, J.; Canales, M.; García-Joral, F.; García-Romero, E; Gialanella, P.; Gómez, J.; González, J.; Herrero, C.; Martínez2, G.; Osete, M.; Perilli, N.; Villalaín, J. (September 2001). "The Global Boundary Stratotype Section and Point (GSSP) of the Toarcian-Aalenian Boundary (Lower-Middle Jurassic)" (PDF). Episodes. 24 (3): 166–175. doi:10.18814/epiiugs/2001/v24i3/003. Retrieved 13 December 2020.{{cite journal}}: CS1 maint: numeric names: authors list (link)
  3. ^ Pavia, G.; Enay, R. (March 1997). "Definition of the Aalenian-Bajocian Stage boundary". Episodes. 20 (1): 16–22. doi:10.18814/epiiugs/1997/v20i1/004. Retrieved 23 December 2020.
  4. ^ See Gradstein et al. (2004) for a detailed version of the geologic timescale