Argovian Formation

Argovian Formation
Stratigraphic range: Jurassic
TypeFormation
Location
CountryFrance, Switzerland

The Argovian Formation (French: Argovien) is a geologic formation in France. It preserves fossils dating back to the Jurassic period.[1][2][3]

Location and structure

The Argovian is a stratigraphic unit and facies of the Upper Jurassic (specifically the Middle to Upper Oxfordian), primarily identified in the Jura Mountains of France and Switzerland, as well as the Paris Basin.[4] Historically considered a distinct stage, modern stratigraphy typically classifies it as a facies characterized by alternating marls and spongiolitic limestones, often corresponding to the Terrain à Chailles or Birmenstorf Member in regional lithostratigraphy.[5] The formation marks a transition in the sedimentary environment of the Tethys Ocean shelf, representing deeper subtidal waters that favored the growth of extensive siliceous sponge bioherms (sponge reefs) rather than the shallow coral reefs found in adjacent facies.[6]

Paleontology

Paleontologically, the Argovian layers are significant for their rich and well-preserved marine fauna. The unit yields diverse ammonite assemblages, including species of Cardioceras, Perisphinctes, and Ochetoceras canaliculatum, which are essential for biostratigraphic dating of the Oxfordian age.[7] In eastern France, the Argovian facies (specifically the Terrain à Chailles) acts as a Lagerstätte, preserving soft-bodied organisms and articulated crustaceans such as glypheoid lobsters in distinct siliceous nodules.[4] The abundance of siliceous sponges in these strata has led to the historical designation of these layers as the "Spongitien" facies in older geological literature.[6]

References

  1. ^ Torrens, Hugh S. (2002). "From d'Orbigny to the Devonian: some thoughts on the history of the stratotype concept". Comptes Rendus Palevol. 1 (6): 335–345. doi:10.1016/S1631-0683(02)00064-7.
  2. ^ A. A. Baker; C. H. Dane; J. B. Reeside, Jr. "Correlation of the Jurassic Formations" (PDF). USGS Publications Warehouse. Retrieved 2025-11-25. The Curtis formation is interpreted as represented in the area considered in this paper by several fairly well defined lobes extending southeastward. The Entrada sandstone is interpreted as extending widely into Colorado, where it forms the lower part of the typical Entrada sandstone of northwestern Colorado. The San Rafael group is assigned to the Upper Jurassic; the Carmel formation to the basal part of the European standard section (Callovian) and the Curtis to the middle part (Argovian), on the basis of their marine fossils.
  3. ^ Ralph W. Imlay (2019-09-17). "Jurassic Formations of Gulf Region". AAPG Bulletin. Retrieved 2025-11-25. The upper parts of the La Gloria and Zuloaga formations belong to the Argovian substage of the Oxfordian, but their lower parts may be as old as the Callovian.
  4. ^ a b Charbonnier, Sylvain; Pérès, Dimitri; Letenneur, Charlène (2012). "Exceptionally preserved crustaceans from the Oxfordian of eastern France (Terrain à Chailles Formation)". Geodiversitas. 34 (3): 531–568. doi:10.5252/g2012n3a5.
  5. ^ Gygi, Reinhart A. (2000). "Lithostratigraphy of the Oxfordian and Kimmeridgian (Late Jurassic) in northern Switzerland". Eclogae Geologicae Helvetiae. 93: 125–154.
  6. ^ a b N. Theobald. "Paléogéographie du Jurassique Supérieur dans le Sud-Ouest de l'Allemagne et le Nord-Ouest de France" (PDF). Zobodat. Naturforschende Gesellschaft zu Freiburg im Breisgau. Retrieved 2025-12-21.
  7. ^ Lais, R. (1925). "Zwischen Maas und Mosel" (PDF). Bulletin de la Société des Sciences de Nancy: 39–42.
allikas: https://en.wikipedia.org/wiki/Argovian_Formation