The Rødvig Formation is a geological formation deposited during the earliest part of the Danian (early Paleocene; c. 65-62 Ma[1]) and it was first identified by Richard Taylor and Richard Phillips in 1827.[2] It is known from exposures at Stevns Klint in Denmark. The unit lies directly above the K–Pg boundary and contains fossils that provide a record of the recovery of various groups following the Cretaceous–Paleogene extinction. The upper boundary of the formation is an unconformity in the form of a hardground, beneath which the formation is sometimes missing. The base of the unit is irregular due to the presence of mounding associated with bryozoa, causing variations in thickness. The unit is subdivided into the lower Fiskeler Member mainly formed of marl and the overlying Cerithium Limestone Member.[3]
Geology
The three fossil formations of Stevns Klint, with the Rødvig Formation in the middle
The dark layer of fiskeler,[a] mainly five to ten centimeters thick, clearly marks the Cretaceous–Paleogene boundary and overlies the Maastrichtian age Tor Formation.[5] The fiskeler is enriched in iridium, a fact used as an argument for the Alvarez hypothesis that the worldwide Cretaceous–Paleogene mass extinction was caused by the impact of an asteroid. Following the boundary is a layer of darker clay and chalk between 10 and 30 cm thick, corresponding to a period of low biological diversity on the sea floor immediately after the K-Pg Boundary.[6]
Paleontology
The Rødvig Formation contains a remarkably detailed and complete fossil record of the biota in Northern Europe during the early Paleogene. The layers are rich in microfossils, containing many species of millimeter-long suspension feeders.[7] A wide variety of benthicforaminifera species have been identified from the Rødvig Formation, with significant differences in abundance across the K–Pg boundary demonstrating the biotic turnover that occurred during the mass extinction event.[7]
The Rødvig Formation was the first known site to document the short-term survival of ammonites into the Paleogene, when they were originally thought to have gone extinct at the K-Pg boundary.[8][9][10][11][12][13] Ammonites are thus only known from the first 200,000 years of the Cerithium Limestone, before disappearing from the formation around 64.8 million years ago.[10][13]
^A Danish word that is traditionally used by geologists as a label for this layer, parallel to its English translation "Fish Clay". It was given this name by the Danish geologist Johan Georg Forchhammer in 1825, as it contained scales and teeth from fish, but few other fossils.[4][full citation needed]
^Taylor, R. & Phillips, R. (1827). The Philosophical magazine, or Annals of chemistry, mathematics, astronomy, natural history and general science. London : Richard Taylor (p. 99)
^Westermann, G. E. G. (1996). Ammonoid life and habitat. In N. H. Landman, K. Tanabe, and R. A. Davis (editors), Ammonoid Paleobiology, pp. 607–707. New York: Plenum Press.
