Fiskeler

The fiskeler was discovered by Søren Abildgaard in 1759^[3][4] and was named fiskeler by Johan Georg Forchhammer in 1826^[5] before being described by Richard Taylor and Richard Phillips in 1827.^[6] Charles Lyell noted the absence of fossils in 1835,^[7] while Forchhammer was able to locate fossils at the site in 1849, using the name fiskeler for the first time in published literature.^[8]

It was linked to the Cretaceous–Paleogene boundary during 1980 as a reference point for the stratigraphy and iridium content from the Chixculub impactor which struck Mexico.^[2]

The dark marl layer of fiskeler, mainly five to ten centimeters thick, clearly marks the Cretaceous–Paleogene boundary^[9] and overlies the Maastrichtian age Tor Formation as an unconformity.^[10][11][12] 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.^[13] It also suggested that when the fiskeler was deposited, a sudden change in the local sea level occurred.^[14]

It overlies the Cerithium Limestone Member which is Danian in age and contains Paleocene ammonites.^[1][15]

The fiskeler contains fossils of animals directly killed by the Chixculub impactor, including an abundance of scales and teeth from fish (with most being microscopic in size),^[1] with few other fossils of which include mussels and zoophytes.^[5] The first chondrichthyan fossils (including thirty-one distinct species and one indeterminate specimen) from the fiskeler were described by Adolfssen & Ward (2014).^[14] This suggested the fauna was similar to Maastrichtian Germany and Danian Sweden,^[16][17] linking the fiskeler to the Tethys Ocean.^[18]

Only one three-dimensional fish specimen has been found within the fiskeler, and it was described by Forchammer (1849).^[8] It is missing the tail and head, and it probably belonged to Berycidae.^[4]