Possible traces of the impactor on fracture surfaces of shattered belemnites from the Nördlinger Ries crater (Southern Germany) and potential consequences for the classification of the Ries impactor
Buchner, Elmar; Schmieder, Martin
published: Jun 1, 2017
published online: Jul 31, 2017
ArtNo. ESP171016802003, Price: 29.00 €
The Nördlinger Ries crater counts among the most thoroughly studied impact structures on Earth with respect to crater forming processes and the evolution and distribution of its impact ejecta. In contrast, little is known about the character of the impacting body that formed the Nördlinger Ries/Steinheim Basin crater doublet. Based on the element ratios of Fe/ Ni, Ni/Co and Ni/Cr, as well as of the platinum group elements, an achondritic (aubrite) or chondritic (carbonaceous chondrite) projectile was previously suggested as the Ries impactor. We here report, for the first time, on the somewhat surprising discovery of likely meteoritic matter on the fracture surfaces of shattered Ries belemnites. These shocked fossils occur in a block of Upper Jurassic limestones forming part of the eastern morphological crater rim of the Nördlinger Ries, exposed in the Gosheim limestone quarry. From their geochemical composition, metallic veinlets on the belemnite fracture surfaces strikingly resemble metal veins, earlier described from basement rocks, drilled close to the crater centre in 1973. The interelement ratios between Fe, Ni, Cr and Co in our samples seem to hint at an iron (or stony-iron) meteoritic projectile, although this is in conflict with previous studies that favour a chondritic or achondritic Ries projectile.