Platinum group elements and 187 Os/ 188 Os in a purported impact ejecta layer near the Eifelian–Givetian stage boundary, Middle Devonian Birger Schmitz a, ⁎ , Brooks B. Ellwood b , Bernhard Peucker-Ehrenbrink c , Ahmed El Hassani d , Pierre Bultynck e a Department of Geology, University of Lund, Sölvegatan 12, SE-22362 Lund, Sweden b Department of Geology and Geophysics, Louisiana State University, E235 Howe-Russell Geoscience Complex, Baton Rouge, LA 70803, USA c Department of Marine Chemistry and Geochemistry, Woods Hole Oceanographic Institution, 360 Woods Hole Road, Woods Hole, MA 02543, USA d Département de Géologie, Institut Scientifique, B.P. 703, Rabat-Agdal, Morocco e Department of Paleontology, Royal Belgian Institute of Natural Sciences, rue Vautier 29, BE-1000 Brussels, Belgium Received 24 April 2006; received in revised form 10 July 2006; accepted 12 July 2006 Available online 17 August 2006 Editor: R.W. Carlson Abstract A global faunal crisis close to the Eifelian–Givetian stage boundary in the mid-Devonian has been purported to be related to the impact of one or two major extraterrestrial bodies. This was based on unusual mineralogical and chemical features within a distinct composite marl bed, at a level c. 40 cm below the Global Stratotype Section and Point (GSSP) for the Eifelian–Givetian boundary at Jebel Mech Irdane in Morocco. The impact relation has been challenged based partly on the absence of platinum group element data. We present here detailed Ir, Os, Pd and Pt as well as Os isotopic data across the bed at Mech Irdane and from a correlated 10 cm bed at a nearby site, Rich Haroun. Iridium concentrations of 0.13–0.28 ng/g in the beds represent a small enrichment compared to average shale, but Ir/Al ratios are only a factor 1.5–2 higher than background at respective site. Such small enrichments can readily be explained by terrestrial diagenetic processes, and do not require the presence of an extraterrestrial component. On an Al-normalized basis Pd and Pt show weak enrichments, typically a factor 2–4 higher than background. High 187 Os/ 188 Os ratios, 1.1–3.8, reflect ingrowth of radiogenic Os from Re, which is also evident from Os concentrations of up to 3 ng/g. The platinum group inter-element ratios are clearly non-chondritic. The overall platinum group and trace element (e.g. Co, Ni, As, V) patterns indicate that diagenetic processes at redox fronts have played a crucial role in shaping most element enrichments. If an excess siderophile-rich extraterrestrial component exists in these beds it represents less than 0.2‰ by weight. © 2006 Elsevier B.V. All rights reserved. Keywords: Eifelian–Givetian boundary; iridium; platinum group elements; asteroid impact; mass extinctions 1. Introduction The discovery of a precise stratigraphic coincidence at the Cretaceous–Paleogene (K–P) boundary of a major Earth and Planetary Science Letters 249 (2006) 162 – 172 www.elsevier.com/locate/epsl ⁎ Corresponding author. Tel.: +46 46 2227869; fax: +46 46 2224419. E-mail address: birger.schmitz@geol.lu.se (B. Schmitz). 0012-821X/$ - see front matter © 2006 Elsevier B.V. All rights reserved. doi:10.1016/j.epsl.2006.07.024