ELSEVIER Palaeogeography, Palaeoclimatology, Palaeoecology 133 (1997) 49-68 PMIE0 High-resolution iridium, 613C, 6180, foraminifera and nannofossil profiles across the latest Paleocene benthic extinction event at Zumaya, Spain Birger Schmitz a,., Frank Asaro b, Eustoquio Molina c Simonetta Monechi d, Katharina von Salis °, Robert P. Speijer a,1 a Department of Marine Geology, Earth Sciences Centre, University of GOteborg, S-413 81 GOteborg, Sweden b Lawrence Berkeley National Laboratory, MS 195/Bldg 70, University of California, Berkeley, CA 94720, USA c Departamento de Geologia (Paleontologia), Facultad de Ciencias, Universidad de Zaragoza, 50009 Zaragoza, Spain d Dipartimento di Scienze della Terra, Universita di Firenze, Via La Pira 4, 50121 Firenze, Italy e Geological Institute, Swiss Federal Institute of Technology, CH-8092 Zfirich, Switzerland Received 4 January 1996; accepted 29 January 1997 Abstract In the expanded upper Paleocene-lower Eocene section (~ 30 m of Zone P5 sediments) at Zumaya, northern Spain, the highest occurrence of many late Paleocene deep-sea benthic foraminifera species (~40% extinction), coincides with a transition from marl to calcite-free clay. Our high-resolution studies (chemical elements, 613C, 6180, calcareous nannofossils, planktic and benthic foraminifera) show that below the marl-clay transition there is a 40-50 cm thick interval (corresponding to 10-20 kyr) containing a detailed record of a gradual succession of faunal and geochemical events culminating in the benthic extinctions. Planktic foraminiferal and nannofossil changes (e.g., the onset of demise in Fasciculithus genus) occur a few meters below the marl-clay transition. In the limestone 50 cm below the base of the clay, a prominent glauconite maximum indicates that sea-floor oxygenation suddenly decreased. Glauconite continues to be common until the onset of clay deposition. A whole-rock negative 613C shift (1.6%0), most likely reflecting an original sea-water trend, is gradually developed over the 40 cm of greenish brown marls immediately below the clay. At the base of these marls there is a small, significant iridium anomaly of 133 ppt Ir compared with an average background of 38 ppt. In the marls the demise of the Fasciculithus species accelerates, Gavelinella beccariiformis becomes extinct, and the abundance of Acarinina species begins to increase. The superjacent 4 m of clay is devoid of original calcite in its lower part and has a low calcareous content higher up. At calcareous levels in the clay an unusual planktic foraminifera fauna occurs, dominated by Acarinina species. When marl deposition returns, 613C gradually increases and then stabilizes at values about 0.5%o lower than before the isotopic excursion. The 613C excursion spans in total 5 m, probably corresponding to 200-400 kyr. The fasciculiths disappear shortly after the stabilization of 613C. Here we also present a whole-rock 6~3C profile through the entire Paleocene section at Zumaya. The profile is very similar to previous profiles registered in well preserved deep-sea material, suggesting that whole-rock 613C at Zumaya can be used for correlation. * Corresponding author. Fax: + 46 31 7734903. E-mail: birger@gvc.gu.se ~Present address: University of Bremen, FB 5, Geosciences, Box 330440, 28334 Bremen, Germany. 0031-0182/97/$17.00 © 1997 Elsevier Science B.V. All rights reserved. PH S0031-0182(97)00024-2