Paleoenvironmental changes during the Valanginian: New insights from variations in phosphorus contents and bulk- and clay mineralogies in the western Tethys Stéphane Westermann a,b, ⁎, Stéphanie Duchamp-Alphonse c , Nicolas Fiet d , Dominik Fleitmann e,f , Virginie Matera g , Thierry Adatte b , Karl B. Föllmi b a Institute of Geochemistry and Petrology, ETH Zürich, Clausiusstrasse 25, 8092 Zürich, CH, Switzerland b Institute of Earth Sciences, University of Lausanne, Géopolis, 1015 Lausanne, Switzerland c UMR 8148-I.D.E.S., Bât. 504, University of Paris Sud, 91405 Orsay Cedex, France d AREVA, 33 Rue La Fayette, 75009 Paris, France e Institute of Geological Sciences, University of Bern, Baltzerstrasse 1-3, 3012 Bern, Switzerland f Department of Archaeology, School of Human and Environmental Sciences, University of Reading, RG6 6AB Reading, UK g IRSN, Avenue de Bourgogne, 54500 Vandoeuvre-Les-Nancy, France abstract article info Article history: Received 20 September 2012 Received in revised form 16 August 2013 Accepted 19 September 2013 Available online 25 September 2013 Keywords: Clay mineralogy Detrital index Phosphorus Valanginian Climatic changes Carbon cycle perturbation Tethys Paleoenvironmental and paleoclimatic changes during the Valanginian carbon isotopic excursion (CIE) have been investigated in the western Tethys. For this purpose, bulk-rock and clay mineralogies, as well as phosphorus (P) contents were evaluated in a selection of five sections located in the Vocontian Basin (Angles, SE France; Alvier, E Switzerland; Malleval, E France), and the Lombardian Basin (Capriolo, N Italy; Breggia, S Switzerland). Within the CIE interval, bulk-rock and clay mineralogies are inferred to reflect mostly climate change. The onset of the CIE (Busnardoites campylotoxus ammonite Zone) is characterized by higher detrital index (DI: sum of the detrital minerals divided by calcite contents) values and the presence of kaolinite in their clay-mineral assem- blages. In the late Valanginian (from the Saynoceras verrucosum Zone up to the end of the Valanginian), the sam- ples show relatively variable DI and lower values or the absence of kaolinite. The variation in the mineralogical composition is interpreted as reflecting a change from a climate characterized by optimal weathering conditions associated with an increase in terrigenous input on the southern European margin during the CIE towards an overall unstable climate associated with drier conditions in the late Valanginian. This is contrasted by a dissym- metry (proximal vs distal) along the studied transect, the northern Tethyan margin being more sensitive to changes in continental input compared to the distal environments. P accumulation rates (PAR) present similar features. In the Vocontian basin, P content variations are associated with changes in terrigenous influx, whereas in the Lombardian basin (i.e. Capriolo and Breggia), PAR values are less well correlated. This is mainly because the deeper part of the Tethys was less sensitive to changes in continental inputs. The onset of the CIE (top of the B. campylotoxus Zone) records a general increase in PAR suggesting an increase in marine nutrient levels. This is linked to higher continental weathering rates and the enhanced influx of nutrients into the ocean. In the period corresponding to the shift itself, P contents show a dissymmetry between the Vocontian and Lombardian basins (proximal vs distal). For the sections of Malleval, Alvier and Angles, a decrease in P concentrations associated to a decrease in detrital input is observed. In Capriolo and Breggia, PAR show maximum values during the plateau, indicating a more complex interaction between different P sources. The time interval including the top of S. verrucosum Zone up to the end of the Valanginian is characterized by variable PAR values, suggesting variable nutrient influxes. These changes are in agreement with an evolution towards seasonally contrasted conditions in the late Valanginian. © 2013 Elsevier B.V. All rights reserved. 1. Introduction The Valanginian includes the first major perturbation in the Creta- ceous carbon cycle, the so-called “Weissert event” (Erba et al., 2004), which is defined by a positive excursion in marine carbonate- and marine and terrestrial organic-carbon isotope records (Lini et al., 1992; Föllmi et al., 1994; Weissert et al., 1998; Hennig, 2003; Erba et al., Palaeogeography, Palaeoclimatology, Palaeoecology 392 (2013) 196–208 ⁎ Corresponding author at: Institute of Geochemistry and Petrology, ETH Zürich, Clausiusstrasse 25, 8092 Zürich, CH, Switzerland. Tel.: +41 44 632 37 45; fax: +41 44 632 11 12. E-mail address: stephane.westermann@erdw.ethz.ch (S. Westermann). 0031-0182/$ – see front matter © 2013 Elsevier B.V. All rights reserved. http://dx.doi.org/10.1016/j.palaeo.2013.09.017 Contents lists available at ScienceDirect Palaeogeography, Palaeoclimatology, Palaeoecology journal homepage: www.elsevier.com/locate/palaeo