Carbon cycle and sea-water palaeotemperature evolution at the MiddleeLate Jurassic transition, eastern Paris Basin (France) Pierre Pellenard a, * , Romain Tramoy a, b , Emmanuelle Pucéat a , Emilia Huret c , Mathieu Martinez a , Ludovic Bruneau a , Jacques Thierry d a UMR/CNRS 6282 Biogéosciences, Université de Bourgogne, 6 boulevard Gabriel, 21000 Dijon, France b UMR/CNRS 7193 ISTEP, UPMC Université Paris 06, cc 117, 4 pl. Jussieu, 75252 Paris Cedex 05, France c ANDRA, Parc de la Croix-Blanche, 1-7 rue Jean Monnet, 92298 ChÇtenay-Malabry, France d 15 rue du Point du Jour, 21000 Dijon, France article info Article history: Received 13 March 2013 Received in revised form 24 June 2013 Accepted 4 July 2013 Available online xxx Keywords: Carbon isotopes Oxygen isotopes Sea-water paleotemperatures Paleoenvironmental changes Callovian Oxfordian abstract A very high-resolution carbon and oxygen stable isotope analysis (bulk-carbonate) of a bio- stratigraphically well-constrained CallovianeOxfordian series is provided here for the first time. The homogeneity of the clayey series and the weak diagenetic alteration allow the isotopic signal variations to be considered as primary in origin. A prominent and brief negative excursion in the d 13 C curve (2&), occurring at the start of the Middle Callovian (Jason Zone e Obductum Subzone) and correlated regionally, suggests a possible methane release. The increasing d 13 C values thereafter up to the Early Oxfordian, concomitant with a warming episode, highlight the burial of carbon in organic-rich layers which, in return, may have triggered a decrease in atmospheric pCO 2 . At higher frequencies, observed fluctuations of the d 13 C and d 18 O values are orbitally driven (405-kyr and 100-kyr eccentricity cycles) and may correspond to the salinity and temperature variability recorded in sea water. The d 18 O isotopic measurements from well-preserved diagenetically screened belemnites and bivalves along the series, compared to available data from Tethyan domains, agree with the scenario of a global cooling at the Middle-Late Jurassic transition. The well-dated d 18 O isotopic curve suggests that the onset of this cooling event occurred at the end of the Coronatum Zone (Middle Callovian). Ó 2013 Elsevier Ltd. All rights reserved. 1. Introduction The Jurassic times have long been considered as a period with a relatively stable climate, with high greenhouse gas emissions (“greenhouse period”), where atmospheric pCO 2 constituted the main warming driver (Frakes et al., 1992; Hallam, 1993; Sellwood and Valdes, 1997; Sellwood et al., 2000). Recently, new studies have suggested climatic disturbances at high and low frequencies, with cooling episodes (“cold snaps”) able to produce polar ice-sheet development (Dromart et al., 2003a, b; Brigaud et al., 2008, 2009; Dera et al., 2011). More specifically, for the Middle-Late Jurassic Transition (MLJT), the available sedimentological, mineralogical, palaeontological, palaeobotanical, palynological, and geochemical (stable oxygen and carbon isotopes) data seem to indicate signifi- cant climate change (Abbink et al., 2001; Dromart et al., 2003a, b; Lécuyer et al., 2003; Cecca et al., 2005; Pellenard and Deconinck, 2006; Hautevelle et al., 2006; Nunn et al., 2009). A global cold episode and ice-sheet formation around the CallovianeOxfordian boundary was first proposed by Dromart et al. (2003a, b) based on several global observations: 1) the southward migration of Sub- Boreal ammonites (i.e., Kosmoceratidae and Cardioceratidae) into the Tethyan domain, 2) changes in palynomorph associations and palaeoflora distribution in the Northern Europe hinterlands, 3) the presence of glendonites in the CallovianeOxfordian from north- eastern Asia, 4) a significant sea-level drop (40e80 m) at the end of the Callovian, probably associated to the development of polar ice caps. This latter scenario was tested by a climateecarbon cycle model (Donnadieu et al., 2011), which suggests a possible short- lived cool episode and ice development, linked to the demise of carbonate production. Other recent studies conducted in Europe and Northern Asia, however, refute such climatic changes on a global scale for the MLJT (Wierzbowski et al., 2009; Wierzbowski and Rogov, 2011; Alberti et al., 2012). In contrast, these authors suggest: 1) a major marine transgression during the Late Cal- lovianeEarly Oxfordian transition favouring new palaeogeographic * Corresponding author. Tel.: þ33 3 80 39 63 66; fax: þ33 3 80 39 63 87. E-mail address: Pierre.Pellenard@u-bourgogne.fr (P. Pellenard). Contents lists available at ScienceDirect Marine and Petroleum Geology journal homepage: www.elsevier.com/locate/marpetgeo 0264-8172/$ e see front matter Ó 2013 Elsevier Ltd. All rights reserved. http://dx.doi.org/10.1016/j.marpetgeo.2013.07.002 Marine and Petroleum Geology xxx (2013) 1e14 Please cite this article in press as: Pellenard, P., et al., Carbon cycle and sea-water palaeotemperature evolution at the MiddleeLate Jurassic transition, eastern Paris Basin (France), Marine and Petroleum Geology (2013), http://dx.doi.org/10.1016/j.marpetgeo.2013.07.002