Monteiro F M Pancost R D Ridgwell A J

Monteiro F M Pancost R D Ridgwell A J-Free PDF

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PALEOCEANOGRAPHY VOL 27 PA4209 doi 10 1029 2012PA002351 2012. Nutrients as the dominant control on the spread of anoxia. and euxinia across the Cenomanian Turonian oceanic. anoxic event OAE2 Model data comparison, F M Monteiro 1 R D Pancost 2 A Ridgwell 1 and Y Donnadieu3. Received 1 June 2012 revised 19 October 2012 accepted 24 October 2012 published 15 December 2012. 1 The Cenomanian Turonian oceanic anoxic event OAE2 is characterized by large. perturbations in the oxygen and sulfur cycles of the ocean potentially resulting from. changes in oxygen supply via oxygen solubility and ocean circulation and in marine. productivity We assess the relative impact of these mechanisms comparing model. experiments with a new compilation of observations for seafloor dysoxia anoxia and photic. zone euxinia The model employed is an intermediate complexity Earth system model. which accounts for the main ocean dynamics and biogeochemistry of the Cretaceous. climate The impact of higher temperature and marine productivity is evaluated in the. model as a result of higher atmospheric carbon dioxide and oceanic nutrient concentrations. The model shows that temperature is not alone able to reproduce the observed patterns of. oceanic redox changes associated with OAE2 Observations are reproduced in the model. mainly via enhanced marine productivity due to higher nutrient content responsible for. 85 of the change Higher phosphate content could have been sustained by increased. chemical weathering and phosphorus regeneration from anoxic sediments which in turn. induced an enhanced nitrogen nutrient content of the ocean via nitrogen fixation The. model also shows that the presence of seafloor anoxia as suggested by black shale. deposition in the proto North Atlantic Ocean before the event might be the result of the. silled shape and lack of deep water formation of this basin at the Late Cretaceous Overall. our model data comparison shows that OAE2 anoxia was quasi global spreading from 5. of the ocean volume before the event to at least 50 during OAE2. Citation Monteiro F M R D Pancost A Ridgwell and Y Donnadieu 2012 Nutrients as the dominant control on the. spread of anoxia and euxinia across the Cenomanian Turonian oceanic anoxic event OAE2 Model data comparison. Paleoceanography 27 PA4209 doi 10 1029 2012PA002351. 1 Introduction suggesting strong perturbations of the global carbon cycle. Hasegawa 1997 Weissert et al 1998 Jenkyns 2003 2010. 2 Oceanic anoxic events OAEs are severe ocean bio, Other common features of the OAEs include sea level rise. geochemical events common to the Cretaceous period. Erbacher et al 1996 Voigt et al 2006 and changes in. Schlanger and Jenkyns 1976 Schlanger et al 1987 Leckie. stratification and mixing Wilson and Norris 2001 Erbacher. et al 2002 Jenkyns 2010 These events are characterized. et al 2001 Watkins et al 2005 Changes in marine pro. by widespread marine deposition of laminated organic carbon. ductivity and major turnovers in the marine biota are also. rich layers black shales indicating dysoxic if not anoxic. common Jarvis et al 1988 Erbacher and Thurow 1997, conditions at the seafloor Arthur and Sageman 1994 OAEs Kuypers et al 2002 Erba 2004 Browning and Watkins. are associated with positive carbon isotope excursions CIE. 2008 Two of the Cretaceous OAEs are particularly identi. recorded in both marine and continental sedimentary archives. fied as significant globally OAE1a in the early Aptian 120. Myrs and OAE2 at the Cenomanian Turonian boundary,1 93 5 Myrs We focus here on OAE2. School of Geographical Sciences University of Bristol Bristol UK. Organic Geochemistry Unit Bristol Biogeochemistry Research Centre 3 Usually associated with the plateau of maximum car. and The Cabot Institute School of Chemistry University of Bristol Bristol bon isotope excursion Kuypers et al 2002 Tsikos et al. 2004 Erbacher et al 2005 OAE2 is estimated to last. Laboratoire des Sciences du Climat et de l Environnement CNRS about 250 to 700 kyrs Kolonic 2005 Sageman et al 2006. Gif sur Yvette France,Kuroda et al 2007 Seafloor dysoxia anoxia already.
Corresponding author F M Monteiro School of Geographical established in the proto North Atlantic Ocean before OAE2. Sciences University of Bristol University Road Bristol BS8 1SS spread to most of the Atlantic and Indian Oceans Southwest. UK f monteiro bristol ac uk Tethys Sea and possibly in the equatorial Pacific Ocean. 2012 American Geophysical Union All Rights Reserved during the event Schlanger et al 1987 Sinninghe Damst. 0883 8305 12 2012PA002351,PA4209 1 of 17, PA4209 MONTEIRO ET AL DOMINANT CONTROL OF NUTRIENTS ON OAE2 PA4209. and K ster 1998 Tsikos et al 2004 Forster et al 2008 total phosphorus accumulation rates in sediments suggest. Sep lveda et al 2009 Takashima et al 2010 Preceding that the ocean phosphorus content increased right before. OAE2 was an increase in volcanic and hydrothermal marine the OAE2 onset Mort et al 2007 Kraal et al 2010. activity which potentially released large amounts of green With warmer temperatures continental weathering could. house gases into the atmosphere Adams et al 2010 Barclay have intensified and delivered more phosphate to the ocean. et al 2010 Jenkyns 2010 Large igneous provinces started via fluvial inputs Schlanger and Jenkyns 1976 Jones and. to develop in particular at the Caribbean plateau and Mada Jenkyns 2001 Jenkyns 2010 This higher weathering. gascar traps less than 1 Myrs before the onset of OAE2 phosphorus supply is the key mechanism in recent box model. Courtillot and Renne 2003 Snow et al 2005 Kuroda studies to explaining the occurrence and periodicity of the. et al 2007 Turgeon and Creaser 2008 Ando et al OAEs during the Cretaceous Handoh and Lenton 2003. 2009 Reconstructions of atmospheric CO2 suggest high Ozaki et al 2011 an idea that still needs to be tested in a full. concentrations before OAE2 and at its onset in the range of 3D ocean model representation In addition phosphate could. 500 3300 ppmv Bice et al 2006 Barclay et al 2010 have come from sediments once they became anoxic via the. Sinninghe Damst et al 2010 Hay 2011 In parallel preferential phosphorus regeneration relative to carbon Van. reconstructions of sea surface temperature SST indicate Cappellen and Ingall 1994 Bjerrum et al 2006 Tsandev. strong warming with OAE2 where SST increased by about and Slomp 2009 Palastanga et al 2011 Therefore. 5 possibly reaching 33 42 in the mid and tropical latitudes enhanced marine productivity and carbon export could have. Bice et al 2006 Forster et al 2007 Jenkyns 2010 and been an important trigger of OAE2 via elevated phosphate. potentially more than 20 in the Arctic region Jenkyns et al concentrations of the ocean. 2004 Shortly after OAE2 onset pCO2 appears to have 6 Other nutrient cycles also experienced large changes. dropped by about 300 ppmv a 10 50 decline Sinninghe during OAE2 In particular it has been suggested that the. Damst et al 2008 Barclay et al 2010 Jarvis et al fixed nitrogen supply to the ocean increased during the event. 2011 This decline is likely due to the increased carbon due to higher nitrogen fixation Kuypers et al 2004a. burial facilitated by the widespread of anoxia Jenkyns Meyers et al 2009 This is expected because strong rates of. 2010 bacterial mediated denitrification the use of nitrate to. 4 Since the discovery of the widespread deposition of remineralize organic matter must have occurred with the. black shales over 30 years ago Schlanger and Jenkyns spread of dysoxic anoxic environments in the ocean Junium. 1976 the mechanisms responsible for OAE2 and OAEs and Arthur 2007 This would have removed fixed nitrogen. in general remain a topic of intense debate Arthur and from the oceans and favored nitrogen fixation Redfield. Sageman 1994 Meyer and Kump 2008 Jenkyns 2010 1958 Monteiro et al 2011 Higgins et al 2012 As for. Most consider either 1 a reduction in oxygen supply to the iron enhanced hydrothermal activity associated with OAEs. deep ocean allowing higher organic carbon preservation could have provided more iron to the phytoplankton Arthur. Schlanger et al 1987 Arthur and Sageman 1994 or 2 et al 1987 Kolonic 2005 Snow et al 2005 Iron fertil. an increase in marine productivity which provided more ization is however unlikely to be an important trigger of. organic matter to be respired at the expense of oxygen and OAE2 because of a delay between the onsets of the large. other oxidants in the water column and to be buried in the igneous provinces and OAE2 Turgeon and Creaser 2008. sediments Schlanger and Jenkyns 1976 Jenkyns 2010 Ando et al 2009 or the potential of trace metal toxicity for. Both mechanisms oxygen supply and marine productivity marine organisms Erba 2004 Finally nutrient supply to. could potentially explain the change of oceanic redox the ocean surface might have also increased with changes in. observed during OAE2 With increasing temperatures the ocean circulation potentially by increasing the strength of. ocean would have experienced a decrease in oxygen solu upwelling Poulsen et al 2001 Leckie et al 2002 Handoh. bility Arthur and Sageman 1994 Kuypers et al 2002 et al 2003 Junium and Arthur 2007 Overall a range of. and as speculated a slowdown or even stagnation of the changes in ocean biogeochemistry and physics could have. overturning ocean circulation Bralower and Thierstein potentially played a role in either causing or sustaining. 1984 Arthur and Sageman 1994 Warmer temperatures OAE2. could also have increased marine productivity as a result of 7 Here we determine how changes in the oceanic supply. higher phytoplanktonic activity Eppley 1972 Evidence in oxygen including ocean circulation and oxygen solubil. exists for higher marine productivity in the tropics as shown ity and in marine productivity can bring about the observed. from sediment barium content Kuypers et al 2002 and oceanic redox changes associated with OAE2 using the Earth. assemblages of planktic foraminifera and calcareous nan System model GENIE Ridgwell et al 2007 GENIE is a. nofossils Premoli Silva et al 1999 Coccioni and Luciani well designed model for this investigation because it can be. 2005 Hardas and Mutterlose 2007 Recent observations of run for hundreds of thousand years needed to equilibrate the. the North Atlantic Ocean and West Tethys Sea also suggest ocean biogeochemistry and accounts for the main 3 D fea. that marine productivity could have been stimulated by tures of ocean dynamics and biogeochemical cycles of the. increased nutrient supply Kuypers et al 2002 Mort et al Late Cretaceous We compile observations of redox changes. 2007 Jenkyns 2010 of the global ocean combining evidence of seafloor dysoxia. 5 Understanding the mechanism of increased marine anoxia and photic zone euxinia anoxic and free hydrogen. productivity however is not an easy task because of the sulfide before and during OAE2 We then investigate in the. complexity of the marine ecosystem and its interaction model the impacts of paleogeography oxygen supply and. with the nutrient cycles Main limiting nutrients of the marine productivity on oceanic oxygen concentrations for. marine production include phosphate fixed nitrogen different values of atmospheric CO2 and oceanic phosphate. nitrate ammonium and nitrite and iron Evidence from inventory The model results are compared with compiled. PA4209 MONTEIRO ET AL DOMINANT CONTROL OF NUTRIENTS ON OAE2 PA4209. Table 1 Evidence of Seafloor Dysoxia Anoxia Before and During OAE2a. Low Oxygen,Locations Pre OAE2 Evidence References,A Cape Hatteras. DSDP sites 105 603B,Pre Succession of bioturbated green. claystone and laminated black shales,Sinninghe Damst and K ster 1998. Kuypers et al 2004b,TOC 10 OAE2 Laminated black Pancost et al 2004.
shales 3 5 26 TOC absence ofbenthic,foraminifera,B Newfoundland Basin. ODP Site 1276,OAE2 Laminated black shales up to,Sinninghe Damst et al 2010. C Hatteras Abyss,DSDP site 417, OAE2 Laminated black shales 6 TOC Sinninghe Damst and K ster 1998. D Tarfaya Basin Morocco Pre Laminated black shales 2 5 TOC. OAE2 Laminated black shales,Schlanger et al 1987 Sinninghe. Damst and K ster 1998,1 20 TOC Holbourn and Kuhnt 2002.
Kolonic et al 2002 Kuypers,et al 2002 L ning et al 2004. Tsikos et al 2004 Kolonic 2005,Mort et al 2008,E Maracaibo Basin. Pre Succession of laminated marlstone and,chert 10 14 TOC OAE2 Laminated. Schlanger et al 1987 Perez Infante,et al 1996,marlstone 7 11 TOC. F Demerara Rise DSDP site,144 ODP Leg 207,Pre Claystones and laminated black shales.
1 13 TOC OAE2 Laminated black,Sinninghe Damst and K ster 1998. Kuypers et al 2002 Kuroda and, shales 5 32 5 TOC euxinic sediments Ohkouchi 2006 Junium and Arthur. 2007 Arndt et al 2009,Hetzel et al 2009 Meyers,et al 2009. G Cape Verde,DSDP sites 367 368,Pre 9 TOC OAE2 Laminated black. shales 6 5 50 TOC,Sinninghe Damst and K ster 1998,Kuypers et al 2002 L ning et al.
2004 Sinninghe Damst et al,H Angola Basin,DSDP site 530A. Pre Bioturbated red and green claystone,low TOC OAE2 Laminated black. Forster et al 2008,shales 25 TOC low bioturbation, J Eastbourne and Dover UK Pre and OAE2 Bioturbated chalk 0 25 Jarvis et al 1988 Gale et al 2000. TOC benthic foraminifera Tsikos et al 2004, K M nsterland Basin Pre Limestone 1 TOC OAE2 Schlanger et al 1987 Hilbrecht et al. Germany Succession of limestone marlstone and 1992 Ho. conditionsatthe seafloor Arthur and Sageman 1994 OAEs are associated with positive carbon isotope excursions 1958 Monteiro et al 2011 Higgins et al 2012

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