Carbon cycle changes during the Triassic-Jurassic transition Micha Ruhl Micha Ruhl Palaeoecology Institute of Environmental Biology Laboratory of Palaeobotany and Palynology Utrecht University Budapestlaan 4 3584 CD Utrecht the Netherlands ISBN: 978-90-393-5270-0 NSG publication number: 20100126 LPP Contribution Series 28 Cover-design: Micha Ruhl Printed by GVO drukkers & vormgevers B.V. | Ponsen & Looijen, Ede Carbon cycle changes during the Triassic-Jurassic transition Koolstofkringloop veranderingen gedurende de Trias-Jura overgang (met een samenvatting in het Nederlands) Proefschrift ter verkrijging van de graad van doctor aan de Universiteit Utrecht op gezag van de rector magnificus, prof. dr. J.C. Stoof, ingevolge het besluit van het college voor promoties in het openbaar te verdedigen op dinsdag 26 januari 2010 des ochtends te 10.30 uur door Micha Ruhl geboren op 16 april 1980 te Horn Promotor: Prof. dr. A.F. Lotter Co-promotor: Dr. W.M. Kürschner The research reported in this thesis was funded by the High Potential program of Utrecht University. The printing of this thesis was financially supported by LAMERS TOOLING BV. Contents General Introduction and Synopsis 9 Chapter 1 Triassic-Jurassic organic carbon isotope stratigraphy of 15 key sections in the western Tethys realm (Austria) Ruhl, M., Kürschner, W.M., Krystyn, L. Earth and Planetary Science Letters 281 (2009) 169-187 Chapter 2 Climate change driven black shale deposition during the 31 end-Triassic in the western Tethys Bonis, N.R., Ruhl, M., Kürschner, W.M. Palaeogeography, Palaeoclimatology, Palaeoecology (in press) Chapter 3 Sedimentary organic matter characterization of the 47 Triassic-Jurassic boundary GSSP at Kuhjoch (Austria) Ruhl, M., Veld, H., Kürschner, W.M. Earth and Planetary Science Letters (in review) Chapter 4 Atmospheric methane injection caused end-Triassic mass 63 extinction Ruhl, M., Bonis, N.R., Reichart, G.-J., Sinninghe Damsté, J.S., Kürschner, W.M. (submitted) Chapter 5 Astronomical constraints on the duration of the early 75 Jurassic Hettangian stage and recovery rates following the end-Triassic mass extinction (St. Audrie’s Bay/East Quantoxhead, UK) Ruhl, M., Deenen, M.H.L., Abels, H.A., Bonis, N.R., Krijgsman, W., Kürschner, W.M. Earth and Planetary Science Letters (in review) Chapter 6 Multiple late Triassic carbon cycle perturbation observed 97 in continental and marine C-isotope records from the western Tethys (Austria) and NW European sections (UK and Germany) Ruhl, M., Kürschner, W.M. (submitted) References 107 General Introduction and Synopsis in Dutch 121 Acknowledgements 129 Curriculum Vitae 133 Publications 137 Appendices 138 General Introduction The cumulative anthropogenic release of up to 5000 Gt of carbon to the atmosphere and oceans in the coming centuries, may have a large influence on earths climate and biosphere (Caldeira and Wickett, 2003; Allen et al., 2009). The magnitude of projected future climate changes depends on often poorly constrained feedback mechanisms. Understanding boundary conditions for climate change in response to anthropogenic greenhouse gas emissions is necessary to ensure a relatively stable state of the Earth system (Rockström et al., 2009). Geological history is marked by multiple (major) carbon cycle perturbations, often in concurrence with climate change and biodiversity loss. In the past several thousands of years, mankind experienced only relatively minor environmental changes. Larger changes in climate did occur in the course of human evolution, during the Pleistocene (Hays et al., 1976). Time intervals with similar carbon emissions as today may however have only occurred tens to hundreds of million years ago. Understanding the potential causal relation between former climate change and massive carbon release, may allow for better predictions of future environmental changes. Studying these time intervals is of particular importance for understanding the mechanisms behind changes in climate and the carbon cycle and their effects on ecosystem evolution, species composition and the rate of biotic origination. Causes of extinction events have varied, but understanding of the underlying mechanisms may provide vital insight in the causes and effects of current (man-induced) biodiversity loss (Sala et al., 2000). The study presented in this thesis is part of a multi-proxy project “Earth’s and Life’s History: From Core To Biosphere (CoBi)”, aiming to better constrain the causes, relative timing and mutual relation between changes in terrestrial and marine ecosystems and the global carbon cycle during the Triassic-Jurassic transition and especially the end- Triassic mass extinction interval (~201.5 Ma; Schaltegger et al., 2008). The late Triassic has often been regarded as one of five major mass extinctions of the Phanerozoic (Raup and Sepkoski, 1982; Benton, 1995). In contrast to the sudden and catastrophic extinction event at the Cretaceous-Paleogene boundary, which is ascribed to a celestial bolide impact (Smit and Hertogen, 1980; Smit and ten Kate, 1982), late Triassic extinctions extended over several million years (Tanner et al., 2004; Kiessling et al., 2007; Kürschner and Herngreen, in press). Extinctions culminated in the end-Triassic, with marine and continental extinctions (e.g. ammonites (Guex et al., 2004), bivalves (McRoberts and Newton, 1995), radiolaria (Ward et al., 2001) and Theropod dinosaurs (Olsen et al., 2002)) and marine and terrestrial assemblage changes (e.g. dinoflagellates and foraminifera (Hesselbo et al., 9 General Introduction and Synopsis 2002) and vegetation (Kürschner et al., 2007; Bonis et al., 2009, McElwain et al., 2009)). Although the end-Triassic mass extinction provides an eminent case history of global biosphere turnover, current concepts differ with respect to its cause (celestial versus terrestrial). A bolide impact was suggested after the discovery of an iridium anomaly in co-occurrence with a fern spike (Olsen et al., 2002). Supportive evidence such as shocked quartz grains and impact structures is however lacking (Tanner et al., 2004). The onset of massive volcanism and large-scale flood basalt outflow is often tentatively related to mass extinction intervals (Wignall, 2001; Courtillot and Renne, 2003). Large Igneous Province (LIP) emplacement in the Central Atlantic Magmatic Province (CAMP), likely related to the initial break up of Pangea (Olsen, 1997), possibly resulted in major influxes of CO2 and SO2 and consequent greenhouse warming, poisoning of ecosystems and marine anoxia (Beerling and Berner, 2002; Wignall et al., 2007; van de Schootbrugge et al., 2009). The timing and duration of CAMP eruptions are however still controversial (Marzoli et al., 2004; Marzoli et al., 2008; Whiteside et al., 2007; Whiteside et al., 2008). Fundamental questions about causes and causal relationships between end-Triassic global biotic turnovers, global changes in biogeochemical cycles and climate change are still debated. GSSP for the base of the Jurassic System In contrast to pre- and succeeding mass extinction events, attention for the end-Triassic extinction interval increased only more recently, when more boundary sections were discovered and available for study. The Triassic-Jurassic boundary is therefore one of the very last period boundaries to be allocated by the International Commission on Stratigraphy, to a Global boundary Stratotype Section and Point (GSSP) for the base of the Jurassic system. In the past few years and during the course of this research there has been ongoing discussion on appropriate criteria for the marker of the base of the Jurassic. A distinct negative Carbon Isotope Excursion (CIE) has now been extensively documented in the Eiberg Basin (chapter 1) and elsewhere and it can be regarded as a global phenomenon (chapter 4). It coincides with the extinction interval and was one of the proposed boundary markers. However, the first occurrence (FO) of the ammonite Psiloceras spelae was also proposed (Hillebrandt et al., 2007) and chosen as marker for the base of the Jurassic. Two subspecies of this ammonite, P. spelae spelae and P. spelae tirolicum (Hillebrandt and Krystyn, 2009), have their FO more or less simultaneously in New York Canyon (Panthalassic Ocean) and the Eiberg Basin (western Tethys Ocean), respectively. The Kuhjoch section in the Eiberg Basin was proposed (Hillebrandt et al., 2007) and ultimately accepted as GSSP for the base of the Jurassic. This section has been extensively studied during the course of this project (Bonis et al., 2009; Ruhl et al., 2009) and some of the data are discussed in chapters 1, 2, 3 and 4 of this thesis. 10 General Introduction and Synopsis Synopsis The end-Triassic extinction interval provides an eminent case-study for understanding potential causal relationships between carbon release, climate change and biodiversity loss/ecosystem changes. The study presented in this thesis mainly focuses on global carbon cycle changes at the Triassic-Jurassic transition. These reflect changes in flux sizes between the exogenic exchangeable carbon reservoirs (e.g. atmosphere, oceans, standing biota). In steady-state, the exogenic carbon pool is marked by constant flux and reservoir sizes and a fixed carbon retention time for each reservoir. Potential changes in these parameters may alter the relative abundance of 13C and 12C stable isotopes in each reservoir, which is reflected by marked perturbations in C-isotope proxy records. Carbon can also be transferred to the exogenic carbon pool from external reservoirs