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Submarine Plateau Volcanism and Cretaceous Ocean Anoxic Event 1A: Geochemical Evidence from Aptian Sedimentary Sections

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Submarine Plateau Volcanism and Cretaceous Ocean Anoxic Event 1A: Geochemical Evidence from Aptian Sedimentary Sections AN ABSTRACT OF THE THESIS OF Paul Steven Walczak for the degree of Master of Science in Oceanography presented on May 30, 2006. Title: Submarine Plateau Volcanism and Cretaceous Ocean Anoxic Event 1a: Geochemical Evidence from Aptian Sedimentary Sections. Abstract approved: _____________________________________________________________________ Robert A. Duncan Marine sediments exceptionally rich in organic carbon, known as black shales, occur globally but intermittently in well correlated Cretaceous successions. The presence of black shales indicates that sporadic, ocean-wide interruption of normal respiration of marine organic matter during oxygen-deficient conditions has occurred. Submarine volcanism on a massive scale, related to the construction of ocean plateaus, could be responsible for the abrupt onset and conclusion of these Ocean Anoxic Events (OAEs), via the oxidation of magmatic effluent, the stimulation of increased primary productivity, and the resultant respiration of sinking organic matter. These discrete periods of global ocean anoxia are accompanied by trace metal enrichments that are coincident with magmatic activity and hydrothermal exchange during plateau construction. The link between submarine volcanism associated with the emplacement of the Ontong Java - Manihiki plateau (~122 Ma) and Cretaceous Ocean Anoxic Event 1a is explored in this study. Two marine sedimentary sections, recovered in cores from Deep Sea Drilling Program (DSDP) Site 167 (Magellan Rise) and Site 463 (Mid-Pacific Mountains), were analyzed for a suite of major, minor, and trace elements. Trace element abundance patterns for these locations were compared to similar data from the CISMON core (Belluno Basin, Northern Italy) to determine if a relationship existed between the timing of trace metal anomalies and global biogeochemical events. To account for the variable effects of terrestrial input, trace element data were normalized to Zr and major element data were normalized to Al. Distinct, stratigraphically correlatable peaks could be seen deviating from background levels in the trace element data from the three sites. These anomalous trace metal intervals are related to melt-gas partitioning associated with magmatic degassing and hydrothermal activity resulting from chemical exchange of seawater with cooling plateau rocks. The stratigraphic coincidence of trace metals with other biogeochemical events is consistent with the idea that submarine plateau volcanism, on a massive scale, pushed the global deep ocean into anoxic conditions at discrete intervals of the Cretaceous period. ©Copyright by Paul Steven Walczak May 30, 2006 All Rights Reserved Submarine Plateau Volcanism and Cretaceous Ocean Anoxic Event 1a: Geochemical Evidence from Aptian Sedimentary Sections by Paul Steven Walczak A THESIS submitted to Oregon State University in partial fulfillment of the requirements for the degree of Master of Science Presented May 30, 2006 Commencement June 2007 Master of Science thesis of Paul Steven Walczak presented on May 30, 2006. APPROVED: _____________________________________________________________________ Major Professor, representing Oceanography _____________________________________________________________________ Dean of the College of Oceanic and Atmospheric Sciences _____________________________________________________________________ Dean of the Graduate School I understand that my thesis will become part of the permanent collection of Oregon State University libraries. My signature below authorizes release of my thesis to any reader upon request. _________________________________________________________________ Paul Steven Walczak, Author vii ACKNOWLEDGEMENTS I would like to thank the many people that have made the last several years possible. Foremost, I would like to thank Bob Duncan, my advisor. His support and encouragement have been unwavering, and he has always been on the lookout for opportunities that would interest me and further expand my experiences in the field of oceanography. Another thank you to Randy Keller and Nick Pisias, I don’t feel like my education in oceanography would have been complete without the seagoing experiences that I have had. Thanks also to Gary Klinkhammer and Fred Prahl for serving on my committee, providing great feedback, and teaching enjoyable courses. Without to teachings of Andy Ungerer, Bobbi Conard, and John Huard I would have been very lost in the lab. Additionally, the assistance of Moya and Coreen made my life not only easier, but also more entertaining. Thanks to Dr. Leon Clarke at the University of Wales, Bangor for providing me with samples and data. Further, I would like to thank everyone else who has been a part of my life during the last couple of years. Thanks to my classmates for all of the help, encouragement, and good times. Thanks to Chris for helping me keep my priorities in order. Thanks to Mike, Kurt, Ken, Scott, Garrett, Barney, Aaron, Faron, Wilo, and all of my other friends for keeping me aware of the big picture. Thanks to my parents, well, for everything. I also shouldn’t forget to mention boys up north, for being a constant in my changing world and for giving me a wave or two. Finally, I would like to thank Alison for always being there. viii Support for this project was provided by the American Chemical Society’s Petroleum Research Fund. Without it, none of this would have been possible. ix TABLE OF CONTENTS PAGE Chapter 1: Ocean Plateau Emplacement and Black Shales .......................................... 1 Introduction............................................................................................................... 1 Background: .............................................................................................................. 5 Large Igneous Provinces....................................................................................... 5 Ocean Anoxic Events............................................................................................ 8 Hypotheses for Cretaceous Oceanic Anoxia....................................................... 10 Sedimentary Signatures....................................................................................... 13 Scavenging .......................................................................................................... 19 Diagenesis ........................................................................................................... 21 Cretaceous Metal Anomalies .............................................................................. 22 This Study ............................................................................................................... 23 Chapter 2: Trace Element Abundances in Deep Sea Drilling Project Sites 167 and 463: Their Relationship to the Ontong Java-Manihiki Plateau Emplacement and Ocean Anoxic Event 1a............................................................................................... 24 Methods................................................................................................................... 24 The Ontong Java Plateau......................................................................................... 24 The Manihiki Plateau.............................................................................................. 27 The Magellan Rise .................................................................................................. 28 Sample Acquisition, Site 167.................................................................................. 29 The Mid-Pacific Mountains .................................................................................... 32 Sample Acquisition, Site 463.................................................................................. 33 Sample Processing .................................................................................................. 35 Crushing .............................................................................................................. 35 Powdering ........................................................................................................... 36 Microwave Dissolution....................................................................................... 36 x TABLE OF CONTENTS (CONTINUED) PAGE Microwave Evaporation...................................................................................... 37 Microwave Cleaning........................................................................................... 38 Sample Analyses ..................................................................................................... 38 Trace and Minor Elements.................................................................................. 38 Major Elements ................................................................................................... 44 Results..................................................................................................................... 45 Site 167 ............................................................................................................... 45 Site 463 ............................................................................................................... 46 Discussion ............................................................................................................... 49 Degassing, Hydrothermalism, and Trace Metals ................................................ 58 Residence Time, Cretaceous Circulation, and Location ....................................
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