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The Effects of Sea Level Change on the Molecular and Isotopic University of Massachusetts Amherst ScholarWorks@UMass Amherst Masters Theses 1911 - February 2014 January 2008 The ffecE ts of Sea Level Change on the Molecular and Isotopic Composition of Sediments in the Cretaceous Western Interior Seaway: Oceanic Anoxic Event 3, Mesa Verde, Co, Usa Jeff alS acup University of Massachusetts Amherst Follow this and additional works at: https://scholarworks.umass.edu/theses Salacup, Jeff, "The Effects of Sea Level Change on the Molecular and Isotopic Composition of Sediments in the Cretaceous Western Interior Seaway: Oceanic Anoxic Event 3, Mesa Verde, Co, Usa" (2008). Masters Theses 1911 - February 2014. 195. Retrieved from https://scholarworks.umass.edu/theses/195 This thesis is brought to you for free and open access by ScholarWorks@UMass Amherst. It has been accepted for inclusion in Masters Theses 1911 - February 2014 by an authorized administrator of ScholarWorks@UMass Amherst. For more information, please contact [email protected]. THE EFFECTS OF SEA LEVEL CHANGE ON THE MOLECULAR AND ISOTOPIC COMPOSITION OF SEDIMENTS IN THE CRETACEOUS WESTERN INTERIOR SEAWAY: OCEANIC ANOXIC EVENT 3, MESA VERDE, CO, USA A Thesis Presented by JEFFREY M. SALACUP Submitted to the Graduate School of the University of Massachusetts Amherst in partial fulfillment of the requirements for the degree of MASTER OF SCIENCE September 2008 Department of Geosciecnes THE EFFECTS OF SEA LEVEL CHANGE ON THE MOLECULAR AND ISOTOPIC COMPOSITION OF SEDIMENTS IN THE CRETACEOUS WESTERN INTERIOR SEAWAY: OCEANIC ANOXIC EVENT 3, MESA VERDE, CO, USA A Thesis Presented by JEFFREY M. SALACUP Approved as to style and content by: ____________________________________ Steven T. Petsch, Chair ____________________________________ R. Mark Leckie, Member ____________________________________ Stephen J. Burns, Member ____________________________________ Robert DeConto, Member _______________________________________ Laurie Brown, Department Head Department of Geoscience ABSTRACT THE EFFECTS OF SEA LEVEL CHANGE ON THE MOLECULAR AND ISOTOPIC COMPOSITION OF SEDIMENTS IN THE CRETACEOUS WESTERN INTERIOR SEAWAY: OCEANIC ANOXIC EVENT 3, MESA VERDE, CO, USA SEPTEMBER 2008 JEFFREY SALACUP, B.S., UNIVERSITY OF MASSACHUSETTS AMHERST Directed by: Associate Professor Steven T. Petsch Cretaceous Oceanic Anoxic Events (OAEs) represent periods of enhanced burial of organic matter in black shale in marine, continental margin, and epicontinental settings around the globe. Compared to other OAEs, comparatively little is known about the last of these widespread events, OAE 3 (Coniacian-Santonian). The Mancos Shale at Mesa Verde National Park is an Upper Cretaceous (Cenomanian-Campanian) formation containing marine sediments of the second-order Niobrara cyclothem and associated third-order transgressive-regressive events (T1-T4). The Coniancian-Santonian Niobrara interval is characterized as dark-gray, moderately to well laminated, calcareous shale and mudstone. Synthesis of new high-resolution bulk chemostratigraphy and biomarker analyses with the preexisting geochemical, lithological, and biostratigraphical framework suggest a temporally protracted oxygen minimum zone was largely responsible for the preservation of large quantities of organic matter contained in these sediments. 15 Additionally, C/N and δ Nbulk values imply denitrification and nitrogen fixation were both important metabolic processes during periods when surface water nutrient profiles may have differed much from those of the modern ocean. iii TABLE OF CONTENTS Page ABSTRACT.......................................................................................................................iii LIST OF TABLES.............................................................................................................vii LIST OF FIGURES..........................................................................................................viii CHAPTER 1. CRETACEOUS OCEANIC ANOXIC EVENTS AND SEA LEVEL…………………1 1.1 Cretaceous Oceanic Anoxic Events…………………………………………...1 1.1.1 Controls on Organic Matter Accumulation and Utility in Paleo- reconstructions…………………………………………………….3 1.1.2 Oceanic Anoxic Event 1a…………………………………………....7 1.1.3 Oceanic Anoxic Event 1b…………………………………………...8 1.1.4 Oceanic Anoxic Event 1c and 1d………………………...………....9 1.1.5 Oceanic Anoxic Event 2………………………………………….....9 1.1.6 Oceanic Anoxic Event 3…………………………………………...11 1.2 High Global Sea Level and the Late-Cretaceous Western Interior Seaway…13 1.2.1 Depositional Patters and Cyclicity in the KWIS…………………...16 1.2.2 Paleoceanography of the KWIS……………………………………16 1.2.3 The San Juan Basin: Late-Cretaceous Depocenter………………...19 1.2.4 The Niobrara Cyclothem and Mesa Verde………………………...20 2. SEA LEVEL, OXYGEN STRESS, AND WATER COLUMN ECOLOGY DURING OCEANIC ANOXIC EVENT 3…………………………………………………25 2.1 Hypothesis…………………………………………………………………....26 2.1.1 Objectives.........................................................................................26 2.2 Methods............................................................................................................27 2.2.1 Sampling, Biostratigraphy, and Age……………………………….27 2.2.2 Bulk Analyses……………………………………………………...29 2.2.3 Molecular Analyses………………………………………………..31 iv 2.2.4 Consideration of Maturity and Biodegradation……………………32 2.2.4.1 Maturity…………………………………………………..33 2.2.4.2 Biodegradation…………………………………………...35 2.2.5 Biomarker Utility in Environmental Reconstruction………………35 2.3 Results………………………………………………………………………..38 2.3.1 Bulk Characteristics………………………………………………..38 2.3.2 Molecular Characteristics……………………………………….....44 2.3.2.1 Compound Distribution.....................................................44 2.3.2.2 Sample Maturity and Biodegradation................................44 2.3.2.3 Saturated Hydrocarbons.....................................................46 2.3.2.4 Aryl-Isoprenoids................................................................47 2.4 Discussion........................................................................................................48 2.4.1 Correlation of Coniacian-Santonian Sea Level Change at Mesa Verde..............................................................................................48 2.4.2 Terrestrial vs. Algal Ratio: Source Indicator or Diagenetic Imprint? .........................................................................................51 13 2.4.3 δ Ccarb: Timing of Oceanic Anoxic Event 3 at Mesa Verde............54 2.4.4 Sediment Fabric................................................................................56 2.4.5 Gamma Ray and Th/U Ratios...........................................................57 2.4.6 C/N Ratios and Denitrification.........................................................59 15 2.4.7 δ Nbulk and Nitrogen Fixation.........................................................62 2.4.8 Photic Zone Euxinia..........................................................................64 2.4.9 Organic Matter..................................................................................65 13 2.4.10 δ COM: A Mixing Model................................................................66 2.5 Conclusions......................................................................................................70 3. FURTHER WORK........................................................................................................73 APPENDICES 1: CORRELATIVE X/Y PLOTS......................................................................................75 2: BIOMARKER CONCENTRATIONS........................................................................76 3: REPRESENTATIVE CHROMATOGRAMS (A) AND MASS FRAGMENTATION PATTERS (B) OF N-ALKANES (M/Z 57), HOPANES (M/Z 191), AND STERANES (M/Z 217).........................................................................................78 v REFERENCES..................................................................................................................81 vi LIST OF TABLES 2.1 Biomarker Interpretation..............................................................................................33 2.2 Bulk Geochemical Interpretation.................................................................................36 2.3 Supporting Data...........................................................................................................40 2.4 Bulk Geochemical Data...............................................................................................41 2.5 Biomarker Results........................................................................................................45 vii LIST OF FIGURES 1.1 Geographic occurrence of the various Oceanic Anoxic Events and their depositional facies. Added in red is our section at Mesa Verde during OAE 3. Adapted from Schlanger, 1976........................................................................................................4 1.2 The mid-Cretaceous record of major black shales and OAEs and the associated carbon isotopic record (Erbacher et al., 1996; Bralower et al., 1999), changing global sea level (Haq et al., 1988), and seawater chemistry (Bralower et al., 1997). Short-term sea level changes are shown as the dark shaded line, and the long-term record of sea level is shown with the thick solid line (adapted from Haq et al. (1988)). Initiation of increased spreading rates drove the long-term (Albian- Turonian) rise of global sea level. (From Leckie, 2002).........................................5 1.3 Locations of organic carbon-rich
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