Refining pedogenic carbonate proxies for improved reconstructions of past terrestrial environmental conditions by Timothy Michael Gallagher A dissertation submitted in partial fulfillment of the requirements for the degree of Doctor of Philosophy (Geology) in the University of Michigan 2016 Doctoral Committee: Associate Professor Nathan D. Sheldon, Chair Assistant Professor Vincent Denef Associate Professor Gregory J. Dick Professor Kyger C. Lohmann © Timothy M. Gallagher 2016 Acknowledgements First, I would like to thank my advisor, Nathan Sheldon, for taking me on as a student, giving me the opportunity to pursue a wide variety of questions during my PhD, and providing helpful advice through it all. I would also like to thank my committee members for providing constructive feedback and supporting an ever-adjusting dissertation plan. Thanks to my coauthors, Mike Hren, Jeff Mauk, Sierra Petersen, Nur Gueneli, and Jochen Brocks, for their helpful comments and assistance with data collection. Thanks also to all of the lab-mates who listened and helped me work through my ideas (even if the slides were completely blank). Thanks (and sorry) to Sara Leon who crushed so, so many rocks and filled innumerable tin capsules without ever uttering a word of complaint (to my face). Thanks to Lora Wingate for teaching me a lot about machines and always letting me borrow equipment and consumables when I was in a bind. And thanks to all the friends and fellow graduate students in the department who helped make the past five years enjoyable. This work would not have been possible without the fellowships from the National Science Foundation Graduate Research Fellowship Program and the Department of Earth and Environmental Sciences. My dissertation research was supported by grants from American Philosophical Society, the American Association of Petroleum Geologists Foundation, the Geological Society of America, the Rackham Graduate School, and the Scott Turner Fund. I would like to thank my parents and sister for all the love and support they provided through the years. Finally and most of all, thanks to Allie for talking me into this whole PhD and ii international adventure we have been the past eight years (granted it didn’t take much convincing) and always being there with me every step of the way. iii Table of Contents Acknowledgements ....................................................................................................................... ii List of Tables ................................................................................................................................. v List of Figures ............................................................................................................................... vi List of Appendices ..................................................................................................................... viii Abstract ........................................................................................................................................ ix Chapter 1. Introduction ................................................................................................................... 1 Chapter 2. Combining soil water balance and clumped isotopes to understand the nature and timing of pedogenic carbonate formation ........................................................... 12 Chapter 3. The effect of seasonally fluctuating soil environments on temperature reconstructions from paleosols ................................................................................... 56 Chapter 4. Constraining the thermal history of the North American Midcontinent Rift System using carbonate clumped isotopes and organic thermal maturity indices ......83 Chapter 5. Conclusions .............................................................................................................. 119 Appendices ................................................................................................................................. 127 iv List of Tables Table 2.1 Site Information .................................................................................................... 17 Table 2.2 Geochemical results from pedogenic carbonate ................................................... 22 Table 3.1 Comparison to clumped isotope data .................................................................... 77 Table 4.1 Sample type and locality ...................................................................................... 93 Table 4.2 Clumped isotope Geochemistry results ............................................................... 96 Table 4.3 Organic thermal maturity data ............................................................................. 99 Table A.1 Sites and corresponding climate station information ......................................... 127 Table A.2 Soil thermal properties ....................................................................................... 127 Table A.3 Summary of evapotranspiration and soil water balance calculations ................ 128 Table A.4 Raw Clumped Isotope Data ................................................................................ 131 Table A.5 Clumped Isotope Data – Samples in the Absolute Reference Frame ................ 135 Table A.6 Run intervals and corresponding transfer function values used ........................ 139 Table A.7 Corrected stable isotope data and δ18O soil water calculations ......................... 139 Table B.1 SCAN stations, climate normal stations, and excluded data ............................. 141 Table B.2 Average maximum and minimum monthly air and soil temperatures ............... 145 Table B.3 Driest 30-day intervals and corresponding soil temperatures ............................. 149 Table C.1 Raw Clumped Isotope Data 1 of 2 ..................................................................... 153 Table C.2 Raw Clumped Isotope Data 2 of 2 ..................................................................... 157 v List of Figures Figure 2.1 Map showing sample localities for pedogenic carbonate nodules samples ......... 16 Figure 2.2 Observed and modeled temperatures for the Eros and Adams Ranch sites ......... 24 Figure 2.3 Observed soil moisture data and water balance model results for the Eros and Adams Ranch sites ......................................................................................... 25 Figure 2.4 Summary of soil water balance calculations for all sites ..................................... 26 Figure 2.5 Average clumped isotope temperatures plotted against mean annual air temperature for each site ....................................................................................... 30 Figure 2.6 Monthly precipitation totals, modelled soil temperatures, and clumped isotope temperatures for all sites .......................................................................... 36 Figure 2.7 Calculated δ18O values of the soil water vs. OIPC-derived δ18O values of precipitation ......................................................................................................... 41 Figure 3.1 Air temperature seasonality compared to soil temperature seasonality ............... 64 Figure 3.2 Minimum monthly air temperatures compared to the deviation of soil temperatures from predicted values at depth ...................................................... 65 Figure 3.3 Binned site distribution of the difference between mean annual soil temperature and mean annual air temperature ..................................................... 68 Figure 3.4 Binned site distribution of the number of months where average soil temperature exceeds mean annual air temperature .............................................. 69 Figure 3.5 Seasonal timing of soil moisture scenarios that considered favorable for pedogenic carbonate formation ............................................................................. 71 Figure 3.6 Distribution of the temperature biases relative to mean annual air temperature during the corresponding soil moisture scenario ............................. 72 Figure 3.7 Spatial distribution of soil temperatures relative to mean annual air temperature during the driest 30-day interval ...................................................... 74 vi Figure 3.8 Spatial distribution of soil temperatures relative to mean annual air temperature during the larges 30-day decline in soil moisture ............................ 75 Figure 4.1 Geologic map of surface exposures of the Midcontinent Rift System (MRS) units in the western Lake Superior region ............................................... 85 Figure 4.2 Stratigraphic units of the Keweenaw Supergroup in Minnesota, Wisconsin, and Michigan ....................................................................................................... 87 Figure 4.3 Clumped isotope temperatures results for calcite samples from the Midcontinent Rift ................................................................................................. 98 Figure 4.4 Modeled solid-state reordering of clumped isotope values under different burial scenarios .................................................................................................. 106 Figure 4.5 Calculated δ18O values of the precipitating fluids ............................................. 109 Figure A.1 Additional plots of calculated δ18O values vs. OIPC-derived δ18O values of precipitation ......................................................................................................