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An Investigation of Changing Wind Energy on The AN INVESTIGATION OF CHANGING WIND ENERGY ON THE EVOLUTION OF COPANOBAY, TEXAS By BENJAMIN TAYLOR TROIANI Bachelor of Science in Geology Wichita State University Wichita, Kansas 2006 Submitted to the Faculty of the Graduate College of the Oklahoma State University in partial fulfillment of the requirements for the Degree of MASTER OF SCIENCE May, 2010 AN INVESTIGATION OF CHANGING WIND ENERGY ON THE EVOLUTION OF COPANO BAY, TEXAS Thesis Approved: Dr. Alexander Simms Thesis Adviser Dr. Estella Atekwana Dr. James Puckette Dr. A. Gordon Emslie Dean of the Graduate College ii ACKNOWLEDGMENTS This thesis exists as a result of the support provided by Boone Pickens School of Geology, Oklahoma State University. Without their financial support and use of their facilities, this thesis would not be possible. My advisor Dr. Alexander R. Simms deserves special credit. I feel he went above and beyond his duties as an advisor and was always there for guidance, support, and encouragement. Without his service, I would have never finished. I would also I like to thank the other members of my committee, Dr. James Puckette and Dr. Estella Atekwana for providing valuable input into my research. I would like to thank Dr. Tim Dellapenna and Erin Weaver at Texas A&M at Galveston for providing the seismic data from Copano Bay and use of their facilities to help interpret the seismic data. I am very grateful for Yusuke Yokoyama from the University of Tokyo, Japan for providing radiocarbon ages. I would also like to thank Tyler Treece and Derk Federko for their help in the field and Lauren Miller for her help in the lab. This research was funded by Gulf Coast Section of Economic Paleontologist and Mineralogists (GCSSEPM) Ed Picou fellowship for graduate students and the Petroleum Research Fund of the America Chemical Society. iv TABLE OF CONTENTS Chapter Page I. INTRODUCTION ......................................................................................................1 Hypothesis................................................................................................................4 II. STUDY AREA ..........................................................................................................6 Holocene Sea-Level History of the U.S. Gulf Coast ...............................................8 Holocene Climate History Texas .............................................................................9 III. METHODOLOGY ................................................................................................12 Core Description ....................................................................................................12 Surface Samples .....................................................................................................14 Seismic Data Interpretation....................................................................................15 Chronostratigraphy ................................................................................................15 Paleogeographic Map.............................................................................................16 IV. RESULTS ..............................................................................................................17 Sedimentology ......................................................................................................17 Grain-size analysis .................................................................................................23 Seismic ...................................................................................................................23 Events .....................................................................................................................27 Last Glacial Maximum unconformity Structure Map ............................................28 Radiocarbon dates ..................................................................................................30 V. DISCUSSION ........................................................................................................32 Bay Evolution ........................................................................................................32 Grain Size Modes ...................................................................................................38 Reconstructing Paleo-Winds ..................................................................................41 Grain Size Trends ..................................................................................................42 Could wind have been a mechanism for a flooding event? ...................................53 v VI. CONCLUSION......................................................................................................54 REFERENCES ............................................................................................................55 ABSTRACT .................................................................................................................61 vi LIST OF TABLES Table Page 1. Radiocarbon dates collected for this study .........................................................31 2. Placement of modes ............................................................................................43 vii LIST OF FIGURES Figure Page 1. Showing a linear relationship between fetch and depth ........................................3 2. Copano Bay in relation to the Gulf of Mexico and climate belts .........................5 3. Sea-level indices for the Gulf of Mexico ...........................................................10 4. The location of seismic lines and cores within Copano Bay .............................13 5. Core description results.......................................................................................18 6. Facies diagram of Copano Bay ...........................................................................19 7. A-F Photographs of sedimentary facies ..............................................................20 8. Map of Copano Bay showing locations of GSFC environments ........................24 9. Seismic line 141 ..................................................................................................25 10. Seismic line 43 ....................................................................................................26 11. Last Glacial Maximum unconformity Structure Map .........................................29 12. A-E paleogeography of Copano Bay ............................................................ 33-34 13. A typical grain-size frequency curve for Copano Bay........................................40 14. Core description, Grain-size moment mean graph, Ratio between the magnitudes of mode 2 and 3 graph and Occurrences and magnitude of mode 4 ...................45 15. Dimensionless wind strength proxy and Toomey et al (1993) ratio of Notiosorex to Notiosorex and Cryptotis ..............................................................47 16. Correlation of wind strength proxy and Toomey et al (1993) graph ..................50 17. Linear compaction model ...................................................................................52 viii CHAPTER I INTRODUCTION Estuaries are complex, dynamic, and sensitive not only to changes in sea-level rise but also to other factors including changes in sediment supply and climate (Allen, 1971; Shideler, 1984; Dalrymple et al., 1992; Rodriguez et al., 2005; Anderson et al., 2008; Maddox et al., 2008; Milliken et al., 2008b; Simms et al., 2008). One very important and often overlooked aspect of climate change is the impact that changing wind energy has on bay evolution. Shideler (1984) determined that wind is the dominant forcing agent regulating estuarine sedimentary processes along the Texas Gulf coast. Wind generated waves and currents, i.e. bottom wave orbitals, have the ability to resuspend bay-floor sediments in the water-column and a direct relationship exists between mean wind speed and sediment concentration in the water-column (Shideler, 1984). Bay-floor sediment concentration in the water column is a function of maximum bottom orbital velocity, which can be expressed by Lamp (1945) in the following equation. U=H π/((TSinh)((2 πh)/ λ))) Eq. (1) 1 Where U=the maxium bottom orbital velocity, H=the wave height, T=the wave period , λ=the wavelength, and h=water depth at the point of consideration. These wave parameters are controlled by the fetch of a bay and wind speed. Shideler (1984) noticed that the resuspended bay-flood sediments within Nueces Bay, Texas were being exported out of the bay by strong northerly winds and the astronomical ebb tide. As a result of the resuspension of bay-flood sediments, estuarine systems are flushed of fine-grain bay-floor sediments. Price (1947) and Nichols (1989) noticed that sedimentation and accumulation rates along with lagoonal surface area (ie. fetch) are in equilibrium with wave energy dissipation. This relationship holds true for the bays of the Texas coast (Figure 1). Thus, changes in wind strength and/or fetch area will disrupt this equilibrium and cause a change in the accumulation rate of sediments within estuaries. In most modern lagoons, Nichols (1989) noticed that sediment accumulation rates equal the rate of relative sea-level rise. The objective of this investigation is to study the role wind energy had on the evolution of Copano Bay over the last 10 k.a., a time of known variable sea-level rise, sediment supply, and climate (Allen, 1971; Shideler, 1984; Toomey et al., 1993; Tornqvist et
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