Geologic Characterization of Ladon Valles, Mars and the Surrounding Area a Thesis Presented to the Faculty of the College Of
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Geologic Characterization of Ladon Valles, Mars and the Surrounding Area A thesis presented to the faculty of the College of Arts and Sciences of Ohio University In partial fulfillment of the requirements for the degree Master of Science Doug C. Wolfinger May 2014 © 2014 Doug C. Wolfinger. All Rights Reserved. 2 This thesis titled Geologic Characterization of Ladon Valles, Mars and the Surrounding Area by DOUG C. WOLFINGER has been approved for the Department of Geological Sciences and the College of Arts and Sciences by Keith M. Milam Associate Professor of Geological Sciences Robert Frank Dean, College of Arts and Sciences 3 Abstract WOLFINGER, DOUG C., M.S., May 2014, Geological Sciences Geologic Characterization of Ladon Valles, Mars and the Surrounding Area Director of Thesis: Keith A. Milam Ladon Valles and Ladon Basin, Mars (Ladon study area), are in the path of what is potentially the solar system’s longest fluvial system. In this study, the geology of the Ladon study area is analyzed in an attempt to reconstruct the geologic record for the Uzboi-Ladon-Morava drainage system and the Margaritifer Terra region of Mars. An integral part of this reconstruction has been to determine the geologic processes that formed Ladon Valles. Although previous workers have referred to Ladon Valles as an “outflow channel system,” no formal geologic characterization has led to that determination. Only precursory discharge estimates have been produced for Ladon Valles and there are discrepancies regarding the timing and duration of erosional and depositional events in the Ladon study area. High resolution orbital data (Mars Global Surveyor, Mars Odyssey, Mars Reconnaissance Orbiter and Mars Express), has been used to assess the types of channel that is Ladon Valles’s middle channel (main channel), as well as its outer channels, and their discharge as well as establish the timing and duration of events in the Ladon study area through crater retention dating. With these constraints, discharge rates have been estimated. Ladon Valles landforms are consistent with both glacially carved and outflow channels, with the exception of streamlined islands, which is indicative exclusively of outflow channels. With the exception of the final stage, maximum estimates of the discharge values through the main channel are all 4 at least 106 m3 s-1, placing them within the range for outflow channels. The final stage through the main channel was less powerful and is most accurately categorized with valley networks in terms of discharge magnitude. Discharge results for Ladon Valles’s anastomosing channels are considerably weaker, some falling within the range for valley networks, and others within that for outflow channels. Water flowed abundantly through the Early-to-Mid-Noachian and began tapering off in the Late Noachian. An Early Hesperian flow was possible but fluvial action more likely came to an end by the Late Noachian. 5 Acknowledgments My sincere thanks and appreciation go to my advisor, Dr. Keith Milam, for his mentorship, and to my committee members, Dr. Doug Green, and Dr. Greg Springer, for their assistance in building this graduate thesis. I would also like to extend my gratitude to Dr. Caleb Fassett, of Mount Holyoke College, for his advice. 6 Table of Contents Page Abstract ................................................................................................................................3 Acknowledgments................................................................................................................5 List of Tables .......................................................................................................................7 List of Figures ......................................................................................................................8 1: Introduction…………………………………………………………………………... 10 Geologic Setting………………………………………………………………… 10 Is Ladon Valles an Outflow System ......................................................................11 Timing and Duration of Events in Ladon Valles ...................................................16 2: Questions .......................................................................................................................19 3: Methods .........................................................................................................................20 Is Ladon Valles an Outflow Channel? ...................................................................21 Estimating Discharge in Ladon Valles ..................................................................25 Timing and Duration of Flow in Ladon Valles ......................................................31 4: Results ............................................................................................................................35 Is Ladon and Outflow Channel ..............................................................................35 Timing and Duration of Events..............................................................................61 5: Discussion ......................................................................................................................66 Landforms ..............................................................................................................66 Discharge ...............................................................................................................67 Timing and Duration of Events Outside Ladon Valles ..........................................75 Timing and Duration of Ladon Valles Events .......................................................77 6: Summary ........................................................................................................................92 References ..........................................................................................................................93 Appendix A Images Corresponding to Unit Descriptions in Table 3........................................ 99 Images Corresponding to Unit Descriptions in Table 4...................................... 108 Appendix B Plan Views of Cross-sectional Profiles in Figure 15. ..........................................117 7 List of Tables Tables Page 1. Data Specifications…………………………………………………………….. 20 2. List of Geomorphic Features Found on Mars………………………………….. 24 3. Descriptions of the Geologic Units Outside the Main Channel……………….. 39 4. Descriptions of the Geologic Units Within the Main Channel…………….…... 45 5. Values for Sinuosity and Aspect Ratio………………………………………… 51 6. Discharge Estimates for Ladon Valles………………………………………… 55 7. Ages of Proposed Geologic Units Outside the Main Channel………………… 62 8. Ages of Formations of the Ladon Valles Group………………………………. 64 9. Floor Elevation Ranges of Ladon Valles’s Anastomosing Channels…………. 78 10. Comparisons of Mid-to-Early Noachian Main Channel Discharge Estimates.. 82 8 List of Figures Figures Page 1. MOLA Elevation Map……………………………………………………....... 12 2. Schematic of Margaritifer Terra Flow Directions…………………………….. 13 3. Martian Terrain Mapped by Period of Formation…………………………….. 14 4. Comparison of Discharge Estimates………….……………………………….. 15 5. Timing of Major Events in the Ladon Study Area……………………………. 17 6. Example of a Profile Line Used in a Discharge Calculation………………….. 26 7. Floor of the Main Channel…………………………………………………….. 29 8. Martian Crater-count Isochron Diagram………………………………………. 33 9. Geologic Map of Ladon Valles and Vicinity………………………………….. 36 10. Geologic Map of Northern Ladon Valles…………. ………………………….. 37 11. Geologic Map of Southern Ladon Valles…….………………………………... 37 12. Stratigraphic Column of Ladon Valles and Vicinity……………………….….. 38 13. Cross-sectional Profiles of Various Martian Valleys………………………..…. 48 14. Profiles of the Channels of Ladon Valles……………………………………… 49 15. Cross-sectional Profile Showing V-shape of Main Channel Floor……………. 50 16. Aerial Views of Channels Analyzed for their Sinuosity……………………..... 51 17. Landforms of Ladon Valles………………………………………………...…. 53 18. Profiles Used to Produce Discharge Estimates in Ladon Valles……………… 54 19. Crater-counting curves for Units Outside the Main Channel…………………. 63 20. Ladon Valles Main Channel Crater Retention Data…………………………... 65 9 21. Comparison of Discharge Estimates Including My Results…………………... 68 22. Flow Velocity as a Function of Channel Floor Slope………………………......73 23. Crater-retention Data for All Four Anastomosing Channels……………….…. 79 24. Cross-section of Profile C2......………………………………………………... 85 25. Possible Evidence of the Extent of Ladon Valles…………………………….. 89 10 1. Introduction 1.1 Geologic Setting Present-day Mars is a dry and dusty world where water is presently unstable on the surface (Carr, 2006; Carr and Head, 2010). Yet the planet features ancient landforms where water erosion or deposition is evident. Many were likely developed on early Mars when its atmosphere generally may have been denser and the surface was warmer (Carr and Head, 2010; Milliken and Bish, 2010; Grant et al, 2009a). Margaritifer Terra (Fig. 1) is home to many such landforms: valley networks, outflow channels, and depositional basins are dispersed throughout. Loire, Samara, and Panará Valles are its major valley networks. Uzboi, Ladon and Morava Valles comprised what Grant and Parker (2002) refer to as a “mesoscale outflow system”, while Ladon Basin, and Holden and Eberswalde craters are Margaritifer Terra’s most notable depositional basins (Fig. 1). As part of the Uzboi- Ladon-Morava drainage system (Mangold et al., 2012 and