Washington University in St. Louis Washington University Open Scholarship Arts & Sciences Electronic Theses and Dissertations Arts & Sciences Winter 12-15-2015 Investigating the Complexity of Impact Crater Ejecta Michael Raymond Zanetti Washington University in St. Louis Follow this and additional works at: https://openscholarship.wustl.edu/art_sci_etds Part of the Earth Sciences Commons Recommended Citation Zanetti, Michael Raymond, "Investigating the Complexity of Impact Crater Ejecta" (2015). Arts & Sciences Electronic Theses and Dissertations. 694. https://openscholarship.wustl.edu/art_sci_etds/694 This Dissertation is brought to you for free and open access by the Arts & Sciences at Washington University Open Scholarship. It has been accepted for inclusion in Arts & Sciences Electronic Theses and Dissertations by an authorized administrator of Washington University Open Scholarship. For more information, please contact [email protected]. WASHINGTON UNIVERSITY IN ST. LOUIS Department of Earth and Planetary Sciences Dissertation Examination Committee: Bradley L. Jolliff, Chair Ramesh K. Agarwal Robert F. Dymek Harald Hiesinger Randy L. Korotev William B. McKinnon Investigating the Complexity of Impact Crater Ejecta by Michael Raymond Zanetti A dissertation presented to the Graduate School of Arts & Sciences of Washington University in partial fulfillment of the requirements for the degree of Doctor of Philosophy December 2015 St. Louis, Missouri 1 © 2015, Michael Raymond Zanetti 2 Table of Contents List of Figures ................................................................................................................................ vi List of Tables ................................................................................................................................. ix Acknowledgements ..........................................................................................................................x Abstract of the Dissertation ......................................................................................................... xiv Chapter 1: Introduction to the Dissertation ................................................................................1 1.1 Impact Crater Ejecta Emplacement ...................................................................................... 3 1.2 Goals and Objectives ............................................................................................................ 7 1.3 Major Results ....................................................................................................................... 8 1.3.1 Chapter 2 ....................................................................................................................... 8 1.3.2 Chapter 3 ..................................................................................................................... 10 1.3.3 Chapter 4 ..................................................................................................................... 12 1.4 Statement of Labor ............................................................................................................. 15 1.5 Copyright and Permissions ................................................................................................. 16 Chapter 1 References ................................................................................................................ 17 Chapter 1 Figures ...................................................................................................................... 18 Chapter 2: The Geology and Geomorphology of Aristarchus Crater ....................................21 Abstract ..................................................................................................................................... 21 2.1 Introduction ........................................................................................................................ 22 2.1.1 Geologic Background of the Aristarchus Region ....................................................... 22 2.1.2 General Geology of the Crater ejecta .......................................................................... 27 2.1.3 Age Estimates ............................................................................................................. 30 2.1.4 Objectives ................................................................................................................... 31 2.2 Data and Methods ............................................................................................................... 31 2.2.1 Datasets ....................................................................................................................... 31 2.2.2 Methods....................................................................................................................... 35 2.3 Results: ............................................................................................................................... 37 2.3.1 Morphometry .............................................................................................................. 38 2.3.2 Geomorphologic Map ................................................................................................. 40 2.3.3 Geologic Map from Image Classification ................................................................... 57 2.4 Discussion .......................................................................................................................... 59 ii 2.4.1 Influence of pre-existing topography .......................................................................... 59 2.4.2 Impactite distribution .................................................................................................. 61 2.4.3 Central peak Characteristics ....................................................................................... 63 2.4.4 Stratified Boulder Observations and Formation ......................................................... 63 2.4.5 Morphology vs. Composition ..................................................................................... 67 2.5 Geologic Map Discussion: ................................................................................................. 68 2.5.1 Central Peak, Crater Floor, and SW Ejecta (Units CP, CF, SWE) ............................. 69 2.5.2 Crater Wall Units (WW and NW) .............................................................................. 75 2.5.3 Ejecta Units (WE, SE, NE) ......................................................................................... 77 2.5.4 Pre-impact Surface (WP, SM) .................................................................................... 82 2.5.5 Anomalous Plateau Units Correlated with Aristarchus Ejecta ................................... 83 2.5.6 Regional Emplacement of Evolved-Lithologies ......................................................... 85 2.5.7 On the possibility of a South AP Crater ..................................................................... 88 2.6 Geologic History of the Southern Aristarchus Plateau ...................................................... 90 2.7 Conclusions ........................................................................................................................ 91 2.8 Acknowledgements: ........................................................................................................... 93 Chapter 2 References: ............................................................................................................... 94 Chapter 2 Figures: ..................................................................................................................... 97 Chapter 2 Tables: .................................................................................................................... 135 Chapter 3: Evidence for Auto-Secondary Cratering of Copernican-Age Continuous Ejecta Deposits on the Moon.................................................................................................................138 Abstract ................................................................................................................................... 138 3.1 Introduction ...................................................................................................................... 139 3.2 Methods ............................................................................................................................ 142 3.3 Results .............................................................................................................................. 145 3.3.1 Crater Density Mapping At Tycho ........................................................................... 145 3.3.2 Crater Density Variation at Aristarchus Crater:........................................................ 146 3.3.3 Ejecta Blanket CSFDs............................................................................................... 146 3.3.4 CSFD Based on Density ........................................................................................... 147 3.3.5 High-resolution Melt-Ejecta CSFD comparison:...................................................... 148 3.4 Discussion ........................................................................................................................ 148 iii 3.4.1 Crater Density Variation on Copernican Ejecta Blankets: ....................................... 148 3.4.2 Crater Density and Apparent Age ............................................................................