E. Petrology and Distribution of Returned

CONTENTS Page Introduction .................................................................................................................. 127 Megascopic structures ...................................................................................................... 128 Hand-specimen petrology .................................................................................................. 128 Megascopic rock types ..................................................................................................... 130 Crystalline rocks ........................................................................................................ 130 Glass ..................................................................................................................... 130 Breccias .................................................................................................................. 130 Thin-section petrology ...................................................................................................... 131 Crystalline rocks ....................................................................................................... 131 Igneous groups (C1) ............................................................................................... 131 Metaclastic groups (C2) ......................................................................................... 131 Breccias .................................................................................................................. 133 Group B, (light matrix, light clasts) ............................................................................ 133 Group B2 (light matrix, dark clasts) ........................................................................... 134 Group B3 (intermediate matrix color, light and dark clasts) ................................................ 134 Group B4 (dark matrix, light clasts) ........................................................................... 134 Group Bs (dark matrix, dark clasts) ............................................................................ 134 Interpretation of the breccias .................................................................................... 134 Chronology of Apollo 16 rocks ........................................................................................... 140 Areal distribution of classified samples .................................................................................. 143 Summary and conclusions ................................................................................................. 146 Acknowledgments ........................................................................................................... 146