Table 1.

Expected Characteristics of Megabreccia Deposits From Four Known Megabreccia Formation Mechanisms

Formation mechanism	Distribution	Texture/lithology	Block sizes	References
Ballistic ejecta	Circumferential to outer and inner crater ring Extend >2 crater radii	Multitude of textures/lithologies Potential sorting of textures/lithologies with distance	Potential dependency on distance from crater center	Hörz (1982)
Ground-hugging, ejecta-related melt flows	Not necessarily circumferential Should extend beyond the outer ring Occurs locally	Significant melt component Flow/dike/pseudotachylite structures	No particular expectations	Komatsu et al. (2007) and Osinski et al. (2011)
Crater floor/central peak fracturing and/or melt sheet formation	Occurs within inner ring or central peak	Uplifted/faulted blocks Preimpact lithologies Should be in matrix of melt	Primarily large blocks (100s of meters)	Caudill et al. (2012), Schultz (1976), Quantin et al. (2012), and Krüger et al. (2016)
Gravitational flow during crater collapse	Circumferential to inner crater rim Occurs primarily within transient crater and faulted region (likely between outer and inner ring)	Multitude of textures/lithologies Evidence for ground transport No spatial sorting, complete heterogeneity	Potential dependency on elevation but not distance	Belza et al. (2012), Stöffler et al. (2004), and Trowbridge et al. (2019)