Angles of repose for naturally occurring materials are known to be a function of, among other geologic parameters, the acceleration of gravity and cohesion between particles. Thus, steeper angles may have been recorded in ancient sediments because Earth's acceleration of gravity was less than now. Published data suggest that eolian and aqueous sediments have documented these changes. Previously, angles of repose steeper than modern angles were attributed to structural steepening and soft-sediment deformation. More detailed study is required to separate the contribution that each of many factors may have had in specific cases of ancient angles of deposition.