Breccias made up of large clasts of stratigraphic units from target rocks are often associated with impact structures, as for example the Ries crater Bunte Breccia. These breccias exhibit chaotic assemblages of polymict blocks ranging in sizes from a few mm up to several meters. On land these deposits will be rapidly eroded and breccia associated with ancient craters may not be well preserved in the sedimentary record. Large impacts events will also induce tsunami waves. Tsunami deposits and large submarine breccias are more likely to be preserved. Detailed sedimentological characteristics of tsunami wave deposition is not fully understood and rarely described in the literature.
The Manson crater in Iowa provides an interesting case of an impact event linked to tsunami
deposits. The Manson crater, previously considered of KT age, is now precisely dated by
Ar-
Ar at 73.8 
0.3 Ma [ Izett et al., 1993]. Izett and coworkers postulated
that such an impact event in the Western Interior seaway must have been recorded in nearby
Upper Cretaceous sediments at a stratigraphic level commensurate with the time of impact.
Shocked quartz and feldspar grains were effectively found in an unusual sandy unit of the Crow
Creek Member in eight South Dakota sections of the Campanian Pierre Shale. The shocked
minerals increase in size and abundance towards the Manson structure and the Crow Creek sand
is interpreted to represent the reworked deposits of a tsunami wave triggered by the Manson
impact [ Izett et al., 1993]. In this case the impact-induced tsunami origin elegantly
explains the deposition of coarse sand in a shale-dominated deep water settings, a
sedimentological feature that had puzzled regional stratigraphers for many years. Similar impact
and coarse sediment associations must exist elsewhere in the sedimentary record.