Lahar Transport
Because lahars move as a viscous flow, they do not have the degree of internal turbulence of a stream. In fact flow more closely resembles a lava flow or glacier. One consequence is that lahars, like glaciers, can carry very large objects. Another is that they can carry quite delicate objects, items that would be quickly broken up in stream transport. An-easily recognized example is "Jig-saw puzzle" rocks, clasts with internal fractures that have fallen apart after transport, but remain with the pieces in the same relative position.
Photo by James Maynard © 2009 - free use with attribution
A second type is very soft clasts, for example those with extensive hydrothermal alteration.
Photo by James Maynard © 2009 - free use with attribution