Some Evidence Regarding the Kind and Quantity of Sediment Transported by Density Currents

Density-currents are of major importance as transporting and sorting agents for fine sediment. Under unusual or extreme conditions they have a part in the distribution of surprisingly coarse material. The magnitude of the work they perform in sedimentation may have been obscured somewhat in recent years because there has been a tendency to think of density-currents almost solely as turbid underflows in bodies of still water, especially in reservoirs that are fed by muddy rivers. Density-currents are not limited to underflows, be they turbid or otherwise. Their occurrence is confined neither to reservoirs in particular nor to bodies of water in general. For example, dust storms usually are true density-currents [see 1 of "References" at end of paper]. The importance of the atmosphere as a transporting and sorting agent is well known, and has been demonstrated clearly by evidence gathered by JOHAN AUGUST UDDEN[2], EDWARD ELWAY FREE[3], and many others. The fact that needs wider recognition is that the atmospheric transportation of sediment is accomplished very largely by density-currents