300px, thumbnail, Shale rip-up clasts in a nearshore marine sandstone, Matilija Fm. Topatopa Mountains, California. 300px, thumbnail, A giant shale rip-up clast at the base of a high-density turbidite, Cozy Dell Fm. Topatopa Mountains, California. Rip-up clasts are

gravel Gravel is a loose aggregation of rock fragments. Gravel occurs naturally throughout the world as a result of sedimentary and erosive geologic processes; it is also produced in large quantities commercially as crushed stone. Gravel is classifi ...

-size pieces of

clay Clay is a type of fine-grained natural soil material containing clay minerals (hydrous aluminium phyllosilicates, e.g. kaolin, Al2 Si2 O5( OH)4). Clays develop plasticity when wet, due to a molecular film of water surrounding the clay par ...

mud A MUD (; originally multi-user dungeon, with later variants multi-user dimension and multi-user domain) is a Multiplayer video game, multiplayer Time-keeping systems in games#Real-time, real-time virtual world, usually Text-based game, text-bas ...

created when an erosive current flows over a bed of clay or mud and removes pieces of clayey

sediment Sediment is a naturally occurring material that is broken down by processes of weathering and erosion, and is subsequently transported by the action of wind, water, or ice or by the force of gravity acting on the particles. For example, sand an ...

, and transports them some distance. Because clayey sediments can be quite cohesive, even when freshly deposited, large clasts of clayey sediment can be ripped up, transported and subsequently preserved when the eroding current finally deposits its sediment. After deposition and deep burial by the accumulation of additional sediments, diagenesis transforms the

-size pieces of clayey sediment into

shale Shale is a fine-grained, clastic sedimentary rock formed from mud that is a mix of flakes of clay minerals (hydrous aluminium phyllosilicates, e.g. kaolin, Al2 Si2 O5( OH)4) and tiny fragments (silt-sized particles) of other minerals, especial ...

mudstone Mudstone, a type of mudrock, is a fine-grained sedimentary rock whose original constituents were clays or muds. Mudstone is distinguished from '' shale'' by its lack of fissility (parallel layering).Blatt, H., and R.J. Tracy, 1996, ''Petrology. ...

rip-up clasts. Shale rip-up clasts are often found at the base of sandy turbidites, in

lag deposit A lag deposit is the deposition of material winnowed by physical action. Aeolian processes, fluvial processes, and tidal processes can remove the finer portion of a sedimentary deposit leaving the coarser material behind. Lag deposits are found i ...

s at the base of channelized

sandstones Sandstone is a clastic sedimentary rock composed mainly of sand-sized (0.0625 to 2 mm) silicate grains. Sandstones comprise about 20–25% of all sedimentary rocks. Most sandstone is composed of quartz or feldspar (both silicates) b ...

, and associated with subaqueous dunes and bars.Jackson, J.A., Mehl, J.P. Klaus and Neuendorf, K.E. (2005), ''Glossary of Geology.'' Springer-Verlag, p. 557.

Notes and references

Sedimentology {{geology-stub