Lutite
Lutite is old terminology, which is not widely used, by Earth scientists in field descriptions for fine-grained, sedimentary rocks, which are composed of silt-size sediment, clay-size sediment, or a mixture of both. When mixed with water lutites often disintegrate into mud. Because this is a field term, there is a lack of any precise definition for it based upon specific grain-size characteristics. Lutites include a variety of fine-grained sedimentary rocks, including calcisiltite, calcilutite, claystone, mudstone, shale, and siltstone. It is equivalent to the term mudstone and the Greek-derived term pelite.[1][2] Lutite was first used in 1904 by Grabau,[3] who derived it from the Latin word for mud. He also proposed a number of prefixes to be used with and attached to "lutite" in order to designated various types of lutites. None of these prefixes are used by Earth scientists.[1]
Pettijohn [4] gives the following descriptive terms based on grain size, avoiding the use of terms such as "clay" or "argillaceous" which carry an implication of chemical composition:
| Texture | Common | Greek | Latin |
|---|---|---|---|
| Coarse | gravel(ly) | psephite (psephitic) | rudite (rudaceous) |
| Medium | sand(y) | psammite (psammitic) | arenite (arenaceous) |
| Fine | clay(ey) | pelite (pelitic) | lutite (lutaceous) |
References
- ^ a b Potter, P.E., J.B. Maynard, and P.J. Depetris (2005) Muds and Mudstones. New York, New York, Springer. 279 pp. ISBN 978-3-540-22157-9
- ^ Neuendorf, K.K.E., J.P. Mehl, Jr., and J.A. Jackson, J.A., eds. (2005) Glossary of Geology (5th ed.). Alexandria, Virginia, American Geological Institute. 779 pp. ISBN 0-922152-76-4
- ^ Grabau, A.W. (1904) On the classification of sedimentary rocks. American Geologist. vol. 33, pp. 228-247.
- ^ Pettijohn F. J. (1975), Sedimentary Rocks, Harper & Row, ISBN 0-06-045191-2