- GeoRef, Copyright 2008, American Geological Institute. Reference includes data from Bibliography and Index of North American Geology, U. S. Geological Survey, Reston, VA, United States
It is suggested that sedimentary rock classification systems have become confused because factors of genesis related to tectonics, provenance, depositional process and environment have been included in them. Classification based on description alone is desirable. It is recommended that the term graywacke reflect texture and maturity rather than specific mineral composition. The term arkose is viewed as nearly useless. A system of rock classification depending on proportion of matrix is highly recommended.