Here Dott opines on wacke, and on graywack. And that’s not all:
“Wacke, graywacke and matrix; what approach to immature sandstone classification?” Robert H. Dott [pictured here], Journal of Sedimentary Research 34, no. 3 (1964): 625-632.
“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.”