Sediments of arenaceous or sandy texture are characterized by grain sizes which fall between 1/16 and 2 mm.
The arenaceous rocks (arenites) include all those clastic sedimentary rocks whose particle sizes range from 2 to 0.06 mm.
The formation has pebbly sandstones, arkosic sandstones and siltstones, and intercalated thin arenaceous shales.
The coal-rich and largely argillaceous mid-A to mid-C Westphalian succession, and the coal-poor and largely arenaceous later C/early D Westphalian succession are very different.
