and is mostly orthoclase
and microcline. Mica is common, ranging from 3.7% to 13.7% (av. 7.8%)
and is most abundant infine-grained sandstones. Biotite is extensively altered to chlorite, and is dominant over muscovite. Authigenic
minerals are mainly carbonate, with subordinate chlorite and
kaolinite. Matrix contents are usually low (b5%).