The "Shammar group" is a silicic and volcaniclastic sequence in northwestern Saudi Arabia.2
"USGS Volcano Hazards Program Glossary - Silicic". USGS. 2013-09-19. Retrieved 2016-01-02. https://volcanoes.usgs.gov/vsc/glossary/silicic.html ↩
Kellogg, Karl S. (1984), Reconnaissance geology of the Qufar Quadrangle, sheet 27/41 D, Kingdom of Saudi Arabia (PDF), Denver: United States Geological Survey, pp. 1–33, retrieved 2019-01-06 https://pubs.usgs.gov/of/1984/0159/report.pdf ↩