Those higher in the group include up to 10% of quartzite from the Midlands, igneous rocks from Wales, and chert from the Upper Greensand of southeastern England The BGS Lexicon of Named Rock Units.
Those higher in the group include over 10% of quartzite from the Midlands, igneous rocks from Wales, and chert from the Upper Greensand of southeastern England. This exotic rock component was introduced by rivers draining central and eastern England The BGS Lexicon of Named Rock Units.