Gault clay
Concise Oxford English Dictionary © 2008 Oxford University Press:
Gault clay /gɔːlt/
▶noun Geology a series of Cretaceous clays and marls forming strata in southern England.
– origin C16: possibly rel. to Old Swed. galt, neut. of galder ‘barren’.
'Gault clay' also found in these Oxford entries:

