중생대 백악기의 녹사층 사이에 형성된 점토질 지층인 골트계.
A formation of stiff blue clay or marl from the Cretaceous period, situated between the Upper and Lower Greensand.
예문:
"The galt formation is particularly prominent in the cliffs of Folkestone."
"Geologists analyzed the mineral composition of the galt to date the surrounding strata."