'Marlstone' definitions:

Definition of 'marlstone'

noun

Metamorphic rock with approximately the same composition as marl [syn: marlite, marlstone]

From: GCIDE

Marlstone \Marl"stone`\, n. (Geol.) A sandy calcareous straum, containing, or impregnated with, iron, and lying between the upper and lower Lias of England. [1913 Webster]