A sedimentary clay and lime rock or soil which used to be used as a fertilizer: clearly it is this meaning in the Woolf quotation below.  It also refers to a mottled yarn of different colours, or cloth made of this. ‘Marly’ is the adjective.
And enjoy Orlando’s getting carried away on a flight of eloquence until his author reins him in.
‘It is marl we tread and fiery cobbles scorch our feet. By the truth we are undone. Life is a dream. ‘Tis waking that kills us. He who robs us of our dreams robs us of our life – (and so on for six pages, but the style is tedious and may well be dropped).’
Source: Virginia Woolf, Orlando, ed. Rachel Bowlby, Oxford: World’s Classics, 1992, p. 195
