marl
- n a loose and crumbling earthy deposit consisting mainly of calcite or dolomite; used as a fertilizer for soils deficient in lime
- In that country of slow streams, red marl and ancient orchards, Frost took his children picnicking, spent days tramping the country looking for flowers.
- Though research on extracting kerogen from marl began in the 1920s, shale oil went undeveloped because its production cost always exceeded the market price of crude.
- The slopes of northwestern Colorado, southwestern Wyoming and northeastern Utah are layered with marl, a limestone in which a fossil fuel called kerogen is embedded.