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- Calcareous clay or intimate mixture
of clay and particles of calcite or
dolomite, usually shell fragments.
Source: Leet, L. Don. 1982.
Physical Geology, 6th Edition. Englewood Cliffs, NJ: Prentice-Hall
- a. An old term loosely applied to a variety of materials, most of which
occur as loose, earthy deposits consisting chiefly of an intimate mixture
of clay and calcium carbonate, formed under marine or esp. freshwater
conditions; specif. an earthy substance containing 35% to 65% clay and 65%
to 35% carbonate. Marl is usually gray; it is used esp. as a fertilizer
for acid soils deficient in lime. In the Coastal Plain area of
Southeastern United States, the term has been used for calcareous clays,
silts, and sands, esp. those containing glauconite (greensand marls); and
for newly formed deposits of shells mixed with clay. AGI
b. A soft, grayish to white, earthy or powdery, usually impure, calcium
carbonate precipitated on the bottoms of present-day freshwater lakes and
ponds, largely through the chemical action of aquatic plants, or forming
deposits that underlie marshes, swamps, and bogs that occupy the sites of
former (glacial) lakes. The calcium carbonate may range from 90% to less
than 30% . Syn: bog lime
c. A term occasionally used (as in Scotland) for a compact, impure,
argillaceous limestone. Etymol: French marle. AGI
Source:
Dictionary of Mining, Mineral, and Related Terms
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