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definition A generally soft, white, very fine-grained, extremely pure, porous limestone. It forms under marine conditions from the gradual accumulation of skeletal elements from minute planktonic green algae (cocoliths), associated with varying proportions of larger microscopic fragments of bivalves, foraminifera and ostracods. It is common to find flint and chert nodules embedded in chalk. more like this
source; C.S. Harris, 2009, unpublished web page, more like this
Resource original
Concept original
broader original
narrower chalk original
in scheme simplelithology original
is primary topic of chalk