In microcrystalline allochemical limestones and biolithites, sharp fabric discontinuities or boundaries may be anticipated as a result of an aggrading neomorphism. Such discontinuities are commonly caused by structural discontinuities in the initial fabric, that is, boundaries between either skeletal components or terrigenous grains and nonskeletal microcrystalline matrix. This important but much neglected feature deserves more attention because many carbonate petrographers interpret sharp boundaries of areas of sparry calcite as diagnostic of void-filling rather than neomorphic calcite. Physico-chemical conditions in packed microcrystalline limestones appear to favor porphyroid neomorphism.

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