Micrite

Representative Rock Terms Micrite and Dismicrite Fossili ferous Micrite Sparse Biomicrite Packed Biomicrite... 

Figure 5.4. Classification of mixed siliciclastic-carbonate sediments proposed by Mount (1985). It is an unfolded tetrahedron in which the apices are siliciclastic sand, carbonate allochems, siliciclastic mud, and carbonate micrite. For comparison with Folk s (1962) classification, the classification of pure fossiliferous limestone is also plotted.

Bates N.R. and Brand U. (1990) Secular variation of calcium carbonate mineralogy An evaluation of odid and micrite chemistries. Geologishe Rundschau (in press). 

Calvet, F. (1982). Constructive micrite envelope developed in vadose continental... 

Bathurst, R. G. C. (1966). Boring algae, micrite envelopes and lithification of molluscan biosparites. Geological Journal, 5, 15-32. 

Kobluk, D. Risk, M. (1974). Devonian boring algae or fungi associated with micrite tubules. Canadian Journal of Earth Sciences, 11, 1606-10. 

Not nearly as much attention has been paid to the production of lime mud from calcitic sources, but these muds can be the dominant component in peri-reefal (Debenay, 1985) and lagoonal (Reid et al, 1992) environments where 70-90% of the mud may consist of magnesium calcite. This can form from the micritization and recrystallization of skeletal grains (Reid et al, 1992), and the breakdown of foraminiferal tests (Debenay et al, 1999). 

Reid R. P., Macintyre I. G., and Post J. E. (1992) Micritized skeletal grains in Northern Belize Lagoon a major source of Mg-calcite mud. J. Sediment. Petrol. 62, 145-156. 

Jones, B., 1989, Calcite rafts, peloids, and micrite in cave deposits from Cayman Brae, British West Indies, Can. Jour. Earth Scl, 26 654-664. 

Alexandersson, E.T., 1972. Micritization of carbonate particles Processes of precipitation and dissolution in modern shallow-marine sediments Bull. Geol. Inst. Univ. Uppsala, N.S., 3 201-236. 

Micrite (micritic) the semiopaque, micro-crystalline interstitial component (matrix) of limestones consisting of precipitated carbonate (calcite) mud. 

Chalky or powdery Fine loose powder of calcium carbonate as a continuous body with little or no nodule development, consisting of micrite or microspar, with etched silicate grains, peloids and root and fungal-related microfeatures. Commonly is a transitional zone from calcareous soil to nodular horizons... 

Nodular Term synonymous with glaebular and refers to soft to highly indurated concretions of carbonate, or carbonate cemented host material. The margins may be gradational to sharp, and internally the nodules may be uniform, showing concentric laminae or septarian cracks or veins. The nodules can range in shape from spherical to elongate. The nodules typically consist of micrite or less commonly microsparite. Nodular calcrete develops primarily in siliciclastic host material... 

Pisolitic Millimetre- to centimetre-sized coated grains in layers typically only a few centimetres thick but up to metres thick at the bases of slopes. Can develop in a variety of hosts but are common on coarse-grained hosts. Laminae are generally micritic. Inverse grading is commonly seen. Commonly occur above laminar calcretes... 

Loisy, C., Verrecchia, E.P. Dufour, P. (1999) Microbial origin for pedogenic micrite associated with a carbonate paleosol (Champagne, France). Sedimentary Geology 126, 193-204. 

Figure 5.6 Micritic envelopes developed around a former shell fragment that has undergone dissolution and has been partially replaced by secondary porosity and neomorphic spar, Campo de Tiro, Mallorca (cross-polarised light, x10 magnification).

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