allochem


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allochem

[′a·lō‚kem]
(geology)
Sediment formed by chemical or biochemical precipitation within a depositional basin; includes intraclasts, oolites, fossils, and pellets.
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In some cases, stylolites are generated in the middle of the allochem while in some cases they are present as small discontinuous lines reflecting chemical compaction on a very local scale.
Clast type 2 has an allochem suite that is almost completely dominated by strongly aligned disarticulated and abraded thin shelled bivalves (IPosidonia) and small quantities of fine micropeloids that appear light grey in PPL.
These microfacies have been studied on the basis of orthochem and allochem elements, their percentages, and their texture in the stratigraphy section [19].
The term "allochem" is applied to carbonate grains greater than 0.062mm Rich, 1964.
Allochem. A particle in a carbonate rock; i.e., not mud or cement.
The two (2) microfacies and four (4) sub-microfacies with discrete texture, fossils content and allochem types are mudstone to wackestone microfacies and wackestone microfacies, sub microfacies are Larger foraminiferal mudstone to wackestone sub-microfacies, larger benthic wackestone sub-microfacies, bioclastic wackestone sub-microfacies and Nummulitic wackestone sub-microfacies.
Additional allochem particles include pelloids, some spherical single-walled calcispheres, and rare microcrinoid ossicles.
The microfacies is characterized by skeletal allochems which are the only allochemical constituents marked by moderate diversity of organisms with allochem to micrite ratio of 7:3.
The microfacies analysis details the allochem matrix textural features and fossils content of the lithofacies (WF1-WF9).
The allochem and matrix ratio is3:7, according to visual estimation, the average relative abundance of various faunal and floralconstituents is Lockhartia (15%), Operculina(1%) and Milliolid up to (7%).
On the basis of detailed petrographic analysis (i.e., allochem type, composition, texture, sedimentary structures and rock types), three microfacies and five sub microfacies are recognized (Fig.