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Composition
Description
Dense, uniform, fine grained rock with conchoidal fracture. Faint, weak laminations running parallel to top of picture (see next to penny). The laminations are probably algal laminates, produced on tidal flats by colonies of blue-green algae.
Tectonic Association
carbonates of all types are commonly associated with regions of tectonic stability and tropical climates, that is no mountain building, and stable, shallow water environments associated with continental shelves or epeiric (epicontinental) seas.
Go to Carbonate Tectonics for more explanation.
micrite is one of the most common carbonate rocks. Most of what people call " limestone" is largely or exclusively micrite. As with clay (shale) it is deposited in generally quiet water, and appears in any environment where those conditions exist.
Often we associate quiet water with deep water, where waves and currents do not touch bottom. But with carbonates that may not always be a good rule. micrites (especially algal laminated micrites, as is this specimen) form readily in the upper regions of tidal flats (Upper Intertidal And Supertidal), where periodic exposure to air is common.
Description
Dense, uniform, fine grained rock with conchoidal fracture. This
micrite has no discernable structure to it at all, and thus shows the nature of the pure rock. One note, relatively pure
micrites are light gray or tan (as this specimen), but it is not uncommon for
micrites to be contaminated. Which leads to the cardinal rule about sedimentary rocks - "
Never Trust Color" when it comes to identifying sedimentary rocks. It will get you into trouble more times than not.
Tectonic Association
carbonates of all types are commonly associated with regions of tectonic stability and tropical climates, that is no mountain building, and stable, shallow water environments associated with continental shelves or epeiric (epicontinental) seas.
micrite is one of the most common carbonate rocks. Most of what people call " limestone" is largely or exclusively micrite. As with clay (shale) it is deposited in generally quiet water, and appears in any environment where those conditions exist. This specimen could have come from a tidal lake, or a subtidal lagoon, or some similar environment.