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Groundwater environments
Published in Ian Acworth, Investigating Groundwater, 2019
Limestone is a sedimentary rock composed largely of the mineral calcite (calcium carbonate: CaCO3). Limestone often contains variable amounts of silica in the form of chert or flint, as well as varying amounts of clay, silt and sand as disseminations, nodules or layers within the rock. Limestone can be recognized in the field by its reaction with hydrochloric acid. A few drops of acid will cause the limestone to fizz with the release of CO2. Micrite or microcrystalline carbonate is by far the most common constituent in carbonate rocks. The individual crystals in ancient rocks are < 5 μm in diameter and are now commonly calcite. In modern carbonates, the mud is composed of individual crystals of aragonite and are needle-like in shape.
Sedimentary rocks
Published in W.S. MacKenzie, A.E. Adams, K.H. Brodie, Rocks and Minerals in Thin Section, 2017
W.S. MacKenzie, A.E. Adams, K.H. Brodie
Micrite This term is short for microcrystalline calcite and refers to carbonate sediment with a crystal size less than 5 μm. It forms in the basin of deposition either as a direct precipitate from seawater or from the disintegration of secretions of calcium carbonate associated with organisms such as algae. Carbonate mud is a term which is often used interchangeably with micrite although strictly mud includes material up to 62 μm in size. The crystal size of micrite is much less than the thickness of normal thin sections and so it is not possible to make out individual crystals under the microscope. Micrite often appears medium to dark grey. The outer parts of ooids, peloids and intraclasts are made of micrite.
Fractures characterization of carbonate reservoir using core analyses and borehole image logs
Published in Petroleum Science and Technology, 2023
The sedimentological evidence contained within the limestone, as well as the relevant literature (Yousef et al. 2021a; Yousef, Morozov, and Sudakov 2021), were used to interpret the depositional settings of the Judea Formation sediments over the studied area. The limestones are thought to have formed in lagoonal to inner shelf depositional settings with low to moderate energy (Figure 7). Bivalves, brachiopod detritus, miliolids, bryozoa, gastropods, and foraminifera are all signs of this (Pomar 2001; Lucia 2004). Additionally, this is indicated by the wackestone and/or the wackestone/packstone texture of the sediment (Pomar 2001). The presence of algal laminae, in particular, attests to the development of the lagoon margin and conditions in the shallow open marine/lower intertidal flat (Pomar and Kendall 2008). Inorganic precipitation, bioerosion, biochemical precipitation, and mechanical disintegration of skeletal debris have all been proposed as sources of micrite (Pomar and Kendall 2008; Lucia 2004).