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→Carbonate sediments and environments
[[file:carbonate-reservoir-models-facies-diagenesis-and-flow-characterization_fig1.png|thumb|left|{{figure number|1}}Dunham's<ref name=pt06r29>Dunham, R. J., 1962, [http://archives.datapages.com/data/specpubs/carbona2/data/a038/a038/0001/0100/0108.htm Classification of carbonate rocks according to depositional texture], in, Classifications of Carbonate Rocks—A Symposium: AAPG Memoir 1, p. 108–121.</ref> classification of carbonate rocks according to depositional texture.<ref name=pt06r138>Swanson, R. G., 1981, Sample examination manual: [http://store.aapg.org/detail.aspx?id=603 AAPG Methods in Exploration 1], 65 p.</ref>]]
[[file:carbonate-reservoir-models-facies-diagenesis-and-flow-characterization_fig1.png|thumb|left|{{figure number|1}}Dunham's<ref name=pt06r29>Dunham, R. J., 1962, [http://archives.datapages.com/data/specpubs/carbona2/data/a038/a038/0001/0100/0108.htm Classification of carbonate rocks according to depositional texture], in, Classifications of Carbonate Rocks—A Symposium: AAPG Memoir 1, p. 108–121.</ref> classification of carbonate rocks according to depositional texture.<ref name=pt06r138>Swanson, R. G., 1981, Sample examination manual: [http://store.aapg.org/detail.aspx?id=603 AAPG Methods in Exploration 1], 65 p.</ref>]]
The majority of carbonate sediments are produced in shallow, warm ocean waters by extraction of [[Carbonate|calcium carbonate]] from seawater by organisms to form their shells or skeletal material. The sediments are composed of a spectrum of sizes and [[pore geometries]]. The [[Carbonate classifications|Dunham classification]] ([[:file:carbonate-reservoir-models-facies-diagenesis-and-flow-characterization_fig1.png|Figure 1]]) describes depositional textures in a manner that can be related to [[Pore system shapes|pore geometries]]. The [[Grain-supported carbonates|grain-supported]] textures tend to have larger pore sizes than do [[Mud-supported carbonates|mud-supported]] textures. The textures have different geometries in different [[depositional environments]].
The majority of carbonate sediments are produced in shallow, warm ocean waters by extraction of [[Carbonate|calcium carbonate]] from seawater by organisms to form their shells or skeletal material. The sediments are composed of a spectrum of [[Grain sizes|sizes]] and [[Pore system shapes|pore geometries]]. The [[Carbonate classifications|Dunham classification]] ([[:file:carbonate-reservoir-models-facies-diagenesis-and-flow-characterization_fig1.png|Figure 1]]) describes depositional textures in a manner that can be related to |pore geometries. The [[Grain-supported carbonates|grain-supported]] textures tend to have larger pore sizes than do [[Mud-supported carbonates|mud-supported]] textures. The textures have different geometries in different [[depositional environments]].
[[file:carbonate-reservoir-models-facies-diagenesis-and-flow-characterization_fig2.png|thumb|{{figure number|2}}Carbonate depositional environments. (Diagram by R. G. Loucks and C. R. Handford, unpublished.)]]
[[file:carbonate-reservoir-models-facies-diagenesis-and-flow-characterization_fig2.png|thumb|{{figure number|2}}Carbonate depositional environments. (Diagram by R. G. Loucks and C. R. Handford, unpublished.)]]
The peritidal depositional environment is complex ([[:file:carbonate-reservoir-models-facies-diagenesis-and-flow-characterization_fig2.png|Figure 2]]). Sediments deposited between mean high and mean low tide are called ''[[intertidal sediments]]'', sediments deposited above mean high tide are called ''[[supratidal sediments]]'', and sediments deposited below mean low tide are called ''[[subtidal sediments]]''. In arid and semi-arid climates, evaporite flats ([[sabkhas]]) are present from which [[gypsum]] and [[halite]] are deposited. [[Sand dunes|Eolian sand dunes]] composed of siliciclastic or carbonate grains may form on the supratidal surface.
The peritidal depositional environment is complex ([[:file:carbonate-reservoir-models-facies-diagenesis-and-flow-characterization_fig2.png|Figure 2]]). Sediments deposited between mean high and mean low tide are called ''[[intertidal sediments]]'', sediments deposited above mean high tide are called ''[[supratidal sediments]]'', and sediments deposited below mean low tide are called ''[[subtidal sediments]]''. In arid and semi-arid climates, evaporite flats ([[sabkhas]]) are present from which [[gypsum]] and [[halite]] are deposited. [[Sand dunes|Eolian sand dunes]] composed of siliciclastic or carbonate grains may form on the supratidal surface.
The shallow shelf interior environment ([[:file:carbonate-reservoir-models-facies-diagenesis-and-flow-characterization_fig2.png|Figure 2]]) is dominated by low-energy waters that allow lime mud to accumulate. [[Storm deposits and currents|Storms]], however, churn the sediment into [[suspension]], winnowing out the fine-sized material and concentrating the coarse material. Near shorelines, the shelf environment may be composed of offshore [[bars]] and [[spits]] oriented parallel to shoreline. Shorelines that face heavy wave action accumulate [[carbonate sand]] or gravel. Tidal currents are concentrated in channels between islands and produce [[tidal deltas]] on the lee side of the island.
The shallow shelf interior environment ([[:file:carbonate-reservoir-models-facies-diagenesis-and-flow-characterization_fig2.png|Figure 2]]) is dominated by low-energy waters that allow lime mud to accumulate. [[Storm deposits and currents|Storms]], however, churn the sediment into [[suspension]], winnowing out the fine-sized material and concentrating the coarse material. Near shorelines, the shelf environment may be composed of offshore [[bars]] and [[spits]] oriented parallel to shoreline. Shorelines that face heavy wave action accumulate [[carbonate sand]] or gravel. [[Tidal currents]] are concentrated in channels between islands and produce [[tidal deltas]] on the lee side of the island.
The shelf margin complex ([[:file:carbonate-reservoir-models-facies-diagenesis-and-flow-characterization_fig2.png|Figure 2]]) is characterized by the presence of [[carbonate sands]] and [[reefs]]. Reefs are commonly found at the shelf edge where their rigid framework can withstand strong wave action and they can take advantage of the nutrients upwelling from the deeper waters. [[Carbonate sands]] derived from a reef or from plants and animals inhabiting the shelf edge accumulate along a wide belt that follows the break between the shelf edge and the slope. Tidal and storm currents mold the sand belt into tidal channels and bars.
The shelf margin complex ([[:file:carbonate-reservoir-models-facies-diagenesis-and-flow-characterization_fig2.png|Figure 2]]) is characterized by the presence of [[carbonate sands]] and [[reefs]]. [[Reefs]] are commonly found at the shelf edge where their rigid framework can withstand strong wave action and they can take advantage of the nutrients upwelling from the deeper waters. [[Carbonate sands]] derived from a reef or from plants and animals inhabiting the shelf edge accumulate along a wide belt that follows the break between the shelf edge and the slope. [[Tidal currents|Tidal]] and [[Storm deposits and currents|storm currents]] mold the sand belt into tidal channels and bars.
The slope ([[:file:carbonate-reservoir-models-facies-diagenesis-and-flow-characterization_fig2.png|Figure 2]]) is dominated by sediment transport seaward from the shelf margin. Fine-grained sediment settles to the bottom forming thin-bedded [[mudstones]], while slumps, [[debris flows]], and [[turbidity currents]] form coarse-grained bodies of [[breccia]], [[conglomerate]], and [[carbonate sand]]. The resulting [[facies patterns]] depend upon the relief of the shelf margin and the nature of the shallow water portion of the margin.<ref name=pt06r87>Mcllreath, I. A., James, N. P., 1984, Carbonate slopes, in Walker, R. G., ed., Facies Models: Geoscience Canada Reprint Series 1, p. 245–258.</ref>
The slope ([[:file:carbonate-reservoir-models-facies-diagenesis-and-flow-characterization_fig2.png|Figure 2]]) is dominated by sediment transport seaward from the shelf margin. Fine-grained sediment settles to the bottom forming thin-bedded [[mudstones]], while slumps, [[debris flows]], and [[turbidity currents]] form coarse-grained bodies of [[breccia]], [[conglomerate]], and [[carbonate sand]]. The resulting [[facies patterns]] depend upon the relief of the shelf margin and the nature of the shallow water portion of the margin.<ref name=pt06r87>Mcllreath, I. A., James, N. P., 1984, Carbonate slopes, in Walker, R. G., ed., Facies Models: Geoscience Canada Reprint Series 1, p. 245–258.</ref>