Cap carbonate See also References Navigation menu"Are Proterozoic cap carbonates and isotopic excursions a record of gas hydrate destabilization following Earth's coldest intervals?"10.1130/0091-7613(2001)0292.0.CO;20091-7613"Neoproterozoic cap carbonates: a critical appraisal of existing models and the plumeworld hypothesis"10.1111/j.1365-3121.2005.00638.x0954-4879"On Neoproterozoic Cap Carbonates as Chronostratigraphic Markers"10.1007/1-4020-5202-2_9.pdfWhat are Cap Carbonates?expanding ite
Sedimentary rocksGlaciologyGeology stubs
carbonate rockssedimentaryglaciationsgeological recordprecipitationgreenhouse gasescarbon dioxideatmospherealbedocarbonic acidacid rainsilicateprecipitatesedimentary rockGaskiers glaciationglobal in extent
Cap carbonates are layers of distinctively textured carbonate rocks which typically form the uppermost layer of sedimentary sequences reflecting major glaciations in the geological record.[1][2]
The rising temperatures, and increased oceanic surface area - due to reduced ice cover and rising sea levels - at the end of a glaciation increase the rate of precipitation.
High concentrations of greenhouse gases such as carbon dioxide (CO2) must build up in the atmosphere to overcome the effect of the high reflectivity (albedo) of ice and allow temperatures to rise sufficiently to begin melting.
Increased precipitation dissolves carbon dioxide from the atmosphere, falling as a weak carbonic acid - acid rain.
This would weather exposed silicate and carbonate rock, including readily-attacked glacial debris, which would release large amounts of calcium. When washed into the ocean, these precipitate to form distinctively textured layers of carbonate sedimentary rock.
A heavily debated cap carbonate appears at the top of the Gaskiers glaciation, believed by many to be global in extent.[3]
See also
- Marinoan glaciation
- Sturtian glaciation
- Boundaries of the Ediacaran Period
- Snowball Earth
- Katanga Supergroup
References
^ Sohl, Linda E.; Christie-Blick, Nicholas; Kennedy, Martin J. (2001-05-01). "Are Proterozoic cap carbonates and isotopic excursions a record of gas hydrate destabilization following Earth's coldest intervals?". Geology. 29 (5): 443–446. doi:10.1130/0091-7613(2001)0292.0.CO;2. ISSN 0091-7613..mw-parser-output cite.citationfont-style:inherit.mw-parser-output .citation qquotes:"""""""'""'".mw-parser-output .citation .cs1-lock-free abackground:url("//upload.wikimedia.org/wikipedia/commons/thumb/6/65/Lock-green.svg/9px-Lock-green.svg.png")no-repeat;background-position:right .1em center.mw-parser-output .citation .cs1-lock-limited a,.mw-parser-output .citation .cs1-lock-registration abackground:url("//upload.wikimedia.org/wikipedia/commons/thumb/d/d6/Lock-gray-alt-2.svg/9px-Lock-gray-alt-2.svg.png")no-repeat;background-position:right .1em center.mw-parser-output .citation .cs1-lock-subscription abackground:url("//upload.wikimedia.org/wikipedia/commons/thumb/a/aa/Lock-red-alt-2.svg/9px-Lock-red-alt-2.svg.png")no-repeat;background-position:right .1em center.mw-parser-output .cs1-subscription,.mw-parser-output .cs1-registrationcolor:#555.mw-parser-output .cs1-subscription span,.mw-parser-output .cs1-registration spanborder-bottom:1px dotted;cursor:help.mw-parser-output .cs1-ws-icon abackground:url("//upload.wikimedia.org/wikipedia/commons/thumb/4/4c/Wikisource-logo.svg/12px-Wikisource-logo.svg.png")no-repeat;background-position:right .1em center.mw-parser-output code.cs1-codecolor:inherit;background:inherit;border:inherit;padding:inherit.mw-parser-output .cs1-hidden-errordisplay:none;font-size:100%.mw-parser-output .cs1-visible-errorfont-size:100%.mw-parser-output .cs1-maintdisplay:none;color:#33aa33;margin-left:0.3em.mw-parser-output .cs1-subscription,.mw-parser-output .cs1-registration,.mw-parser-output .cs1-formatfont-size:95%.mw-parser-output .cs1-kern-left,.mw-parser-output .cs1-kern-wl-leftpadding-left:0.2em.mw-parser-output .cs1-kern-right,.mw-parser-output .cs1-kern-wl-rightpadding-right:0.2em
^ Shields, Graham A. (August 2005). "Neoproterozoic cap carbonates: a critical appraisal of existing models and the plumeworld hypothesis". Terra Nova. 17 (4): 299–310. doi:10.1111/j.1365-3121.2005.00638.x. ISSN 0954-4879.
^ Corsetti, Frank A.; Lorentz, Nathaniel J. (2006), Xiao, Shuhai; Kaufman, Alan J., eds., "On Neoproterozoic Cap Carbonates as Chronostratigraphic Markers", Neoproterozoic Geobiology and Paleobiology, Topics in Geobiology, Springer Netherlands, pp. 273–294, doi:10.1007/1-4020-5202-2_9.pdf, ISBN 9781402052026, retrieved 2019-03-02
What are Cap Carbonates? at www.snowballearth.org
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