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Highstand shedding
[edit]![](http://upload.wikimedia.org/wikipedia/commons/thumb/c/c5/SlopeShedding.png/464px-SlopeShedding.png)
Highstand shedding is a process in which a carbonate platform produced and sheds most of the sediments into the adjacent basin during highstands of sea level. This process has been observed on all rimmed carbonate platforms in the Quaternary, such as the Great Bahama Bank. Flat topped, rimmed platforms with steep slopes show more pronounced highstand shedding than platforms with gentle slopes and cool water carbonate systems[1].
Highstand shedding is pronounced on tropical carbonate platforms because of the combined effect of sediment production and diagenesis[2].
Sediment production of a platform increases with its size, during highstand the top of the platform is flooded and the productive area is bigger compared to the lowstand conditions, when only a minimal part of the platform is available for production[2].
The effect of increased highstand production is even enhanced by the rapid lithification of carbonate during lowstands, because the exposed platform top is karstified rather than eroded, and do not export sediment[2].
Slope shedding
[edit]Slope shedding is a process typical of microbial platforms, in which the carbonate production is nearly independent from sea level oscillations.
The carbonate factory, composed of microbial communities precipitating microbialites, is insensitive to light and can extend from the platform break down the slope to hundreds of meters in depth. Sea level drops of any reasonable amplitude would not significantly affect the slope production areas.
Microbial boundstone slope systems are remarkably different from tropical platforms in sediment productions profiles, slope readjustment processes and sediment sourcing. Their progradation is independent from platform sediment shedding and largely driven by slope shedding[3].
Examples of margins that may be affected of slope shedding that are characterized by various contributions of microbial carbonate growth to the upper slope and margin, are:
- the Canning Basin in Australia
- the Guilin platform in the southern China
- the Permian of the US Permian Basin
- the middle Triassic carbonate platforms of the Dolomites[3].
Note
[edit]- ^ Wolfgang Schlager (1), John J. G. R (1994). "Highstand Shedding of Carbonate Platforms". SEPM Journal of Sedimentary Research. Vol. 64B. doi:10.1306/D4267FAA-2B26-11D7-8648000102C1865D.
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has extra text (help)CS1 maint: numeric names: authors list (link) - ^ a b c Schlager, Wolfgang (2005). Carbonate Sedimentology and Sequence Stratigraphy. SEPM Soc for Sed Geology. ISBN 9781565761162.
- ^ a b "Steep microbial boundstone-dominated platform margins—examples and implications". Sedimentary Geology. 178 (1–2): 5–30. 2005-07-01. doi:10.1016/j.sedgeo.2004.12.033. ISSN 0037-0738.