Lau event
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The Lau event was the last of three relatively minor
Biological impact
The Lau event started at the beginning of the late
Isotopic effects
A peak in δ13C, accompanied by fluctuations in other isotope concentrations, is often associated with mass extinctions. Some workers have attempted to explain this event in terms of climate or sea level change – perhaps arising due to a build-up of glaciers;[10] however, such factors alone do not appear to be sufficient to explain the events.[11] An alternative hypothesis is that changes in ocean mixing were responsible. An increase in density is required to make water downwell; the cause of this densification may have changed from hypersalinity (due to ice formation and evaporation) to temperature (due to water cooling).[9] A different hypothesis attributes the carbon isotope fluctuations to methanogenesis caused by the increased influx of iron-bearing dust and consequent disruption of limiting nutrient ratios.[12] Loydell suggests many causes of the isotopic excursion, including increased carbon burial, increased carbonate weathering, changes in atmospheric and oceanic interactions, changes in primary production, and changes in humidity or aridity. He uses a correlation between the events and glacially induced global sea level change to suggest that carbonate weathering is the major player, with other factors playing a less significant role.[6]
The δ13C curve slightly lags conodont extinctions, hence the two events may not represent the same thing. Therefore, the term Lau event is used only for the extinction, not the following isotopic activity, which is named after the time period in which it occurred.[6]
A positive excursion of δ34S in pyrite coincides with the positive δ13C excursion following the Lau event, likely related to the expansion of euxinic conditions and enhanced pyrite burial.[5][13]
Sedimentological impact
Profound sedimentary changes occurred at the beginning of the Lau event; these are probably associated with the onset of
These changes appear to display
See also
Further reading
References
- .
- .
- ^ "Chart/Time Scale". www.stratigraphy.org. International Commission on Stratigraphy.
- ^ The Ireviken, Mulde, and Lau events, were all closely followed by isotopic excursions.
- ^ . Retrieved 16 October 2022.
- ^ S2CID 128822111.
- .
- ^ Jeppsson, L. (1998). "Silurian oceanic events: summary of general characteristics". In Landing, E.; Johnson, M.E. (eds.). Silurian Cycles: Linkages of Dynamic Stratigraphy with Atmospheric, Oceanic and Tectonic Changes. James Hall Centennial Volume. New York State Museum Bulletin. Vol. 491. pp. 239–257.
- ^ S2CID 129255983. Retrieved 2007-06-26.
- ^ Lehnert, O.; Joachimski, M.M.; Fryda, J.; Buggisch, W.; Calner, M.; Jeppsson, L.; Eriksson, M.E. (2006). "The Ludlow Lau Event-another Glaciation In The Silurian Greenhouse?". Geological Society of America Abstracts with Programs. 2006 Philadelphia Annual Meeting. Vol. 38. p. 183. Archived from the original on 2008-03-17. Retrieved 2007-06-26.
- ]
- . Retrieved 26 December 2022.
- S2CID 219438899. Retrieved 16 October 2022.
- S2CID 129946754.
- doi:10.1130/G21185.1.