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Lau event
The Lau event was the last of three relatively minor mass extinctions during the Silurian period,〔The Ireviken event and Mulde event, other late Silurian extinction events, were both closely followed by isotopic excursions as was the Lau event.〕 having a major effect on the conodont fauna (but barely scathing the graptolites). It coincided with a global low point in sea level, is closely followed by an excursion in geochemical isotopes in the ensuing late Ludfordian faunal stage and a change in depositional regime.
==Biotic impact==
The Lau event started at the beginning of the late Ludfordian, a subdivision of the Ludlow stage, about . Its strata are best exposed in Gotland, Sweden, taking its name from the parish of Lau. Its base is set at the first extinction datum, in the Eke beds, and despite a scarcity of data, it is apparent that most major groups suffered an increase in extinction rate during the event; major changes are observed worldwide at correlated rocks, with a "crisis" observed in populations of conodonts and graptolites.〔
〕 More precisely, conodonts suffered in the Lau event, and graptolites in the subsequent isotopic excursion.〔 Local extinctions may have played a role in many places, especially the increasingly enclosed Welsh basin; the event's relatively high severity rating of 6.2 does not change the fact that many life-forms became re-established shortly after the event, presumably surviving in refuge or in environments that have not been preserved in the geological record. Although life persisted after the event, community structures were permanently altered and many lifeforms failing to regain the niches they had existed in prior to the event.
抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』
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