euxinia

Nitrogen cycle feedbacks as a control on euxinia in the mid-Proterozoic ocean.

The research suggests that previous estimates of oxygen-free and hydrogen sulfide-rich conditions, or "euxinia," were too high.

Researchers have proposed enhanced volcanism (the release of CO) as the "central external trigger for euxinia".

However, only "in rare, extreme cases, [did] euxinia lead to biotic crises."

These processes potentially acted as a trigger for euxinia in restricted basins where water-column stratification could develop.

Nevertheless, the limited and localized euxinia were still sufficiently widespread to have dramatic effect on the entire ocean's chemistry and thus biological activity.

Models of ocean chemistry show that anoxia and euxinia would have been closely associated with hypercapnia (high levels of carbon dioxide).

Hypercapnia best explains the selectivity of the extinction, but anoxia and euxinia probably contributed to the high mortality of the event.

This event has been related to glaciation in the temperate and polar zones as well as euxinia and anoxia in the seas.

During the Archean euxinia was largely absent because of low availability of sulfate in the oceans, but during the Proterozoic, it with would become more common.

Evidence for widespread ocean anoxia (severe deficiency of oxygen) and euxinia (presence of hydrogen sulfide) is found from the Late Permian to the Early Triassic.

The mechanisms by which organic matter accumulated within these sediments consisted of a complex interplay of local carbonate generation, clastic input from outside sources, variable burial rates, and variable bottom water anoxia and euxinia.

Biomarkers for green sulfur bacteria, such as isorenieratane, the diagenetic product of isorenieratene, are widely used as indicators of photic zone euxinia, because green sulfur bacteria require both sunlight and hydrogen sulfide to survive.