The Steptoean Positive Carbon Isotope Excursion (SPICE) was a geological event which occurred about 494.6 million years ago near the beginning of the International Furongian Epoch of the

Cambrian The Cambrian Period ( ; sometimes symbolized C with bar, Ꞓ) was the first geological period of the Paleozoic Era, and of the Phanerozoic Eon. The Cambrian lasted 53.4 million years from the end of the preceding Ediacaran Period 538.8 million ...

Period. The SPICE event was a positive shift in carbon isotope ( δ¹³C) values which lasted for around 2 to 4 million years. This shift is interpreted to be a global disturbance in the carbon cycle, affecting both the ocean and atmosphere. Regional sea level changes, a rise in sea water temperatures, ocean anoxia, and trilobite and brachiopod extinctions are associated with the SPICE event, although the exact mechanism(s) driving these events is still unconfirmed. One proposed cause of the SPICE is an increase in the burial of organic carbon, perhaps caused by increased primary productivity or enhanced organic matter preservation due to ocean deoxygenation (i.e.

anoxia The term anoxia means a total depletion in the level of oxygen, an extreme form of hypoxia or "low oxygen". The terms anoxia and hypoxia are used in various contexts: * Anoxic waters, sea water, fresh water or groundwater that are depleted of di ...

or euxinia). The spread of seafloor anoxia has also been proposed as the kill mechanism for the extinctions of marine organisms.

References

{{reflist Events that forced the climate Cambrian events