The Shuram excursion, or Shuram-Wonoka excursion, is a change in δ13C, or in the ratio of carbon-13 to carbon-12, taking place during the Ediacaran Period. The exact time period of the excursion is debated among scholars, beginning around 573 Ma and ending around 562[1] or 551[2] Ma. It was first noticed in the Wonoka Formation in South Australia in 1990 and later in the Shuram Formation in Oman in 1993.[3] It is the largest negative δ13C excursion in Earth history, and recovery took 50 million years,[4] although the apparent magnitude of the excursion may be distorted due to meteoric water diagenesis.[5]
It is not known what caused the excursion.[6] The Shuram excursion may have played a role in sparking the rise of animals that resulted later in the Cambrian explosion.[7] The oxygen-consuming Ediacara biota experienced a radiation during the isotopic excursion as a response to the transient surplus of oxidants.[8]Microbial blooms of oxygenic phototrophs regulated the recovery of the carbon cycle from the isotopic excursion.[9]