Global Boundary Stratotype Section and Point in the context of "Rhaetian"

The Ediacaran ( /ˌiːdiˈækərən, ˌɛdi-/ EE-dee-AK-ər-ən, ED-ee-) is a geological period of the Neoproterozoic Era that spans 96 million years from the end of the Cryogenian Period at 635 Mya to the beginning of the Cambrian Period at 538.8 Mya. It is the last period of the Proterozoic Eon as well as the last of the so-called "Precambrian supereon", before the beginning of the subsequent Cambrian Period marks the start of the Phanerozoic Eon, where recognizable fossil evidence of life becomes common.

The Ediacaran Period is named after the Ediacara Hills of South Australia, where trace fossils of a diverse community of previously unrecognized lifeforms (later named the Ediacaran biota) were first discovered by geologist Reg Sprigg in 1946. Its status as an official geological period was ratified in 2004 by the International Union of Geological Sciences (IUGS), making it the first new geological period declared in 120 years. Although the period took namesake from the Ediacara Hills in the Nilpena Ediacara National Park, the type section is actually located in the bed of the Enorama Creek within the Brachina Gorge in the Ikara-Flinders Ranges National Park, at 31°19′53.8″S 138°38′0.1″E / 31.331611°S 138.633361°E / -31.331611; 138.633361, approximately 55 km (34 mi) southeast of the Ediacara Hills fossil site.

An anoxic event describes a period wherein large expanses of Earth's oceans were depleted of dissolved oxygen (O₂), creating toxic, euxinic (anoxic and sulfidic) waters. Although anoxic events have not happened for millions of years, the geologic record shows that they happened many times in the past. Anoxic events coincided with several mass extinctions and may have contributed to them. These mass extinctions include some that geobiologists use as time markers in biostratigraphic dating. On the other hand, there are widespread, various black-shale beds from the mid-Cretaceous which indicate anoxic events but are not associated with mass extinctions. Many geologists believe oceanic anoxic events are strongly linked to the slowing of ocean circulation, climatic warming, and elevated levels of greenhouse gases. Researchers have proposed enhanced volcanism (the release of CO₂) as the "central external trigger for euxinia."

Human activities in the Holocene epoch, such as the release of nutrients from farms and sewage, cause relatively small-scale dead zones around the world. British oceanologist and atmospheric scientist Andrew Watson says full-scale ocean anoxia would take "thousands of years to develop." The idea that modern climate change could lead to such an event is also referred to as Kump's hypothesis.

In the geologic time scale, the Greenlandian is the earliest age or lowest stage of the Holocene Epoch or Series, part of the Quaternary. Beginning in 11,650 BP (9701 BCE or 300 HE) and ending with the 8.2-kiloyear event (c. 8200–8300 BP, 6200–6300 BCE, 3600–3700 HE), it is the earliest of three sub-divisions of the Holocene. It was officially ratified by the International Commission on Stratigraphy in June 2018 with the later Northgrippian and Meghalayan Ages/Stages. The lower boundary of the Greenlandian Age is the GSSP sample from the North Greenland Ice Core Project in central Greenland (75.1000°N 42.3200°W). The Greenlandian GSSP has been correlated with the end of Younger Dryas (from near-glacial to interglacial) and a "shift in lower deuterium excess values".

The Ikara–Flinders Ranges National Park, formerly Flinders Ranges National Park, is a national park situated approximately 430 km (270 mi) north of Adelaide, Australia. It lies northeast of the small town of Hawker, in the northern central part of South Australia's largest mountain range, the Flinders Ranges, and covers an area of 95,000 ha (370 sq mi) between Hawker and Blinman. It is known for the land formation known as Wilpena Pound, while other well-known features include the Heysen Range and the Brachina and Bunyeroo gorges. The Heysen Trail and Mawson Trail pass through the park.

The whole park is part of the Flinders Ranges geological successions, where abundant and diverse arrays of fossils show how animal life began on Earth over a period of 350 million years. Within the park, on Enorama Creek, there is a Global Boundary Stratotype Section and Point (GSSP, or "Golden Spike"), ratified by the International Commission on Stratigraphy in 2004. The GSSP defines the lower boundary of the Ediacaran period, then recently recognised for the first time. As well as containing a large number of heritage-listed sites, Ikara–Flinders Ranges National Park is one of a group of seven geographically separate areas that were submitted to the UNESCO World Heritage Centre for consideration as a World Heritage Site in 2021, and as of August 2025 remain on the tentative list.

The Tremadocian is the lowest stage of Ordovician. Together with the later Floian Stage it forms the Lower Ordovician Epoch. The Tremadocian lasted from 486.85 to 477.1 million years ago. The base of the Tremadocian is defined as the first appearance of the conodont species Iapetognathus fluctivagus at the Global Boundary Stratotype Section and Point (GSSP) section on Newfoundland.