from a cave in the Indian state of Meghalaya that helped define climatic events 4,200 years ago, marking the beginning of the phase that continues till today.
Two other ages — the Middle Holocene Northgrippian Age and the Early Holocene Greenlandian Age — with beginnings defined at climatic events that happened about 8,300 years and 11,700 years ago, respectively, were also approved by the International Commission on Stratigraphy, which is responsible for standardising the geologic time scale.
These units of the geologic time scale are based on sedimentary strata that have accumulated over time and contain within them sediment types, fossils and chemical isotopes that record the passage of time as well as the physical and biological events that produced them.
The lower boundary of the Greenlandian and Northgripppian stages are defined at specific levels in Greenland ice cores.
The lower boundary of the Meghalayan stage is defined at a specific level in a stalagmite from a cave in the northeastern Indian state.