Sub-stage· The columns of time

Northgrippian

6,237 BCE → 2,251 BCE

The Northgrippian is the second age of the Holocene, from 8,200 to 4,200 years ago.

Second age of the Holocene, running from 8,200 to 4,200 years before present. The first cities, writing, metallurgy and the first state organisations appear within this interval, independently of one another in several regions.

What the evidence shows

The age takes its name from the North Greenland Ice Core Project, the drilling programme whose ice supplies its lower reference point, at 8,200 years before present; the upper limit, at 4,200 years, is defined in an Indian speleothem. It contains most of what a history of civilisations enumerates at its opening, a coincidence following from the placement of geological markers and not from a causal relation. The two disciplines divide the same time on distinct criteria, and their divisions rarely coincide.

Bounds and conventions

The age is defined by ice chemistry and not by human events. Its lower limit is an abrupt climatic signal recorded in Greenland and its upper limit a drought episode recorded in India; the appearance of the first cities within this interval implies no causal relation.

GSSP NGRIP1, 8,236 years b2k, an abbreviation of before 2000: glaciologists count from the year 2000, their cores being numbered in annual layers from the top, whereas radiocarbon counts from 1950. Those fifty years of difference, negligible over eleven millennia, explain why two disciplines give a single limit two slightly different numbers.