Toolchest · Datasheet

Geologic Time Scale — Accumath Toolchest

Dataset: accumath-geologic-time-scale.csv — 170 rows: 4 eons, 10 eras, 22 periods, 34 epochs, 100 ages/stages.

Source and version

• Source: International Chronostratigraphic Chart, International Commission on Stratigraphy (ICS), IUGS — stratigraphy.org.
• Chart version used: v2026/06 (June 2026), the current edition as served by stratigraphy.org when downloaded on 2026-10-20 (ChronostratChart2026-06.pdf). Chart citation as printed on it: Cohen, K.M., Harper, D.A.T., Gibbard, P.L. & Car, N. (2025, updated), "The ICS international chronostratigraphic chart this decade," Episodes 48: 105–115.
• Ages were read from the chart PDF itself (positionally parsed from the official file), so names and ages pair exactly as drawn.

Conventions

• Ma = millions of years before present. start_Ma is the age of the unit's lower (older) boundary — the numerical age the chart prints at that unit — copied exactly, including the printed uncertainty (e.g. 251.902 ±0.024) and the chart's approximation marker (~) where the chart prints one.
• end_Ma is the unit's upper (younger) boundary, which is by definition the base age of the next younger unit; the numeric value only is carried here (the ~/± is recorded on the younger unit's own start_Ma row). The youngest units in each lineage (Meghalayan, Holocene, Quaternary, Cenozoic, Phanerozoic) end at present (0).
• Epoch/period/era/eon base ages equal the base age of their oldest constituent unit, as drawn on the chart.
• Subseries are not separate rows. The chart's Upper/Middle/Lower subseries (U/L, M, L/E) within epochs are not tabulated; one named exception worth knowing: the informal Upper Pleistocene subseries has a charted base of 0.129 Ma and no ratified stage name.
• Epoch names are given in their full form (e.g. "Upper Cretaceous"); the chart's Series column prints "Upper/Lower" beside the parent system.

Caveats (from the chart's own notes)

• Boundary ages are revised between chart editions. The chart states that numerical ages are subject to ongoing revision and do not define the units in the Phanerozoic and the Ediacaran — only the GSSPs do. These values are the v2026/06 edition's values and will drift in later editions. Most numerical ages are taken from A Geologic Time Scale 2020 (Gradstein et al. 2020), with some updated by the ICS subcommissions, per the chart's footnote.
• GSSP vs GSSA. Phanerozoic (and Ediacaran) unit bases are defined by Global Boundary Stratotype Sections and Points (GSSP). Archean and Proterozoic units were long defined by Global Standard Stratigraphic Ages (GSSA) — round chronometric ages (1000, 1200, 1600, 2500 Ma, …), which is why the Precambrian periods carry round-number bases with no uncertainty. Rows affected carry a note in GSSP_note.
• Approximate ages. Where the chart lacks a ratified GSSP or a constrained numerical age it prints an approximate age prefixed ~ (e.g. Norian ~227.3, most Cambrian Series 2 / Miaolingian / Furongian stages). Copied as printed.
• Placeholder names. Cambrian "Series 2", "Stage 2", "Stage 3", "Stage 4", and Furongian "Stage 10" are numbered placeholders for units whose formal names are not yet ratified; flagged per row.
• Pridoli (Silurian) is a series/epoch the chart does not subdivide into stages.
• Hadean is an informal eon with no formal subdivisions; the chart prints its base as 4567 Ma.

Legal basis

Values are the published facts of the ICS chart, recorded with the source and edition named on every row; no chart artwork, layout, or text is reproduced.