The Geologic Column

The geologic column is the standard sequence of rock units and the time periods they represent. It was assembled during the nineteenth century by correlating strata between regions using faunal succession, before radiometric dating existed.

The periods are named after the places where they were first described — Devonian from Devon, Jurassic from the Jura mountains, Cambrian from the Roman name for Wales. The names are geographic accidents rather than a theoretical scheme.

The column#

Boundaries are defined by the International Commission on Stratigraphy at specific physical locations — a Global Boundary Stratotype Section and Point, or "golden spike," driven into an actual outcrop. The current chart is published and revised as boundaries are refined.

Where complete sequences exist#

The claim that the full column exists nowhere is common in young-earth literature. It depends on what "complete" means.

No single outcrop contains every period, because no location has been continuously subsiding and receiving sediment for 4.5 billion years. Any given place spends time above sea level, eroding rather than depositing.

Sedimentary basins with continuous subsidence do contain long unbroken sequences. Sections containing all ten Phanerozoic periods are documented in:

Glenn Morton, a geophysicist who worked in petroleum exploration and was formerly a young-earth creationist, published borehole data from several of these while arguing against the claim that complete sections do not exist. Drilling logs are commercial records generated to find oil, and the companies producing them have no stake in the age question.

Why the column is not circular#

The order came first, from faunal succession — the observation that fossil assemblages occur in a consistent vertical sequence wherever they are found. William Smith mapped this in England by 1815.

Absolute ages were added from the 1900s onward by radiometric dating of igneous rocks: volcanic ash beds interbedded with sediment, and intrusions cutting across it. These dates come from decay systems that have nothing to do with fossils.

The two agree. The sequence radiometric dating produces is the sequence Smith established from fossils a century earlier, which would be a considerable coincidence if either were arbitrary.

What would break it#

The column makes a strong negative prediction: certain fossils should never occur below certain levels.

• No flowering plants below the Cretaceous
• No mammals below the Triassic
• No land vertebrates below the Devonian
• No vertebrates at all below the Cambrian
• No rabbits in the Precambrian, in J. B. S. Haldane's formulation

Millions of specimens have been catalogued across every continent since the 1800s, by commercial, academic, and amateur collectors. No verified exception has been found.

Common objections#

"The complete column exists nowhere on earth"

Frequently stated, and true for a single surface outcrop.

It is not true for the subsurface. Boreholes in the basins listed above pass through all ten Phanerozoic periods in order, and the logs are public or commercially available.

The claim also proves less than intended. If the column existed only as a correlation between regions, that correlation would still require explanation — the same fossil assemblages occurring in the same relative order on separate continents is the observation, whether or not any one place preserves all of it.

"The column is a hydrodynamic sorting of animals drowned in the flood"

The main young-earth alternative: denser or bottom-dwelling organisms settled first, then more mobile animals, then those that fled to higher ground.

It makes testable predictions, and they fail in specific ways.

Sorting by density or size does not produce the observed order. Many Cambrian trilobites are larger than Cenozoic mammals. Delicate ammonites are found intact above robust dinosaur bone. Flowering plants — light, buoyant, and abundant — appear only from the Cretaceous, above thousands of metres of strata.

The pollen problem is acute. Pollen grains are microscopic and disperse in water, so they should appear throughout. Angiosperm pollen is absent below the Cretaceous.

Ecological zonation fares no better: whales and dolphins are marine mammals that would sort with fish under any hydrodynamic model, and are found only in Cenozoic rock.

"Polystrate fossils show the layers formed at once"

Covered separately in Polystrate Fossils. In brief: upright trunks crossing several layers are found within single depositional units of a few metres, in settings — river deltas and coal swamps — where rapid burial of individual sites is expected and documented.

They do not cross period boundaries, which is what the objection would require.

"Index fossils are chosen circularly to give the desired dates"

Index fossils are chosen for practical properties: wide geographic distribution, short time range, abundance, and distinctive form.

The short time range is the point at issue and is not assumed. It is measured by finding where the organism occurs relative to other markers and to datable volcanic layers, and the range is revised when specimens are found outside it — as with the coelacanth, thought extinct since the Cretaceous until a living one was caught in 1938.

The coelacanth case is instructive: its range was corrected rather than the discovery being suppressed, and it did not disturb the column, since the fossil coelacanths remained where they were.

What the evidence shows#

The column is a composite built from overlapping regional sequences correlated by fossil content, and complete Phanerozoic sections are documented in several subsiding basins.

Its order was established from fossils before radiometric dating existed, and the dating agreed with it when applied.

The order makes strong negative predictions that have survived roughly two centuries of collecting. The main alternative, hydrodynamic sorting during a flood, predicts an order determined by density, size, and mobility, and the observed order does not follow those variables.