The Cambrian Golden Spike Sits Four Metres Above Its Own Fossil
The Cambrian — and the whole eon we live in — officially begins at one point in a sea cliff in Newfoundland, at the first appearance of a single burrow. In 1999 the same burrow was found 4.41 metres below the point. And the point has never been dated: every published age for the start of the Cambrian was measured somewhere else, and it has moved eleven million years in thirty.
Chapters
- 0:00 Nothing dug
- 0:21 Fortune Head, Newfoundland
- 0:46 What a golden spike does
- 1:09 440 m of the Chapel Island Formation
- 1:35 For a century, a trilobite
- 2:02 Twenty years to one point
- 2:24 Three candidate sections
- 2:49 The postal ballot of 1991
- 3:13 Why a burrow, and not a shell
- 3:41 Treptichnus pedum
- 4:11 The section as ratified
- 4:36 Summer 1999: 4.41 metres below
- 5:06 Skolithos, Gyrolithes, GSC 116870
- 5:37 The ranges overlap
- 6:05 Namibia: 450 m below the Ediacaran fauna
- 6:36 Matgrounds above the spike
- 7:09 The spike has never been dated
- 7:32 544, 541, 538.8, 532.8
- 8:05 A burrow is not a clock
- 8:39 The 2014 reassessment call
- 9:10 What survives
- 9:36 The line is ours
- 10:02 Next: Mistaken Point
Transcript
Nothing dug 0:00
For most of the history of life, nothing dug. The sea floor was a skin. Mats of microbes sealed the sediment, and whatever lived on top of them stayed on top. Then something pushed down into the mud, turned, and pushed again. The mark it left is where the Cambrian officially begins.
Fortune Head, Newfoundland 0:21
This is Fortune Head, on the Burin Peninsula of Newfoundland. In the cliffs below this lighthouse, a single kind of burrow marks the base of the Cambrian Period. It is the golden spike: the one point on Earth that defines the start of the period, the start of the Paleozoic, and the start of the eon we still live in. And the same burrow turns up four metres below the spike.
What a golden spike does 0:46
A golden spike is a point in rock chosen to define a moment in time. Everywhere else on the planet, a geologist has to find something in their own rocks that lines up with it. That is what makes a period a period, and not just a name. So the choice of spike is not decoration. It decides what counts as Cambrian on every continent.
440 m of the Chapel Island Formation 1:09
Under the lighthouse, four hundred and forty metres of the Chapel Island Formation dip into the sea. Silt and sand, laid on a shallow shelf, now tilted west at fifteen to forty six degrees. Read from the bottom, the beds cross the boundary without a break in deposition and without a change in environment. That was the point. Nothing here jumps except the fossils.
For a century, a trilobite 1:35
For a century, the base of the Cambrian was a trilobite. Charles Walcott set it at the Olenellus Zone in eighteen ninety, and that is roughly where textbooks left it until the late nineteen forties. At Fortune Head, the first trilobites appear about one thousand four hundred metres above the spike. The first shells appear about four hundred metres above it. The boundary was pushed a long way down.
Twenty years to one point 2:02
The pushing took twenty years. A working group formed in Montreal in nineteen seventy two. In Paris, two years later, it agreed on three rules. The Ediacara-type fauna is Precambrian. The oldest trilobites are Cambrian. Everything in between was the problem it had to solve.
Three candidate sections 2:24
By nineteen eighty three there were three candidate sections. One on the Aldan River in eastern Siberia, in limestone full of tiny shelly fossils. One at Meishucun in Yunnan, southern China, in phosphate rock. And several cliffs on the Burin Peninsula of Newfoundland, where only outline studies existed and no exact point had been picked.
The postal ballot of 1991 2:49
In the spring of nineteen ninety one the twenty three voting members were balloted by post. Fifty two percent chose Newfoundland, thirty five percent China, thirteen percent Siberia. A second ballot on the Burin section alone reached sixty one percent. The International Union of Geological Sciences ratified it in Kyoto in August nineteen ninety two.
Why a burrow, and not a shell 3:13
Why a burrow, and not a shell? Because the small shelly fossils had turned out to be provincial. They lived in shallow carbonate seas, and their order of appearance changed from one region to the next. Trace fossils are the opposite. They are common in sand and silt, which make up nearly seventy percent of the exposed rock of this age. And around the world they appeared in the same order.
Treptichnus pedum 3:41
The chosen fossil is Treptichnus pedum. It is preserved as branched ridges on the underside of a sandstone bed. An animal probed forward through the sediment, backed up, and probed again, leaving a chain of curved segments. Experiments in twenty ten matched it to priapulid worms, a group that is still alive today. What matters for the boundary is the shape. It is a three-dimensional burrow, and in nineteen ninety two that was taken to be new.
The section as ratified 4:11
Here is the measured section. The spike sits two point four metres above the base of Member two, at twenty point six six metres in the log. Below it, Member one carries the last of the Precambrian traces, Harlaniella podolica, last seen twenty centimetres under the spike. Above it, within three metres, the Cambrian burrows arrive one after another.
Summer 1999: 4.41 metres below 4:36
In the summer of nineteen ninety nine, a team including two of the geologists who had described the section came back and logged it at centimetre scale. They found Treptichnus pedum at sixteen point two five metres, and again at seventeen point five five. That is four point four one metres and three point one one metres below the golden spike. Both specimens are in the top of Member one. Below the last Harlaniella.
Skolithos, Gyrolithes, GSC 116870 5:06
It was not only the index fossil. Skolithos, the vertical tube burrow, and Gyrolithes, the spiral one, both supposed to begin in the Cambrian zone, were found two and a half metres below the spike. Simpler zigzag Treptichnus burrows were found between eleven and thirteen metres below it. And the specimen from three metres down was collected. It is catalogued at the Geological Survey of Canada as G S C one one six eight seven zero.
The ranges overlap 5:37
The decision paper of nineteen ninety four had said, in so many words, that the ranges of Harlaniella and Treptichnus pedum were believed not to overlap. One succeeds the other. That clean replacement was one of the reasons Fortune Head won. Five years later the ranges overlapped by four metres. Not because the rock changed. Because somebody looked closer, in better light.
Namibia: 450 m below the Ediacaran fauna 6:05
And Fortune Head is not the only place where the marker runs early. In Namibia, Treptichnus burrows occur in the Nama Group four hundred and fifty metres below the youngest Ediacaran body fossils. The burrow style that the Cambrian is defined by was already being made under the feet, so to speak, of the Precambrian fauna. The nineteen seventy four rule said Ediacara-type fauna is Precambrian. In Namibia the rock has the burrows first, and the fauna on top of them.
Matgrounds above the spike 6:36
The picture above the spike is just as untidy. In twenty fourteen a study of the type section found the old Ediacaran-style sea floor, the microbial matgrounds and their simple traces, persisting well into the Cambrian beds. Ediacara-type body fossils are present immediately below the boundary and absent above it. What replaces them on the mats is the first abundant arthropod scratch marks on Earth. The ecology changed in steps. The line is one moment.
The spike has never been dated 7:09
Now the part almost nobody mentions. The golden spike has never been dated. There is no volcanic ash at the boundary, no carbonate suitable for carbon or strontium isotopes, and the whole section was remagnetised in the Ordovician. Every number you have ever seen for the start of the Cambrian was measured somewhere else and carried here by correlation.
544, 541, 538.8, 532.8 7:32
Watch the number move. In nineteen ninety four the decision paper estimated about five hundred and forty four million years, from volcanic rock in Siberia. In two thousand and seven an ash bed in Oman gave five hundred and forty one. In twenty nineteen ash beds in Namibia bracketed it at five hundred and thirty eight point eight, which is the number on the official chart today. In twenty twenty three, zircons from Nevada put the first Treptichnus pedum there at or below five hundred and thirty two point eight.
A burrow is not a clock 8:05
Each of those dates is honest. Each one dates the same fossil, or the same chemical signal, in a different basin. And they do not agree, because a burrow is not a clock. It appears when the animal arrives, and the animal arrived in different places at different times. The twenty twenty six review by Bowyer and Nelson puts the boundary somewhere between five hundred and thirty eight and five hundred and thirty three million years. Five million years of uncertainty, on the most important line in the fossil record.
The 2014 reassessment call 8:39
So in twenty fourteen five stratigraphers from three continents proposed a formal reassessment. Their case: the spike correlates poorly to Siberia and to South China, the two regions with the richest early Cambrian record. And the point sits above the first appearance of its own fossil. Their options ran from doing nothing, to moving the point, to choosing a new section altogether. No decision has been taken. The spike still stands.
What survives 9:10
What survives? The nineteen ninety nine team did not ask for the spike to be pulled. They wrote that Treptichnus pedum remains a reasonable indicator, and that the point still marks a level above the last Harlaniella and below the burst of new burrows. That is what a boundary in a gradual record can be. A convention, placed with care, inside a transition that took millions of years.
The line is ours 9:36
A golden spike is a point in rock that defines a moment in time. That is the wording of the decision itself. The point has not moved a centimetre since nineteen ninety two. The moment has moved eleven million years in thirty. And the fossil that was supposed to arrive at the point arrives below it. The line is ours. The rock only records what happened.
Next: Mistaken Point 10:02
Next time, the same island, two hundred kilometres east. At Mistaken Point, the oldest large complex organisms on Earth lie under a fall of volcanic ash, five hundred and sixty five million years old. They lived far below the reach of sunlight. And the ash that killed them is the only reason we can date them.
Description and sources
The GSSP at Fortune Head, Newfoundland, sits 2.4 m above the base of Member 2 of the Chapel Island Formation, at the first appearance of Treptichnus pedum, ratified in 1992 after a twenty-year working group and a postal ballot (52% Newfoundland, 35% China, 13% Siberia). In 1999 Gehling, Jensen, Droser, Myrow and Narbonne logged the section at centimetre scale and found T. pedum 4.41 and 3.11 m below the spike (specimen GSC 116870), Skolithos and Gyrolithes 2.51 m below, and zigzag Treptichnus 11 to 13 m below — where the 1994 decision said the ranges did not overlap. The spike has no ash bed, no suitable carbonate and was remagnetised in the Ordovician: its published age has moved from about 544 Ma (1994) to 541.0 (Oman, 2007), 538.8 (Namibia, 2019) and 532.8 or younger (Nevada, 2023, contested). A 2014 reassessment proposal is still open.
PRINT-READY, FROM THIS CHANNEL
The Deep Time Record, Vol. 01 — the cores, the curves and the clocks
https://therepository.gumroad.com/l/deep-time-record
PRIMARY SOURCES
- Brasier, Cowie & Taylor 1994 — Decision on the Precambrian–Cambrian boundary stratotype. Episodes 17:3-8. https://stratigraphy.org/gssps/files/fortunian.pdf
- Gehling, Jensen, Droser, Myrow & Narbonne 2001 — Burrowing below the basal Cambrian GSSP, Fortune Head. Geol. Mag. 138:213-218. https://doi.org/10.1017/S001675680100509X
- Babcock, Peng, Zhu, Xiao & Ahlberg 2014 — Proposed reassessment of the Cambrian GSSP. J. Asian Earth Sci. 98:3-10. https://doi.org/10.1016/j.jafrearsci.2014.06.023
- Jensen, Saylor, Gehling & Germs 2000 — Complex trace fossils from the terminal Proterozoic of Namibia. Geology 28:143-146.
- Buatois et al. 2014 — Ediacaran matground ecology persisted into the earliest Cambrian. Nat. Commun. 5:3544. https://doi.org/10.1038/ncomms4544
- Vannier et al. 2010 — Priapulid worms: pioneer horizontal burrowers at the Precambrian–Cambrian boundary. Geology 38:711-714.
- Bowring et al. 2007 — Huqf Supergroup, Oman. Am. J. Sci. 307:1097.
- Linnemann et al. 2019 — New high-resolution age data from the Ediacaran–Cambrian boundary. Terra Nova 31:49-58. https://doi.org/10.1111/ter.12368
- Nelson et al. 2023 — Cambrian explosion condensed: geochronology of the lower Wood Canyon Formation, Nevada. PNAS 120:e2301478120. https://doi.org/10.1073/pnas.2301478120
- Bowyer & Nelson 2026 — Reviewing chronostratigraphic uncertainty of the Ediacaran–Cambrian transition. J. Geol. Soc. https://doi.org/10.1144/jgs2025-100
- ICS — GSSP for the Fortunian Stage. https://stratigraphy.org/gssps/fortunian
- Matthews et al. 2021 — A chronostratigraphic framework for the rise of the Ediacaran macrobiota, Mistaken Point. GSA Bull. 133:612-624. https://doi.org/10.1130/B35646.1
ARCHIVE IMAGES — 7, each credited on screen in the video with author and licence, and listed in this project's manifest.
The 3 generated plates were made for this channel with FLUX.1-schnell. No person is depicted in any of them.
Deep Time Archives rebuilds the pre-human Earth from the physical record — outcrops, drill cores, golden spikes, catalogued specimens. Every episode starts from an object you can go and check, and the sources are listed above.
About the images. Seven are archive photographs, credited on screen; none shows the Fortune Head outcrop itself (the photographs of that cliff online carry a share-alike licence this channel does not use). The lighthouse is the real Fortune Head. The burrowed sandstone and Dickinsonia are from South Australia, the Skolithos from Minnesota, the Kimberella from the White Sea — each says so on screen. The sea floor, the tidal flat and the rippled mat are AI-generated reconstructions; no animal in this video is generated. This video is labelled as containing altered or synthetic content. The diagrams are drawn in code from the published numbers.