Artist's rendering of a trilobite based on preserved soft body parts.
Nobu Tamura
In my last blog post I wrote about the fact that Neanderthals were making marks, interpreted as art, on the wall of a French cave, 40,000 years before creationists believe Earth was created. This blog post is about creatures that lived much further into 'pre-Creation' history, some 490 million years 'pre-Creation' to be precise.
It's also about how the rocks in which their fossils were found were dated and how this means that fossils of these species can now be used to date other rocks, giving the lie to creationist claims that dating rock using 'index' fossils is circular reasoning. And dating those rock formations leads to a new understanding of the details of plate tectonics as the ancient continent, Gondwana, broke up.
Trilobites as a group are known to have diversified and diverged relatively quickly and became extinct relatively quickly too, so each species lived only for a few million years. This means, if we know when the species lived, we can date the rocks they are found in to within a few million years.
The fossils are of ten species of trilobite that are new to science which were found in layers of ancient volcanic ash between layers of sandstone in a little-studied area of Thailand. The ash layer forms greenish 'tuffs' which contains crystals of zircon produced during the volcanic eruption. Zircon crystals are extremely durable and remain unchanged embedded within the rocks. Trapped inside them are atoms of the radioactive isotopes of uranium, 238U and 235U, (both of which have very long half-lives and decay to stable isotopes of lead, which remains trapped within the zircon crystal lattice as a permanent record of what proportion of uranium has decayed to lead and which remain, giving a very precise date of the formation of the rock.
How can zircon crystals be used to date rocks? Zircon crystals are commonly used in radiometric dating to determine the age of rocks. This dating method is known as uranium-lead dating, and it relies on the radioactive decay of uranium isotopes. Here's a basic overview of how zircon crystals can be used for dating rocks:The precision and accuracy of uranium-lead dating with zircon crystals make it a valuable tool for dating rocks that are hundreds of millions to billions of years old. This method is particularly useful for dating the age of ancient rocks, including those in the Earth's crust and even the oldest rocks on Earth.
- Formation of Zircon Crystals: Zircon crystals often form in igneous rocks, such as granite, when molten magma solidifies. During the crystallization process, zircon crystals incorporate uranium atoms into their structure.
- Radioactive Decay: Uranium exists in two isotopic forms, uranium-238 (238U) and uranium-235 (235U). Both isotopes are radioactive and decay over time into lead isotopes. The decay is a predictable process with a known half-life. For 238U, the half-life is about 4.5 billion years, and for 235U, it is about 700 million years.
- Accumulation of Lead: As the zircon crystals form, they capture uranium in their crystal lattice. Over time, the uranium undergoes radioactive decay, transforming into lead isotopes. The lead isotopes are trapped within the crystal lattice.
- Measuring Uranium and Lead Content: Scientists can analyze the zircon crystals in a laboratory to measure the concentrations of uranium and lead isotopes. The ratio of parent uranium isotopes to daughter lead isotopes provides a measure of the age of the zircon crystal and, by extension, the age of the rock in which it formed.
- Calculation of Age: By comparing the amount of 238U and 235U in a zircon crystal to the amount of their respective decay products (lead isotopes), scientists can calculate the age of the crystal and, by inference, the age of the rock.
What isotopes of lead do the different isotopes of uranium decay to and are these also radioactive?
Uranium isotopes decay into lead isotopes through a series of radioactive decay steps. Here are the decay chains for uranium-238 (238U) and uranium-235 (235U):In summary, the lead isotopes resulting from the decay of uranium isotopes are stable and not radioactive. Lead-206 and lead-207 are the stable end products of the decay chains for uranium-238 and uranium-235, respectively. These stable lead isotopes do not undergo further radioactive decay.
- Uranium-238 Decay Chain:
All the lead isotopes in this decay chain, including lead-206, lead-210, and lead-214, are stable and not radioactive.
- 238U undergoes a series of decays and eventually transforms into stable lead-206 (206Pb).
- The decay steps involve several intermediate isotopes, including thorium-234 (234Th), protactinium-234m (234mPa), uranium-234 (234U), thorium-230 (230Th), radium-226 (226Ra), radon-222 (222Rn), polonium-218 (218Po), lead-214 (214Pb), bismuth-214 (214Bi), and polonium-214 (214Po).
- Uranium-235 Decay Chain:
Like in the 238U decay chain, all the lead isotopes produced in the decay of 235U, including lead-207, are stable.
- 235U decays into stable lead-207 (207Pb).
- Similar to 238U, the decay involves intermediate isotopes such as thorium-231 (231Th), protactinium-231 (231Pa), actinium-227 (227Ac), thorium-227 (227Th), radium-223 (223Ra), radon-219 (219Rn), polonium-215 (215Po), lead-215 (215Pb), bismuth-215 (215Bi), and polonium-211 (211Po).
The fossils were uncovered on the coast of an island called Ko Tarutao, and as well as the ten new species, there were 12 other species that are fund in other parts of the world, but never before found in Thailand.
The scientists describe their discovery in an open access paper in Papers in Palaeontology and in a press release from UC Riverside.
We can use radio isotope techniques to date when the zircon formed and thus find the age of the eruption, as well as the fossil. Not many places around the world have this. It is one of the worst dated intervals of time in Earth’s history.
What we have here is a chronicle of evolutionary change accompanied by extinctions. The Earth has written this record for us, and we’re fortunate to have it. The more we learn from it the better prepared we are for the challenges we’re engineering on the planet for ourselves today.
Because continents shift over time, part of our job has been to work out where this region of Thailand was in relation to the rest of Gondwanaland. It’s a moving, shape shifting, 3D jigsaw puzzle we’re trying to put together. This discovery will help us do that.
Nigel C. Hughes, co-corresponding author
Department of Earth & Planetary Sciences
University of California, Riverside, CA, USA.
Department of Earth & Planetary Sciences
University of California, Riverside, CA, USA.
The tuffs will allow us to not only determine the age of the fossils we found in Thailand, but to better understand parts of the world like China, Australia, and even North America where similar fossils have been found in rocks that cannot be dated.
Shelly Wernette, first author
Department of Earth & Planetary Sciences
University of California, Riverside, CA, USA
Now at Department of Geography & Environmental Studies
Texas State University, San Marcos, TX, USA
Department of Earth & Planetary Sciences
University of California, Riverside, CA, USA
Now at Department of Geography & Environmental Studies
Texas State University, San Marcos, TX, USA
For example, take the species named for Royal Princess Sirindhorn. The species was named in tribute to the princess for her steadfast dedication to developing the sciences in Thailand. If researchers can get a date from the tuffs containing her namesake species, Tsinania sirindhornae, and determine when they lived, they will be able to say that closely related species of Tsinania found in northern and southern China are roughly the same age.
AbstractFor creationists to ignore, there is firstly, the fact that these trilobites were around almost 490 million years pre-'Creation Week', there is also the fact that the dating method the scientists used to make them useful as index fossils for dating other rock formations exposes the lie that using index fossils is circular reasoning - the fossils were dated using tried the tired and tested 'zirconium' crystal method described in detail above. Creationists also need to ignore the fact that the dating method confirmed what was already known about when trilobites lived - what is the probability of these fossils just happening to be in rocks which could be independently dated to the time when trilobites are known to have lived?
Tuff-bearing upper Cambrian to lowermost Ordovician strata on Ko Tarutao island, Satun province, southernmost peninsular Thailand, contain a rich trilobite fauna relevant to global biostratigraphy, peri-Gondwanan palaeogeography and shifting evolutionary mode. This area of Sibumasu, a lower Palaeozoic marginal Gondwanan terrane, is shown to have been closely associated with Australia, North China (Sino-Korea) and other continental fragments from the supercontinent's northern equatorial sector, including South China at that time. Shared faunas also suggest a Kazakhstani and Laurentian association. Collections from eight sections yielded 10 newly discovered species and one new genus from ancient shoreface and inner shelf siliciclastic deposits. With the new taxa and revision of taxa known previously, we refine the age of the upper two formations of the Tarutao Group to the middle of Cambrian Stage 10, and lower–middle Tremadocian. Two biozones are erected for Sibumasu: the Eosaukia buravasi Zone, encompassing all Cambrian sections from Ko Tarutao, and the Asaphellus charoenmiti Zone, encompassing the Tremadocian fauna discussed herein. The new genus is Tarutaoia and new species are Tsinania sirindhornae, Pseudokoldinioidia maneekuti, Pagodia? uhleini, Asaphellus charoenmiti, Tarutaoia techawani, Jiia talowaois, Caznaia imsamuti, Anderssonella undulata, Lophosaukia nuchanongi and Corbinia perforata. Other taxa reported for the first time from Tarutao are Mansuyia? sp., Parakoldinioidia callosa Qian, Pseudagnostus sp., Homagnostus sp., Haniwa mucronata Shergold, Haniwa sosanensis? Kobayashi, Lichengia simplex Shergold, Pacootasaukia sp., Wuhuia? sp., Plethopeltella sp., Apatokephalus sp., Akoldinioidia sp. 1 and Koldinioidia sp.
Wernette, S.J., Hughes, N.C., Myrow, P.M. and Sardsud, A. (2023),
Trilobites of Thailand's Cambrian–Ordovician Tarutao Group and their geological setting.
Pap Palaeontol, 9: e1516. https://doi.org/10.1002/spp2.1516
Copyright: © 2023 The authors.
Published by John Wiley & Sons, Inc. Open access
Reprinted under a Creative Commons Attribution 4.0 International license (CC BY 4.0)
The tradition way that creationists cope with this sort of evidence that Earth is much older than their cult tells them, is to assert with no evidence whatsoever that radioactive decay rates used to be different and have changed over time, although they refuse to say whether that means they have speeded up or slowed down because none of them understand how dating is done or what a half-life is.
However, to change radioactive decay rates would involve changing two of the four fundamental forces - the weak and strong nuclear forces, the random quantum fluctuations of which determine radioactive decay - yet creationists also argue at other times that the Universe is so finely tuned for life that it must have been designed by their magic god, and changing even one of the 'parameters' by the smallest amount would make life impossible, so, if radioactive decay rates were different by an order of magnitude that makes 10,000 years look like 490 million years, then by their own argument, life would have been impossible when it was supposedly created.
Trilobites ruled the Paleozoic Era and came in different sizes. They were aquatic to amphibious. The early to middle Paleozoic Era had less oxygen than today. The Cambrian period, the Ordovician period, the Silurian period, and the Devonian period had oxygen levels below 21 percent while the late Paleozoic Era, which is the Carboniferous period and the Permian period, had abundant oxygen levels until the late Permian period 251 million years ago which had a mass extinction.
ReplyDeleteTrilobites had enemies mostly in the water. There were arachnids such as Eurypterids or Sea Scorpions which hunted them. Sea Scorpions came in various sizes and were up to 8 feet long, sporting monstrous claws.
There were also monstrous fish during the Paleozoic Era and mollusks such as Nautiloids which may have eaten Trilobites.
The true Scorpions also evolved during the Paleozoic Era and equipped with venomous stings. Scorpions continue to exist today and kill thousands of people a year in Mexico, Africa, and Asia. The earliest Scorpions came from the water and appeared roughly 435 million years ago during the Silurian period. One of the largest true Scorpions was Bronto Scorpio from the Devonian period which was a meter long and with a huge stinger. It would have made a meal of Trilobites and any small fish and early Insect it could catch.
Other dangerous predators on land during the Paleozoic Era would be primitive spiders and primitive centipedes and primitive amphibians. Predation is very old in the animal kingdom and could be as old as 540 million years ago during the Cambrian period when the first aquatic predator known as Anomalocaris appeared. This is hundreds of millions of years before the creation week in Genesis.