Revisiting the Spark of the Cambrian Explosion

The Cambrian explosion, a burst of rapid evolution that occurred 540 million years ago, may have been triggered by a slight increase in oxygen levels in Earth's atmosphere and shallow oceans, according to a study published July 2 in the journal Nature Geoscience by an international consortium of scientists from more than 50 institutions.

Cambrian animals likely didn't need as much oxygen as scientists once thought. “We found a small increase in oxygenation that was just enough to make a big difference in the ecosystem,” said Eric Sperling, an associate professor of Earth and planetary sciences at Stanford's Doerr School of Sustainability, who led the consortium.

The study reconciles conflicting data sets from around the world and provides the clearest evidence to date that there was only a small increase in oxygen around the time of the Cambrian explosion. Furthermore, the researchers also found evidence that deep-sea oxygen levels did not approach modern-day ocean levels until about 140 million years after the Cambrian explosion, much later than previously thought.

“There was at least some increase in atmospheric oxygen about 540 million years ago, which affected oxygen availability in shallow marine environments, where most marine biodiversity lives,” said lead study author Dr. Richard Stockey (22), a paleontologist at the University of Southampton who worked on the research as part of his doctoral thesis in Sperlings' research group at Stanford. But on a global scale, ocean oxygenation did not approach modern levels until about 400 million years ago, around the time large forests appeared on land.

Cambrian rocks from the Wall Formation in Jasper National Park, Alberta, Canada. Erik Sperling

Just the right amount of oxygen

For decades, scientists have theorized that the Cambrian explosion was caused by a sudden increase in atmospheric oxygen, bringing oxygen levels in ancient oceans closer to modern levels, but the evidence for this is scattered and sometimes contradictory.

“This is one of the big questions about evolution,” Sperling says. Over 4 billion years of evolutionary history, very little appears in the rock record, but then over the last 20 to 30 million years, there was an explosion of new body forms. In a geologic flash, animals evolved hard shells, primitive spines, and the precursors to the life forms we see today.

It seems Cambrian animals didn't need as much oxygen as scientists thought: we found a slight increase in oxygenation that was just enough to make a big difference to the ecosystem.

Eric Sperling, Associate Professor of Earth and Planetary Sciences

Although the researchers found that there was only a small increase in atmospheric oxygen at the time of the Cambrian explosion, it may not have taken much time to drive the evolutionary leaps seen in the fossil record: Most animals lived in shallow waters at the time, and even if the deep ocean remained unchanged, mixing by wind and waves would have provided oxygen to the shallows.

The increase in oxygen isn't huge, but it could be enough to push ecological limits, based on modern nature and conditions seen in low-oxygen regions, Sperling said.

Black shale from the Ediacarian Nadaleen Formation in the Yukon Territory, Canada. A consortium of scientists led by Stanford University studied the black shale record throughout geologic time and concluded that the oceans reached modern levels of oxygenation during the Devonian Period, around the time that land plants rapidly diversified. | Jared Gooley

Uncovering the Answers

To explore changes in oxygen over 700 million years of Earth's history, Stockey and Sperling looked at data showing levels of the metals uranium and molybdenum in black shale, a type of sedimentary rock that formed in low- or anoxic (oxygen-free) environments on the floor of ancient oceans.

In low-oxygen environments, these trace elements are pulled out of the seawater and accumulated in the sediments. If large areas of the ocean are anoxic, the amounts of molybdenum and uranium in the black shales should be low, because these rare metals are continually being pulled out of the seawater and buried over large areas. On the other hand, if only a few areas of the ocean are anoxic, the amounts of molybdenum and uranium in the seawater should be high, and they should be highly concentrated in the black shales.

Previous studies have found that concentrations of trace metals in black shales increase around the time of the Cambrian explosion. But other signals can interfere with these concentrations, Stockey says. For example, a localized increase in organic carbon in black shales could increase the amount of molybdenum and uranium present in a particular sample. Stockey applied statistical and machine learning methods to analyze geochemical data from a much larger sample of black shale to unravel the signal in the rocks. He then used oceanographic models to estimate oxygen levels in Earth's atmosphere and oceans.

“We found that many of the trace metal changes that scientists have observed over the last 15 to 20 years are being driven by changes in organic carbon in the black shales,” Stockey said. It wasn't until the Devonian period, 140 million years after the Cambrian explosion, that we saw trace metals increase at rates that indicate ocean-wide oxygenation.

Trilobite fossils from the Cambrian Rock Formation in Jasper National Park, Alberta, Canada. | Erik Sperling

Consortium for Geochemical Data

The black shale data was compiled as part of the Sedimentary Geochemistry and Paleoenvironment Project, a research consortium that Sperling launched in 2015 to compile geochemical data into a standardized database for large-scale analysis. While the consortium's approach to collecting, harmonizing and analyzing data is common in other fields, Sperling was inspired by the way biomedical research consortia study disease – the first of its kind in geology.

“This is a completely different approach than we've used in the field before,” Sperling says. “Each group, including us, goes out there and figures out what's going on, but then we all have to come together and analyze it.”

The analytical toolkit that Stockey developed for this study could help researchers understand not only ancient oxygen levels, but also temperature, food supply and other potential drivers of early evolution. Consortium members are also collecting new data to fill in periods of geological time where samples are scarce, and conducting analyses that extend to older and more recent time periods.

Stockey says that to harness the power of these more advanced data science approaches, especially when it comes to geological data, we all need to speak the same language: This community-driven data science approach has allowed us to be much more confident about how we reconstruct the spatial and temporal evolution of the Earth.

For more information

Sperling is a member of Stanford BioX and a senior research scientist at the Stanford Woods Institute for the Environment.

Stanford co-authors on the study include postdoctoral researcher Christina R. Waltz and doctoral student Samantha R. Ritzer in the Department of Earth and Planetary Sciences at Stanford's Door School of Sustainability. Dr. Thomas H. Borg (2010) and Dr. Malcolm S. W. Hodgkiss (2010) worked on the study as doctoral students in the Sperlings Laboratory in the Department of Geological Sciences (now the Department of Earth and Planetary Sciences). Dr. Borg is now at Columbia University and Dr. Hodgkiss is now at UNESCO.

Additional co-authors are from Georgia Institute of Technology, Trinity College Dublin, Durham University, University of California, Santa Barbara, Australian National University, University of Southern Denmark, China National Petroleum Corporation (PetroChina), Chengdu University of Technology, Woods Hole Oceanographic Institution, Carleton University, Mississippi State University, University of Copenhagen, Harvard University, University of São Paulo, Geological Survey of Canada, University of Wisconsin-Milwaukee, CGG, Pomona College, Yale University, Virginia Tech, George Mason University, Kansas State University, University of Toulouse, McGill University, Lund University, Johns Hopkins University, University of Texas at Austin, Permian Basin, University of Calgary, Norwegian Geological Survey, University of Cambridge, Geological Survey of the Northern Territory, and Museum für Naturkunde Karlsruhe. Fortescue Metals Group Ltd, University of Portsmouth, GFZ German Research Centre for Geosciences, University of Texas at Austin, Australian Water Environment Regulatory Agency, University of Wisconsin-Madison, University of Leeds, Western Carolina University, Dartmouth College, Universidade Federal de Minas Gerais, University of Edinburgh and University of Texas at Dallas. The research was funded by the National Science Foundation and the American Chemical Society.

Sources 1/ https://Google.com/ 2/ https://news.stanford.edu/stories/2024/07/revisiting-the-cambrian-explosion-s-spark The mention sources can contact us to remove/changing this article

What Are The Main Benefits Of Comparing Car Insurance Quotes Online

LOS ANGELES, CA / ACCESSWIRE / June 24, 2020, / Compare-autoinsurance.Org has launched a new blog post that presents the main benefits of comparing multiple car insurance quotes. For more info and free online quotes, please visit https://compare-autoinsurance.Org/the-advantages-of-comparing-prices-with-car-insurance-quotes-online/ The modern society has numerous technological advantages. One important advantage is the speed at which information is sent and received. With the help of the internet, the shopping habits of many persons have drastically changed. The car insurance industry hasn't remained untouched by these changes. On the internet, drivers can compare insurance prices and find out which sellers have the best offers. View photos The advantages of comparing online car insurance quotes are the following: Online quotes can be obtained from anywhere and at any time. Unlike physical insurance agencies, websites don't have a specific schedule and they are available at any time. Drivers that have busy working schedules, can compare quotes from anywhere and at any time, even at midnight. Multiple choices. Almost all insurance providers, no matter if they are well-known brands or just local insurers, have an online presence. Online quotes will allow policyholders the chance to discover multiple insurance companies and check their prices. Drivers are no longer required to get quotes from just a few known insurance companies. Also, local and regional insurers can provide lower insurance rates for the same services. Accurate insurance estimates. Online quotes can only be accurate if the customers provide accurate and real info about their car models and driving history. Lying about past driving incidents can make the price estimates to be lower, but when dealing with an insurance company lying to them is useless. Usually, insurance companies will do research about a potential customer before granting him coverage. Online quotes can be sorted easily. Although drivers are recommended to not choose a policy just based on its price, drivers can easily sort quotes by insurance price. Using brokerage websites will allow drivers to get quotes from multiple insurers, thus making the comparison faster and easier. For additional info, money-saving tips, and free car insurance quotes, visit https://compare-autoinsurance.Org/ Compare-autoinsurance.Org is an online provider of life, home, health, and auto insurance quotes. This website is unique because it does not simply stick to one kind of insurance provider, but brings the clients the best deals from many different online insurance carriers. In this way, clients have access to offers from multiple carriers all in one place: this website. On this site, customers have access to quotes for insurance plans from various agencies, such as local or nationwide agencies, brand names insurance companies, etc. "Online quotes can easily help drivers obtain better car insurance deals. All they have to do is to complete an online form with accurate and real info, then compare prices", said Russell Rabichev, Marketing Director of Internet Marketing Company. CONTACT: Company Name: Internet Marketing CompanyPerson for contact Name: Gurgu CPhone Number: (818) 359-3898Email: [email protected]: https://compare-autoinsurance.Org/ SOURCE: Compare-autoinsurance.Org View source version on accesswire.Com:https://www.Accesswire.Com/595055/What-Are-The-Main-Benefits-Of-Comparing-Car-Insurance-Quotes-Online View photos