New dating of a major ancient warming shows warming started before major eruptions | High-precision U-Pb geochronology for the Miocene Climate Optimum and a novel approach for calibrating age models in deep-sea sediment cores

From the news article:

>One object of study is a warming event known as the Miocene Climate Optimum (MCO) from about 17 to 15 million years ago. It coincided with floods of basalt lava that covered a large area of the Northwestern US, creating what are called the “Columbia River Basalts.” This timing suggests that volcanic CO2 was the cause of the warming.
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>Those eruptions were the most recent example of a “Large Igneous Province,” a phenomenon that has repeatedly triggered climate upheavals and mass extinctions throughout Earth’s past. The Miocene version was relatively benign; it saw CO2 levels and global temperatures rise, causing ecosystem changes and significant melting of Antarctic ice, but didn’t trigger a mass extinction.
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>A paper just published in Geology, led by Jennifer Kasbohm of the Carnegie Science’s Earth and Planets Laboratory, upends the idea that the eruptions triggered the warming while still blaming them for the peak climate warmth.
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>The study is the result of the world’s first successful application of high-precision radiometric dating on climate records obtained by drilling into ocean sediments, opening the door to improved measurements of past climate changes. As a bonus, it confirms the validity of mathematical models of our orbits around the Solar System over deep time.
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>The significance of this first successful application of high-precision radiometric dating to marine sediments in drill cores goes far beyond the Miocene Climate Optimum. It paves the way for an improved understanding of environmental changes through hundreds of millions of years of geological climate records.
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>“This is really outstanding,” said Westerhold about the paper. “I think when people see this potential, they will say, ‘Oh! We should try this also.’”
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>Westerhold’s specialty is using orbital wobbles calculated by astronomers to date sediments: “They look a little bit like a bar code, and this bar code can be reproduced by astronomers, and if you fit the bar codes, you know the time,” explained Westerhold.
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>Kasbohm and colleagues compared their results with sediments drilled from two sites in the Pacific Ocean that also recorded the MCO and had been dated using those orbital “bar codes,” whereas Kasbohm’s Caribbean core had not. The ages calculated for the Pacific cores using orbital wobbles were close to Kasbohm’s radiometric ages on her Caribbean core.

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Journal link:

[High-precision U-Pb geochronology for the Miocene Climate Optimum and a novel approach for calibrating age models in deep-sea sediment cores](https://pubs.geoscienceworld.org/gsa/geology/article-abstract/doi/10.1130/G52255.1/645502/High-precision-U-Pb-geochronology-for-the-Miocene)

Abstract:

>Scientific ocean drilling cores recovered years ago (legacy cores), especially as recovered by rotary drilling, commonly show incomplete recovery and core disturbance. We present a novel method to date such cores by presenting the first high-precision U-Pb zircon ages targeting the duration of the Miocene Climate Optimum (MCO; ca. 17−14 Ma) from volcanic ashes at Ocean Drilling Program Site 1000 (on the Nicaragua Rise in the Caribbean Sea). We place these ages within a newly developed framework to address incomplete core recovery and use them to calibrate a high-resolution bulk carbonate δ13C and δ18O record. Our Site 1000 ages show that volcanism of the Columbia River Basalt Group (CRBG) large igneous province was coincident with the interval of greatest sustained MCO warmth at this site. However, if the CRBG were the primary driver of the MCO, our chronology may allow for outgassing preceding volcanism as a major source of CO2. We thus document a promising new way to obtain highly resolved, accurate, and precise numerical age models for legacy deep-sea sediment cores that does not depend on correlation to other records.