New, tighter timeline confirms ancient volcanism aligned with dinosaurs' extinction

December 18, 2014
A definitive geological timeline from Princeton University researchers shows that a series of massive eruptions 66 million years ago in a primeval volcanic range in western India known as the Deccan Traps played a role in the extinction event that claimed Earth's non-avian dinosaurs, and challenges the dominant theory that a meteorite impact was the sole cause of the extinction. Pictured above are the Deccan Traps near Mahabaleshwar, India. Credit: Gerta Keller, Department of Geosciences

A definitive geological timeline shows that a series of massive volcanic explosions 66 million years ago spewed enormous amounts of climate-altering gases into the atmosphere immediately before and during the extinction event that claimed Earth's non-avian dinosaurs, according to new research from Princeton University.

A primeval volcanic range in western India known as the Deccan Traps, which were once three times larger than France, began its main phase of eruptions roughly 250,000 years before the Cretaceous-Paleogene, or K-Pg, , the researchers report in the journal Science. For the next 750,000 years, the volcanoes unleashed more than 1.1 million cubic kilometers (264,000 cubic miles) of lava. The main phase of eruptions comprised about 80-90 percent of the total volume of the Deccan Traps' lava flow and followed a substantially weaker first phase that began about 1 million years earlier.

The results support the idea that the Deccan Traps played a role in the K-Pg extinction, and challenge the dominant theory that a meteorite impact near present-day Chicxulub, Mexico, was the sole cause of the extinction. The researchers suggest that the Deccan Traps eruptions and the Chicxulub impact need to be considered together when studying and modeling the K-Pg extinction event.

The Deccan Traps' part in the K-Pg extinction is consistent with the rest of Earth history, explained lead author Blair Schoene, a Princeton assistant professor of geosciences who specializes in geochronology. Four of the five largest extinction events in the last 500 million years coincided with large volcanic eruptions similar to the Deccan Traps. The K-Pg extinction is the only one that coincides with an asteroid impact, he said.

"The precedent is there in Earth history that significant climate change and biotic turnover can result from , and therefore the effect of the Deccan Traps on late-Cretaceous ecosystems should be considered," Schoene said.

The researchers used a precise rock-dating technique to narrow significantly the timeline for the start of the main eruption, which until now was only known to have occurred within 1 million years of the K-Pg extinction, Schoene said. The Princeton group will return to India in January to collect more samples with the purpose of further constraining eruption rates during the 750,000-year volcanic episode.

New, tighter timeline confirms ancient volcanism aligned with dinosaurs' extinction
The researchers suggest that the Deccan Traps eruptions and the meteorite impact near present-day Chicxulub, Mexico, need to be considered together when studying and modeling the Cretaceous-Paleogene extinction event. The main eruption phases for the Deccan Traps (in brown), which were once three times larger than France, began roughly 250,000 years before the extinction event, the researchers found. For the next 750,000 years, the volcanoes unleashed more than 1.1 million cubic kilometers (264,000 cubic miles) of lava, which comprised about 80-90 percent of the total volume of the Deccan Traps' lava flow. The amount of carbon dioxide and sulfur dioxide the volcanoes poured out would have caused severe ecological fallout. Credit: Matilda Luk

Schoene and his co-authors gauged the age of petrified lava flows known as basalt by comparing the existing ratio of uranium to lead given the known rate at which uranium decays over time. The uranium and lead were found in tiny grains—less than a half-millimeter in size—of the mineral zircon. Zircon is widely considered Earth's best "time capsule" because it contains a lot of uranium and no lead when it crystallizes, but it is scarce in basalts that cooled quickly. The researchers took the unusual approach of looking for zircon in volcanic ash that had been trapped between lava flows, as well as within thick basalt flows where lava would have cooled more slowly.

The zircon dated from these layers showed that 80-90 percent of the Deccan Traps eruptions occurred in less than a million years, and began very shortly—in geological terms—before the K-Pg extinction. To produce useful models for events such as the K-Pg extinction, scientists want to know the sequence of events to within tens of thousands of years or better, not millions, Schoene said. Margins of millions of years are akin to "a history book with events that have no dates and are not written in chronological order," he said.

"We need to know which events happened first and how long before other events, such as when did the Deccan eruptions happen in relation to the K-Pg extinction," Schoene said. "We're now able to place a higher resolution timeframe on these eruptions and are one step closer to finding out what the individual effects of the Deccan Traps eruptions were relative to the Chicxulub meteorite."

Vincent Courtillot, a geophysicist and professor at Paris University Diderot, said that the paper is important and "provides a significant improvement on the absolute dating of the Deccan Traps." Courtillot, who is familiar with the Princeton work but had no role in it, led a team that reported in the Journal of Geophysical Research in 2009 that Deccan volcanism occurred in three phases, the second and largest of which coincides with the K-Pg mass extinction. Numerous other papers from his research groups are considered essential to the development of the Deccan Traps hypothesis. (The Princeton researchers also plan to test the three-phases hypothesis, Schoene said. Their data already suggests that the second and third phase might be a single period of eruptions bridged by smaller, "pulse" eruptions, he said.)

The latest work builds on the long-time work by co-author Gerta Keller, a Princeton professor of geosciences, to establish the Deccan Traps as a main cause of the K-Pg extinction. Virginia Tech geologist Dewey McLean first championed the theory 30 years ago and Keller has since become a prominent voice among a large group of scientists who advocate the idea. In 2011, Keller published two papers that together proposed a one-two punch of Deccan volcanism and meteorite strikes that ended life for more than half of Earth's plants and animals.

The researchers took an unusual approach to find the mineral needed to construct the timeline for the start of the main Deccan Traps eruption. They compared the existing ratio of uranium to lead in petrified lava flows known as basalts given the known rate at which uranium decays over time. To have enough uranium, however, the researchers needed the mineral zircon, which is scarce in basalts that cooled quickly. Turning to new sources, the researchers found zircon in soil deposits known as red boles (right) that formed in between eruptions and contain volcanic ash (left) that had been trapped between lava flows. They also located zircon within thick basalt flows where lava would have cooled more slowly. Credit: Blair Schoene, Department of Geosciences

Existing models of the environmental effects of the Deccan eruptions used timelines two to three times longer than what the researchers found, which underestimated the eruptions' ecological fallout, Keller explained. The amount of carbon dioxide and sulfur dioxide the volcanoes poured out would have produced, respectively, a long-term warming and short-term cooling of the oceans and land, and resulted in highly acidic bodies of water, she said.

Because these gases dissipate somewhat quickly, however, a timeline of millions of years understates the volcanoes' environmental repercussions, while a timeframe of hundreds of thousands of years—particularly if the eruptions never truly stopped—provides a stronger correlation. The new work confirms past work by placing the largest Deccan eruptions nearer the K-Pg extinction, but shows a much shorter time frame of just 250,000 years, Keller said.

"These results have significantly strengthened the case for volcanism as the primary cause for the mass extinction, as well as for the observed rapid climate changes and ocean acidification," Keller said.

"The Deccan Traps mass hypothesis has already enjoyed wide acceptance based on our earlier work and a number of studies have independently confirmed the global effects of Deccan volcanism just prior to the ," she said. "The current results will go a long way to strengthen the earlier results as well as further challenge the dominance of the Chicxulub hypothesis."

Explore further: Experts reaffirm asteroid impact caused mass extinction 65 million years ago (w/ Video)

More information: The paper, "U-Pb geochronology of the Deccan Traps and relation to the end-Cretaceous mass extinction," was published Dec. 11 in Science: www.sciencemag.org/content/early/2014/12/10/science.aaa0118

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12 comments

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Jim4321
4 / 5 (1) Dec 18, 2014
How do you calibrate to a time resolution of one part in a thousand (or in ten thousand) sixty six million years ago? To obtain the estimate absolutely, i.e.without some calibration reference, you would need to understand the chemistry of zircon and its leach rates very very precisely. At that level you might even need to correct for cosmic rays as wsell as the geochemistry. I am truly impressed if this kind of time resolution can be obtained. But without calibration how can we be sure?
DonGateley
3 / 5 (1) Dec 19, 2014
Has anything changed enough in 66 million years to say that such an event as the Deccan Traps can't occur now?
Maggnus
5 / 5 (4) Dec 19, 2014
Has anything changed enough in 66 million years to say that such an event as the Deccan Traps can't occur now?


No actually, and a small version of the traps occurred in Iceland around 1785 AD. It's called a fissure eruption. Of course, the one in the 1700s only lasted a few months, whereas the Deccan traps lasted several millennium. Its interesting to note, however, that even that relatively modest eruption killed about a 1/4 of the Icelandic population and affected temperatures across the planet, leading to some 6 million deaths.
Anda
1.5 / 5 (4) Dec 19, 2014
"News" is the funny thing. Lately there are lots of sensationalist titles and introductory sentences.
In this case for instance the study may be recent, but the conclusions aren't.
We already know the existence of these traps and we also already suspect the meteor wasn't the only cause of the extinction.

Sensationalism? Lack of knowledge? Of interest?
There's something wrong. People without a background on a subject are misleaded by this writing style. It wasn't this way before.
Selena
Dec 19, 2014
This comment has been removed by a moderator.
Maggnus
5 / 5 (6) Dec 19, 2014
tighter timeline confirms ancient volcanism aligned with dinosaurs' extinction
If the meteorite hypothesis is also valid, it would mean, both events (meteorite impact and period of volcanism) were aligned too. I believe, we're currently experiencing this coincidence too, just in rather mild form. The solar system is cloud at the galactic plane (probably the shadow of dark Great rift being more specific) - the increased density of scalar waves accelerates the nuclear reactions in Earth crust, soil and marine water. The methane and carbon dioxide escapes into atmosphere and creates an illusion of AGW for us. It also enforces the geovolcanism and frequency of impactors deflected from their stable paths with gravitation of dark matter. The temporal coincidence of Deccan Traps formation with Yucatan asteroid cannot serve as an evidence - but it may serve as an indicia of this model.

Quack! Quack quack quack QUACK! Another Zephyr sock puppet.
tear88
5 / 5 (4) Dec 20, 2014
Maggnus: :-)

I failed to note the name, so it wasn't until I reached "entering dark matter cloud" that I exclaimed, WTF? I didn't bother to read further.

My only comment about the article is, homo sapiens is standing in for massive vulcanism this time.
Anonym
4 / 5 (1) Dec 21, 2014
Wouldn't the shock wave from the large meteor impact trigger intense volcanism on the opposite side of the globe? Is it novel, their claim that the extinction took 250,000 years or more to accomplish?
Maggnus
5 / 5 (2) Dec 21, 2014
Wouldn't the shock wave from the large meteor impact trigger intense volcanism on the opposite side of the globe? Is it novel, their claim that the extinction took 250,000 years or more to accomplish?


That can happen, but it would take a very large object to do it. There is evidence it has happened on other bodies in the solar system, but I don't think this impact was large enough.

Furthermore, in this specific case, there is strong evidence to suggest the Deccan Traps had been active for eons before the asteroid strike.
Captain Stumpy
5 / 5 (1) Dec 21, 2014
How do you calibrate to a time resolution of ...
@Jim4321
The study is paywalled for you? I will share what i can with regard to the paragraphs of data about calibration
These data also calibrate the timing of magnetic polarity Chron 29r, which serves as a basis for global correlation of KPB sections. The C29r/C29n reversal was previously identified within the lower Mahabaleshwar Fm (5), from which we collected samples RBP, RBE, and RBF. We use the 206Pb/238U date of sample RBE of 65.552 ± 0.026/0.049/0.086 Ma (2σ uncertainties here given as internal only/with tracer calibration/with 238U decay constant) as our best estimate for the age of C29r/C29n reversal because it was sampled from between two basalts with transitional polarity (Fig. 1) (5). The basal age of C29r is constrained by sample DEC13-30, which was collected from a basaltic segregation vein within the Jawhar Fm near the base of the main Deccan phase
[ctd next post]
Captain Stumpy
5 / 5 (1) Dec 21, 2014
[ctd]
near the base of the main Deccan phase and yielded a 206Pb/238U date of 66.288 ± 0.027/0.047/0.085 Ma. From the same outcrop, Chenet et al. (9) reported transitional magnetic polarity just tens of meters beneath lavas containing reverse polarity (C29r); from this transitional horizon they reported a K-Ar date of 67.4 ± 2.0 Ma. Though their date was interpreted to represent the C30r/C30n or C31n/C30r transition, with a long hiatus in eruptions represented in that section (9), our U-Pb date from DEC13-30 is not consistent with a hiatus of that magnitude. A simpler interpretation is that the transitional polarity basalts represent the C30n/C29r transition. Thus the age difference between DEC13-30 and RBE of 736 ± 37 kyr is also the length of C29r.
[cont next post]
Captain Stumpy
5 / 5 (1) Dec 21, 2014
[ctnd]
An independent estimate for the length of C29r from cyclostratigraphic analysis of marine ODP cores and the Zumaia section, Spain, yields durations of 713-725 kyr (22), in good agreement with our calibration based on U-Pb geochronology.


There is a LOT more data contained in the next two paragraphs, Jim, but i think you have an idea of how they are calibrating the data, using the constraints placed upon each time period by the data of other samples from various regions

Is that clear enough?
You can request the rest of the study from ScienceMag, or perhaps part of it by directing an inquiry of the listed author who's linked as the contact: Blair Schoene from Princeton

you should be able to address an e-mail to Princeton or research Princeton to get the info... if not, you can contact me at http://saposjoint.net under the profile "Truck Captain Stumpy" and i can give the e-mail address to you from the study

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