Mercury helps to detail Earth's most massive extinction event

Date:
January 27, 2023
Source:
University of Connecticut
Summary:
Scientists are working to understand the cause and how the events
of the LPME unfolded by focusing on mercury from Siberian volcanoes
that ended up in sediments in Australia and South Africa.


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FULL STORY ==========================================================================
The Latest Permian Mass Extinction (LPME) was the largest extinction in
Earth's history to date, killing between 80-90% of life on the planet,
though finding definitive evidence for what caused the dramatic changes
in climate has eluded experts.


==========================================================================
An international team of scientists, including UConn Department of
Earth Sciences researchers Professor and Department Head Tracy Frank and Professor Christopher Fielding, are working to understand the cause and
how the events of the LPME unfolded by focusing on mercury from Siberian volcanoes that ended up in sediments in Australia and South Africa. The research has been published in Nature Communications.

Though the LPME happened over 250 million years ago, there are
similarities to the major climate changes happening today, explains
Frank: "It's relevant to understanding what might happen on earth in
the future. The main cause of climate change is related to a massive
injection of carbon dioxide into the atmosphere around the time of the extinction, which led to rapid warming." In the case of the LPME, it
is widely accepted that the rapid warming associated with the event is
linked to massive volcanism occurring at a huge deposit of lava called
the Siberian Traps Large Igneous Province (STLIP), says Frank, but direct evidence was still lacking.

Volcanos leave helpful clues in the geological record. With the outpouring
of lava, there was also a huge quantity of gases released, such as CO2
and methane, along with particulates and heavy metals that were launched
into the atmosphere and deposited around the globe.

"However, it's hard to directly link something like that to the extinction event," says Frank. "As geologists, we're looking for a signature of some
kind -- a smoking gun -- so that we can absolutely point to the cause."
In this case, the smoking gun the researchers focused on was mercury,
one of the heavy metals associated with volcanic eruptions. The trick
is finding areas where that record still exists.

Frank explains there is a continuous record of the earth's history
contained in sediments in marine environments which acts almost like a
tape recorder because deposits are quickly buried and protected. These sediments yield an abundance of data about the extinction and how it
unfolded in the oceans. On land, it is more difficult to find such well-preserved records from this time period.

To illustrate this, Frank uses Connecticut as an example: the state is
rich with 400-500-million-year-old metamorphic rocks at or near the
surface, with a covering of glacial deposits dating to around 23,000
years ago.

"There's a big gap in the record here. You have to be lucky to preserve terrestrial records and that's why they aren't as well studied, because
there are fewer of them out there," says Frank.

Not all terrains around the world have such massive gaps in the geologic record, and previous studies of the LPME have focused primarily on sites
found in the northern hemisphere. However, the Sydney Basin in Eastern Australia and the Karoo Basin in South Africa are two areas in the
southern hemisphere that happen to have an excellent record of the event,
and are areas Frank and Fielding have studied previously. A colleague
and co-author, Jun Shen from the State Key Laboratory of Geological
Processes and Mineral Resources at the China University of Geosciences,
reached out and connected with Frank, Fielding, and other co-authors
for samples, with hopes to analyze them for mercury isotopes.

Shen was able to analyze the mercury isotopes in the samples and tie
all the data together says Frank.

"It turns out that volcanic emissions of mercury have a very specific
isotopic composition of the mercury that accumulated at the extinction
horizon. Knowing the age of these deposits, we can more definitively tie
the timing of the extinction to this massive eruption in Siberia. What
is different about this paper is we looked not only at mercury, but the isotopic composition of the mercury from samples in the high southern latitudes, both for the first time." This definitive timing is something
that scientists have been working on refining, but as Fielding points out,
the more that we learn, the more complicated it gets.

"As a starting point, geologists have pinpointed the timing of the major extinction event at 251.9 million years with a high degree of precision
from radiogenic isotope dating methods. Researchers know that is when
the major extinction event happened in the marine environment and it
was just assumed that the terrestrial extinction event happened at the
same time." In Frank and Fielding's previous research, they found that
the extinction event on land happened 200-600,000 years earlier, however.

"That suggests that the event itself wasn't just one big whammy that
happened instantaneously. It wasn't just one very bad day on Earth,
so to speak, it took some time to build and this feeds in well into
the new results because it suggests the volcanism was the root cause,"
says Fielding. "That's just the first impact of the biotic crisis that
happened on land, and it happened early.

It took time to be transmitted into the oceans. The event 251.9 million
years ago was the major tipping point in environmental conditions in
the ocean that had deteriorated over some time." Retracing the events
relies on knowledge from many different geologists all specializing
in different methods, from sedimentology, geochemistry, paleontology,
and geochronology, says Frank, "This type of work requires a lot of collaboration. It all started with fieldwork when a group of us went
down to Australia, where we studied the stratigraphic sections that
preserved the time interval in question. The main point is that we now
have a chemical signature in the form of mercury isotope signatures,
that definitively ties the extinction horizon in these terrestrial
sections that provide a record of what was happening on land due to
Siberian Traps volcanism."
* RELATED_TOPICS
o Earth_&_Climate
# Climate # Global_Warming # Geology # Earth_Science
o Fossils_&_Ruins
# Early_Climate # Fossils # Dinosaurs # Origin_of_Life
* RELATED_TERMS
o Gondwana o Shield_volcano o Mercury_poisoning o
Decade_Volcanoes o Plate_tectonics o Mount_Etna o
Timeline_of_environmental_events o Mountain

========================================================================== Story Source: Materials provided by University_of_Connecticut. Original
written by Elaina Hancock. Note: Content may be edited for style and
length.


========================================================================== Journal Reference:
1. Jun Shen, Jiubin Chen, Jianxin Yu, Thomas J. Algeo, Roger
M. H. Smith,
Jennifer Botha, Tracy D. Frank, Christopher R. Fielding, Peter
D. Ward, Tamsin A. Mather. Mercury evidence from southern Pangea
terrestrial sections for end-Permian global volcanic effects. Nature
Communications, 2023; 14 (1) DOI: 10.1038/s41467-022-35272-8 ==========================================================================

Link to news story: https://www.sciencedaily.com/releases/2023/01/230127131139.htm

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