[meteorite-list] Collapse Of Simple Life Forms Linked To Mass Extinctions 200 Million Years Ago

From: Ron Baalke <baalke_at_meteoritecentral.com>
Date: Thu Apr 22 09:46:23 2004
Message-ID: <200105111642.JAA09800_at_zagami.jpl.nasa.gov>

http://www.washington.edu/newsroom/news/2001archive/05-01archive/k051001.html


FOR IMMEDIATE RELEASE

Vince Stricherz
University Of Washington
206-543-2580
vinces_at_u.washington.edu
May 10, 2001

Collapse of simple life forms linked to mass extinction 200 million years ago

A mass extinction about 200 million years ago, which destroyed at least half of the
species on Earth, happened very quickly and is demonstrated in the fossil record
by the collapse of one-celled organisms called protists, according to new
research led by a University of Washington paleontologist.

"Something suddenly killed off more than 50 percent of all species on Earth,
and that led to the age of dinosaurs," said Peter Ward, a UW Earth and space
sciences professor.

Evidence indicates the massive die-off was linked with an abrupt drop in
productivity, the rate at which inorganic carbon is turned into organic
carbon through processes such as photosynthesis. The waning productivity
coincided with a sharp decline in radiolaria (included among protists),
which was the focus of the new research. One example of productivity, Ward
explained, occurs in the spring when fertilizer washes into waterways and
triggers large algae blooms. The processes at work in that scenario were
reversed 200 million years ago, he said.

There is no definitive evidence yet on what caused the demise of so many
species, Ward said. However, the suddenness of the event is similar to two
better-known mass extinctions - one 250 million years ago at the end of the
Permian period that killed some 90 percent of all species, the other 65
million years ago at the end of the Cretaceous period that sent the
dinosaurs into oblivion.

The extinction 200 million years ago, at the boundary between the Triassic
and Jurassic periods, killed the last of the mammal-like reptiles that once
roamed the Earth and left mainly dinosaurs, Ward said. That extinction
happened in less than 10,000 years, in the blink of an eye, geologically
speaking.

Ward is the lead author on a paper detailing the evidence, published in the
May 11 edition of the journal Science. Others participating in the research
are James Haggart and Howard Tipper of the Geological Survey of Canada in
Vancouver, British Columbia; Elizabeth Carter, a researcher at Oregon's
Portland State University; David Wilbur, a UW oceanography research
scientist; and Tom Evans, a UW junior in chemistry and Earth and space
sciences.

The evidence from the extinction was gathered at two sites in the Queen
Charlotte Islands, off Canada's British Columbia coast.

"These sites are among the most remote places in the world," Ward said.
"There are no roads anywhere close by. The forests are virgin old growth,
and the wave action is such that you can't get there by boat."

Samples from a spot called Kennecott Point, in the northern Queen
Charlottes, and from Kunga Island, about 100 miles to the southeast, showed
a sharp decline in the presence of organic carbon, even at places where
levels of inorganic carbon rose. The organic carbon decline correlated with
the decline of radiolarians, one-celled organisms that serve as a food
source for a number of marine species.

"These provide the best record of how nasty the extinction was at this
boundary," Ward said.

The mass extinction 200 million years ago occurred just before the breakup
of Pangea, which contained all the land on Earth in one supercontinent. At
the time, the Queen Charlotte Islands - which now lie between 52 and 54
degrees north latitude - were probably on the equator or in the southern
hemisphere, Ward said.

"These are tropical fossils. There are many kinds of fossils in these
rocks," he said.

And they tell a story of a calamity that came on with stunning swiftness.

"This is the first time ever that we can see how sudden this event was," he
said. "It was very quick, not a long protracted episode."

Ward now has done research on the last three of the Earth's mass extinctions
(scientists know of five) and has found that each happened quite quickly.

Bolstered by a recent astrobiology grant from the National Aeronautics and
Space Administration, he plans to lead researchers back to the Queen
Charlottes this summer to look for more clues in the Triassic-Jurassic
extinction, including potential causes.

###

For more information, contact Ward at (206) 543-2962 or
argo_at_u.washington.edu
Received on Fri 11 May 2001 12:42:15 PM PDT