cover 2006

Chicxulub, an enormous buried
crater on Mexico’s Yucatan
Peninsula. For several years, the
meteorite theory of extinction was
unchallenged.
About two years ago,
Abramovich’s Ph.D. supervisor at
Princeton University, Prof. Gerta
Keller, rocked this theory. Drilling
in the Mexican crater, Keller’s group
dated the impact to the last 300,000
years of the Cretaceous period,
meaning toward but not at the K-T
boundary.
“This means that the meteor
couldn’t have been the only killing
mechanism,” explains Abramovich.
“It may have been one trigger, but
there were most likely other largescale
events of disastrous
proportions, like severe greenhouse
warming, that took place a few
hundred thousand years before the
K-T extinction.”
Apparently, the dinosaurs were
in trouble long before the K-T
boundary. Using planktic
foraminifera, Abramovich points
out several disasters she believes
contributed to their downfall. By
analyzing the skeletons of the
microfossils, she gleans information
about the oceans’ temperature
millions of years ago. This way, she
has identified a worldwide heating
trend that preceded the K-T
boundary by some 450,000 years.
This warming, holds Abramovich,
corresponds with intensive volcanic
activity in India. At the Deccan traps,
in western India, volcanoes released
huge quantities of lava, creating
greenhouse gases and ultimately
leading to extreme warming on a
global scale.
Deciding to investigate this idea
in different locations around the
world, Abramovich and her team
have been focusing on the last
million years at high resolution.
They examined samples from every
10cm of earth, which corresponds
to 10,000-year periods. Counting the
number of species of planktic
foraminifera, they found fewer and
dwarfed versions of different species
during the warming periods. “This
is definitely due to warming – it
occurred at the same time. The
animals entered a survival mode,
which enabled them to live,” says
Abramovich, who is now using
isotope analysis to further probe the
microfossils.
The Negev location of BGU has
been a boon to Abramovich’s
research. She explains that every
major geological period has a ”type
locality.“ Paleontologists work by
cutting into the earth and examining
layers of rock, each of which
represents a specific period. Wide
layers are desirable, as they grant
researchers detailed descriptions of
the period in question. Tunisia
provides the best type locality for
the K-T period worldwide – nine
meters representing the last 300,000
years of the Cretaceous era, the
Maastrichtian period. The Negev
runs a close second, with its eight
meter-deep layer for the same epoch.
Examining samples from this nextto-ideal
locality, Abramovich and
student, Shlomit Yovel, compare
results to those from around the
world.
Today, after two decades of
scientific battle over the extinction
of the dinosaurs, there are still no
obvious victors. While scientists
have engaged in huge international
efforts and gathered vast data bases
of geo-biological-paleontological
evidence, the answer is still not clear.
The world of the K-T mass
extinctions is so distant in time, so
immense and complex, that the
cause of the extinctions remains
shrouded in mystery. For now,
armed with her revealing planktic
foraminifera, Abramovich remains
firmly devoted to uncovering the
truth.
BGU NOW 17