Sometimes one just has to get
lucky. An alpine meadow at Aspen turns out to be a former lake that acted as a
capture trap for an unending series of local fauna in the same manner as the la
Brea
I suspect other portions of the
site can be also excavated at a more leisurely pace once the reservoir is
established. In the event, huge
inventories of specimens have been acquired, to inform us for decades to come.
I have just returned from Drumhiller
and the premier museum in Western Canada which
has gone from a dinosaur dig in the badlands to one of the premier global
collections and now a major center of paleontology. It collects from sites all over western Canada
The collection is a must see and I
was impressed to see so many lined up to pay admission on a Monday morning. More amusing it appears that a local sculptor
in fiber glass has sustained himself by producing a great many local dinosaur
models for just about every business in town.
Pleistocene Treasures, at a Breakneck Pace
Published: July 4, 2011
More than 130,000 years ago in the chilled depths of the Illinoian ice
age, an errant glacier left a hole atop a 9,000-foot-high ridge near what would
become the town of Aspen in the central Colorado Rockies. The depression filled
with snowmelt, and for tens of thousands of years, the little lake attracted
the giants of the Pleistocene — mammoths, mastodons, ground sloths half again
the size of grizzly bears, supersize bison, camels and horses — that came to
drink, and in many cases to die, in the high alpine mud.
The second time scale was more like a runner’s sprint. Scientists had
only 70 days — a number framed by mountain winter weather and lawyerly fine
print — to search the old lake bed sediments for remnants of these ancient
animals.
That was from Oct. 14, when workers on a reservoir dam turned over the
first fossil bones (of a young female mammoth, promptly nicknamed Snowy) to
last weekend, when work on the reservoir resumed. A tight contract schedule
dictates that the reservoir, which will supply the condos and ski lodges of
Snowmass, must be completed by late this year. The result was a frantic race to
find and catalog everything possible before the site was entombed once more by
water.
The breakneck pace of the fossil dig was matched only by what
scientists said was the extraordinary richness of the site, one of the best
windows into the thundering megafauna of its time. “The speed of this thing is
so unlike normal science — from discovery to completion of one of the biggest
digs ever in less than nine months,” said Kirk R. Johnson, the chief curator of
the Denver Museum of Nature and Science, who oversaw the project. (He is no
relation to this reporter.)
“Typically, you write a grant proposal and wait nine months to hear
anything,” Dr. Johnson said. “We couldn’t wait — in a single day, we were
finding a couple hundred bones.”
The ancient Snowmass clock was measured in the untold lives of the
creatures that roamed and roared in a place and period poorly recorded in the
scientific record: The high reaches of Rocky Mountains during the Sangamonian
interglacial, a time of very warm weather around the globe, 75,000 to 125,000
years ago.
Other well-known ice age fossil sites, by contrast, like the La Brea
Tar Pits in California and Hot Springs, S.D., have been dated to between 10,000
and 40,000 before present, and no well-preserved site has ever been found,
scientists said, at this altitude in North America.
Here at Snowmastodon, as the site is called, the human clock ran partly
on adrenaline, with 50 or more shovel-wielding scientists, volunteers and
interns from the Denver
Museum
Something very big — a mammoth tusk taller than LeBron James, a partial
mastodon skull half the size of a Smart Car — was turning up every few days. By
the end, more than 4,500 fossil specimens from 20 different animals were hauled
out.
“Bone up!” Dr. Johnson shouted on recent, brilliantly sunny day, as a
cheer rose across the pit. “Arm bone of a sloth,” Dr. Johnson said casually
from a practiced distance, when the huge humerus was held aloft by its finder.
Preliminary estimates say the ancient ridge-top lake — unusual in
having no stream inlet to bring in sediment — might have persisted for as long
as 100,000 years before windblown dust filled it in to become a typical-looking
alpine meadow, a state it had reached 50,000 years or more before humans came
to the Americas
The resulting fossil bed thus has a long climate record in its pollens,
buried plants and windborne particles, as well as a long yardstick of the
animals and what might be deduced about their lives. The sediment layers
suggest periods when the lakeside landscape was tundra — too cold for trees —
and others when great forests hugged the shore.
“I think at the end of the day that’s what’s going to be so valuable —
you’ve got this crystal-clear glimpse into the Rockies before humans show up,”
said Ian Miller, curator of paleobotany at the Denver museum. “We’re sitting
here at almost 9,000 feet, and climate is driving ecosystems up and down. It’s
a window, and you just watch it go by.”
A businessman from Wisconsin
The growing water needs of Snowmass Village, founded in the 1960s,
eventually led engineers to look for a reservoir site, which led to the
backhoes, and the first discoveries last fall, and which will lead, in a grand
circling back of history, to an eventual restoration of meadow’s use as a watering
hole. The accelerated pace was partly because the Snowmass Water and Sanitation
Department District, under its contract with the Ziegler family, which still
owns the land around the lake, faced substantial financial penalties if the
work wasn’t completed on time. The reservoir must be up and running by next
spring under the contract, but because winter will close down the work late
this year, just as it did on the dig, that means finishing up before snow
flies.
The dig, partly supported by a grant from the National Geographic
Society, will be featured in a National Geographic-Nova special on PBS next
year.
“We cross-country skied over where those creatures once roamed, and we
never had any idea,” said Peter Ziegler, 62, who spent two days at the dig in
June, laboring with a shovel.
There are still many unanswered questions about what happened here —
most pointed is, when did the animals actually die?
Because the site is too old for radiocarbon dating, which is only
useful to about 50,000 years before present, other more complicated methods,
all of which take longer to work out, will have to be used. Ancient pollen, for
example, was collected from the mud to compare against other climate indicators.
Core samples will be examined for markers like volcanic dust, which might be
dated using radiometric dating techniques based on argon 40-39 or uranium-lead
geochronology.
Secondly, the animals did not march to their deaths in a steady
procession over the centuries. There are sediment layers with few bones,
followed by layers with many bones — indicating, Dr. Johnson said, that the
lake may have multiple stories to tell. The remains of young animals found in
the pit could suggest, for example, that through at least through part of its
history the lake was a trap, with slippery slopes or lethal leg-sucking goo,
like the La Brea Tar Pits.
The third great question, connected to everything else, is how the
great shifts of climate recorded by the mud affected the lives and habits of
the creatures that roamed here.
Was the climate warm enough in the interglacial period, which peaked in
temperature around 110,000 years ago, that elephant-family relatives and other
animals like camels and sloths could live year round at high altitude, or were
there migratory patterns — highlands in the summers, lowlands in winter — that
might emerge? For instance, will the growth rings of mastodon or mammoth tusks
found here differ from those of cousins found at low altitude sites, hinting at
permanent mountain residence?
“That’s the kind of question we couldn’t even ask before this site was
discovered,” Dr. Johnson said.
Some researchers are hoping the finds will yield DNA that might give a
glimpse into the genes of ice age mammals. Genetic diversity, or uniformity,
can suggest how big a population was at the time of an individual’s death.
“The interglacial period wasn’t a great time for stuff to be
preserved,” said Beth Shapiro, an associate professor of biology at Pennsylvania State University
“Scale” is the word that researchers and volunteers used over and over,
from the timeline to the volume of specimens to the crush of pressure to the
trove of data that will fill research agendas for years to come.
Chris Faison, a schoolteacher from Aspen
After the news broke last fall about the archaeological treasure trove,
his school built a mastodon model to scale, 12 feet tall at the shoulder — and
Mr. Faison said the first and second graders he teaches shared his awe.
“I never thought I’d see this kind of stuff,” he said, pushing his
shovel into the mud.
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