New volume documents the science at the legendary snowmastodon fossil site in Colorado

Four years ago, a bulldozer operator turned over some bones during construction at Ziegler Reservoir near Snowmass Village, Colorado. Scientists from the Denver Museum of Nature & Science were called to the scene and confirmed the bones were those of a juvenile Columbian mammoth, setting off a frenzy of excavation, scientific analysis, and international media attention. This dramatic and unexpected discovery culminates this month with the publication of the Snowmastodon Project Science Volume in the international journal Quaternary Research.

Fourteen papers by 47 authors from the United States and abroad collectively represent “a new benchmark for understanding climate change in the American West,” said paleontologist Dr. Ian Miller, Snowmastodon Project co-leader and chair of the Museum’s Earth Sciences Department.

Project co-leader and former DMNS chief curator, Dr. Kirk Johnson, and several scientists from the U.S. Geological Survey and academic institutions around the world contributed articles to the journal.

“Nothing beats pulling fossils out of the ground,” said project scientist Dr. Jeff Pigati of the U.S. Geological Survey, “but the site also lets us see what the Colorado Rockies were like during a period of time that we simply couldn’t reach before the discovery.”

The Snowmastodon site was an ancient lake that filled with sediment between 140,000 and 55,000 years ago preserving a series of Ice Age fossil ecosystems. Particularly fortuitous is the high-elevation locale, providing first-time documentation of alpine ecosystems during the last interglacial period between about 130,000 and 110,000 years ago. Because scientists were able to collect and study such a wide range of fauna and flora–from tiny specks of pollen to the bones of giant mastodons–the site emerged as a trove of information that Miller said will inspire future research for years to come.

“This project was unprecedented in its size, speed, and depth of collaboration. The science volume now moves beyond the pure excitement of the discovery to the presentation of its hard science and its implications for understanding the biological and climate history of the Rocky Mountain region,” said Johnson, now the Sant Director of the Smithsonian’s National Museum of Natural History.

Papers in the special edition focus on impacts of climate change, then and now. The site’s ecosystems–plants, insects, and animals combined–varied dramatically in response to climate change.

“In other words, turn the climate dial a little and the ecosystems change considerably. We were also surprised to find that certain periods in the record that seem to be cool elsewhere in North America were quite warm in the central Rockies,” said Miller. “The implication is that alpine ecosystems respond differently to climate change than other, lower elevation ecosystems. These new results have huge implications for predicting present-day climate change in Colorado and beyond.”

Usually fossil sites preserve only snapshots in time, which are then pieced together to understand past time periods. By contrast, the Snowmastodon site captures a nearly continuous 85,000-year time span. As a result, the site provides the best-known record of life and climate at high elevation anywhere in North America.

During a total of 69 days in 2010 and 2011, the Museum mobilized one of the largest fossil excavation efforts ever, recovering more than 5,000 large bones and 22,000 small bones representing roughly 50 different species. The site is most notable for containing the remains of at least 35 American mastodons, representing both genders as well as a variety of ages, from calves to full-grown adults.

“We had no idea that the high Rockies were filled with American mastodons during the last interglacial period,” Miller noted.

While the spectacular array of Ice Age animals initially drew scientists to the site, the opportunity to understand the world that they inhabited proved to be a powerful draw as well. “Scientists from around the world donated countless hours and resources toward the project,” said Pigati. “For so many of them to come together and reconstruct a world that no longer exists in such incredible detail, well that’s just a dream come true.”

Dizzying heights: Prehistoric farming on the ‘roof of the world’

This shows the modern-day barley harvest in Qinghai, farmed at a height of 3,000 meters above sea level. – Professor Martin Jones, University of Cambridge

Animal teeth, bones and plant remains have helped researchers from Cambridge, China and America to pinpoint a date for what could be the earliest sustained human habitation at high altitude.

Archaeological discoveries from the ‘roof of the world’ on the Tibetan Plateau indicate that from 3,600 years ago, crop growing and the raising of livestock was taking place year-round at hitherto unprecedented altitudes.

The findings, published today in Science, demonstrate that across 53 archaeological sites spanning 800 miles, there is evidence of sustained farming and human habitation between 2,500 metres above sea level (8,200ft) and 3,400 metres (11,154ft).

Evidence of an intermittent human presence on the Tibetan Plateau has been dated to at least 20,000 years ago, with the first semi-permanent villages established only 5,200 years ago. The presence of crops and livestock at the altitudes discovered by researchers indicates a more sustained human presence than is needed to merely hunt game at such heights.

Professor Martin Jones, from Cambridge’s Department of Archaeology, and one of the lead researchers on the project, said: “Until now, when and how humans started to live and farm at such extraordinary heights has remained an open question. Our understanding of sustained habitation above 2-3,000m on the Tibetan Plateau has to date been hampered by the scarcity of archaeological data available.

“But our findings show that not only did these farmer-herders conquer unheard of heights in terms of raising livestock and growing crops like barley and millet, but that human expansion into the higher, colder altitudes took place as the continental temperatures were becoming colder.

“Year-round survival at these altitudes must have led to some very challenging conditions indeed – and this poses further, interesting questions for researchers about the adaptation of humans, livestock and crops to life at such dizzying heights.”

Professor Jones hopes more work will now be undertaken to look at genetic resistance in humans to altitude sickness, and genetic response in crop plants in relation to attributes such as grain vernalisation, flowering time response and ultraviolet radiation tolerance – as well as research into the genetic and ethnic identity of the human communities themselves.

Research on the Tibetan Plateau has also raised interesting questions about the timing and introduction of Western crops such as barley and wheat – staples of the so-called ‘Fertile Crescent’. From 4,000-3,600 years ago, this meeting of east and west led to the joining or displacement of traditional North Chinese crops of broomcorn and foxtail millet. The importation of Western cereals enabled human communities to adapt to the harsher conditions of higher altitudes in the Plateau.

In order to ascertain during what period and at what altitude sustained food produced first enabled an enduring human presence, the research group collected artefacts, animal bones and plant remains from 53 sites across the late Yangshao, Majiayao, Qiija, Xindian, Kayue and Nuomuhong cultures.

Cereal grains (foxtail millet, broomcorn millet, barley and wheat) were identified at all 53 sites and animal bones and teeth (from sheep, cattle and pig) were discovered at ten sites. Of the 53 sites, an earlier group (dating from 5,200-3,600 years ago) reached a maximum elevation of 2,527m while a later group of 29 sites (dating from 3,600-2,300 years ago) approached 3,400m in altitude.

Professor Jones believes the Tibetan Plateau research could have wider and further-reaching implications for today’s world in terms of global food security and the possibilities of rebalancing the ‘global diet’; at present heavily, and perhaps unsustainably, swayed in favour of the big three crops of rice, wheat and maize.

He said: “Our current knowledge of agricultural foods emphasises a relatively small number of crops growing in the intensively managed lowlands. The more we learn about the rich ecology of past and present societies, and the wider range of crops they raised in the world’s more challenging environments, the more options we will have for thinking through food security issues in the future.”

Seed dormancy, a property that prevents germination, already existed 360 million years ago

Seed dormancy is a phenomenon that has intrigued naturalists for decades, since it conditions the dynamics of natural vegetation and agricultural cycles. – UGR

An international team of scientists, coordinated by a researcher from the U. of Granada, has found that seed dormancy (a property that prevents germination under non-favourable conditions) was a feature already present in the first seeds, 360 million years ago.

Seed dormancy is a phenomenon that has intrigued naturalists for decades, since it conditions the dynamics of natural vegetation and agricultural cycles. There are several types of dormancy, and some of them are modulated by environmental conditions in more subtle ways than others.

In an article published in the New Phytologist journal, these scientists have studied the evolution of dormancy in seeds using a unique data group. This included the features of dormancy in more than 14.000 species. It is the result of Carol and Jerry Baskin’s work, the co-authors of this publication, who have been studying latency since the 60s.

The analyses conducted by this team of researchers have established that dormancy is as old as seeds themselves. In other words, the oldest among all seeds already had dormancy. ‘Of all possible types of dormancy, the oldest one already featured very sophisticated adjustments to environmental conditions”, according to the coordinator of this project, Rafael Rubio de Casas, a researcher from the Environment Department at the University of Granada, and the only Spaniard involved in this research.

Producing new species

The results of this project indicate that plants without dormancy tend to be less capable of diversification, i.e. to produce new species. “This can be due to the fact that dormancy facilitates that germination only takes place at the optimal moment, in spite of changes in the environment, due either to weather phenomena, or whether due to the fact that the seeds reach a new location after dispersal. This adjustment of the plant cycle to the new environment can reduce the probability of a particular species to become extinct”, Rubio de Casas pointed out.

Dormancy does not simply involve that seeds do not germinate when it is too hot or too cold, since under those conditions it is the environment itself which precludes germination. “What dormancy does is make sure that the seeds do not germinate even when conditions are favourable, which precludes germination after a summer storm, or during a few warm days in winter”, the U. of Granada researcher added.

However, not all plants have dormant seeds. Actually, many species of plants simply germinate at the moment when their seeds are exposed to favourable conditions. Besides, it appears that plants can acquire and lose the dormancy of their seeds in a relatively fast way as a result of natural selection.

“For instance, in the case of cultivated plants, dormancy is one of the first features that appear to have been lost over the domestication process, and for this reason the date for sowing is such an important parameter in farming”, according to Rubio de Casas.

Jurassic climate of large swath of western US was more complex than previously known

Paleontologist Timothy S. Myers, Southern Methodist University, Dallas, analyzed more than 40 ancient soil samples from three different locales in the 600,000-square-mile Morrison Formation, a massive rock unit that for more than 100 years has produced many significant dinosaur discoveries. The analysis revealed an unexpected and mysterious abrupt transition from dry to wet even though the ancient soil samples came from two nearby locales, Myers says. Click here to read more. – (Figure: Timothy S. Myers, SMU)

The climate 150 million years ago of a large swath of the western United States was more complex than previously known, according to new research from Southern Methodist University, Dallas.

It’s been thought that the climate during the Jurassic was fairly dry in New Mexico, then gradually transitioned to a wetter climate northward to Montana.

But based on new evidence, the theory of a gradual transition from a dry climate to a wetter one during the Jurassic doesn’t tell the whole story, says SMU paleontologist Timothy S. Myers, lead author on the study.

Geochemical analysis of ancient soils, called paleosols, revealed an unexpected and mysterious abrupt transition from dry to wet even though some of the samples came from two nearby locales, Myers said.

Myers discovered the abrupt transition through geochemical analysis of more than 40 ancient soil samples. He collected the samples from the Morrison Formation, a vast rock unit that has been a major source of significant dinosaur discoveries for more than 100 years.

The Morrison extends from New Mexico to Montana, sprawling across 13 states and Canada, formed from sediments deposited during the Jurassic.

Myers’ study is the first in the Morrison to significantly draw on quantitative data — the geochemistry of the rocks.

The abrupt transition, Myers says, isn’t readily explained.

“I don’t have a good explanation,” he said. “Normally when you see these dramatic differences in climate in areas that are close to one another it’s the result of a stark variation in topography. But in this case, there weren’t any big topographic features like a mountain range that divided these two localities in the Jurassic.”

Surprisingly, paleosols from the sample areas did not reveal marked differences until they were analyzed using geochemical weathering indices.

“It’s sobering to think that by just looking at the paleosols superficially at these localities, they don’t appear incredibly different. We see the same types of ancient soils in both places,” Myers said. “So these are some fairly major climate differences that aren’t reflected in the basic ancient soil types. Yet this is what a lot of scientists, myself included, depend on for a first pass idea of paleoclimate in an area — certain types of soils form in drier environments, others in wetter, others in cooler, that sort of thing.”

That didn’t hold true for the current study.

With the geochemical analysis, Myers estimated the mean average precipitation during the Jurassic for northern Montana was approximately 45 inches, 20 inches for northern Wyoming and 30 inches for New Mexico.

“This changes how we view the distribution of the types of environments in the Morrison,” Myers said. “Too many times we talk about the Morrison as though it was this monolithic unit sprinkled with patchy, but similar, variations. But it’s incredibly large. It spans almost 10 degrees of latitude. So it’s going to encompass a lot of different environments. Regions with broadly similar climates can have internal differences, even over short distances. That’s the take-home.”

Myers is a postdoctoral scholar in SMU’s Shuler Museum of Paleontology in the Roy M. Huffington Department of Earth Sciences, Dedman College.

He reported his findings, “Multiproxy approach reveals evidence of highly variable paleoprecipitation in the Upper Jurassic Morrison Formation (western United States),” in The Geological Society of America Bulletin.

Co-authors of the study were Neil J. Tabor, SMU earth sciences professor and an expert in ancient soils, and Nicholas Rosenau, a stable isotope geochemist, Dolan Integration Group.

The popular artistic representations we see today of dinosaurs in a landscape setting are based on bits of evidence from plant and animal fossils found in various places, Tabor said. While that’s based on the best information to date, it’s probably inaccurate, he said. Myers’ findings provide new insights to many studies that have been done prior to his. This will drive paleontologists and geologists to seek out more quantitative data about the ancient environment.

“The geology of the Morrison has been studied exhaustively from an observational standpoint for 100 years,” Tabor said. “I have no doubt there will be many more fossil discoveries in the Morrison, even though over the past century we’ve gained a pretty clear understanding of the plants and animals at that time. But now we can ask deeper questions about the landscape and how organisms in the ancient world interacted with their environment.”

Surprising results: Northern locale more arid than southern locale

The Morrison Formation has produced some of our most familiar dinosaurs, as well as new species never seen before. Discoveries began in the late 1800s and ultimately precipitated the Bone Wars — the fossil equivalent of California’s Gold Rush.

After Myers studied dinosaur fossils from the Morrison, he became curious about the climate. Embarking on the geochemical analysis, Myers, like scientists before him, hypothesized the climate would be similar to modern zonal circulation patterns, which are driven by the distribution of the continents. Under that hypothesis, New Mexico would be relatively arid, and Wyoming and Montana both would be wetter at the time dinosaurs roamed the landscape.

Myers analyzed 22 paleosol samples from northern New Mexico, 15 from northern Wyoming and seven from southern Montana. The samples from Montana were younger than those from New Mexico, but roughly contemporary with the samples from Wyoming.

“We found that, indeed, New Mexico was relatively arid,” Myers said. “But the surprising part was that the Wyoming locality was more arid and had less rainfall than New Mexico, even though it was at a higher latitude, and above the mid-latitude arid belt. And the Montana locality, which is not far from the Wyoming locality, had the highest rainfall of all three. And there’s a very abrupt transition between the two.”

During the Jurassic, the Morrison was between 30 degrees north and 45 degrees north, which is about five degrees south of where it sits now. Its sediments were deposited from 155 to 148 million years ago. Some areas show evidence of a marine environment, but most were continental. The mean average precipitation determined for the Jurassic doesn’t match our modern distribution, Myers said.

Study underscores that understanding climate requires multiple approaches

Previously scientists speculated on the climate based on qualitative measures, such as types of soils or rocks, or types of sedimentary structures, and inferred climate from that.

“I tried to find quantitative information, but no one had done it,” Myers said. “There are entire volumes about Morrison paleoclimate, but not a single paper with quantitative estimates. Given the volume of important fossils that have come out of the Morrison, and how significant this formation is, it just struck me as important that it be done.”

Myers classified the fossil soils according to the Mack paleosol classification, and established the elemental composition of each one to determine how much weathering the paleosols had undergone.

“There are some elements, such as aluminum, that are not easily weathered out of soils,” Myers said. “There are others that are easily flushed out. We looked at the ratio of the elements, such as aluminum versus elements easily weathered. From that, we used the ratios to determine how weathered or not the soil was.”

These findings suggest that scientists must use different approaches to quantify paleoclimate, he said.

“It’s not enough to just look at soil types and draw conclusions about the paleoclimate,” Myers said. “It’s not even enough to look at rainfall in this quantitative fashion. There are numerous factors to consider.”

Funding for the study was provided by SMU’s Roy M. Huffington Department of Earth Sciences, SMU’s Institute for the Study of Earth and Man, The Jurassic Foundation, Western Interior Paleontological Society, The Paleontological Society and the Geological Society of America.

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Note: This story has been adapted from a news release issued by the Southern Methodist University

Has one of Harald Bluetooth’s fortresses come to light?

Søren M. Sindbæk and Nanna Holm show the remains of the charred planks at one of the gateways to the fortress. – © The Danish Castle Centre

“When the discovery was published back in September, we were certain that we had found a Viking ring fortress, but since then there have been intense discussions online and amongst archaeologists about whether we were right. Now we know without doubt that we have found a fortress from the 10th century,” says archaeologist Nanna Holm, curator of the Danish Castle Centre.

Two carbon-14 dating results have removed all doubt regarding the authenticity of the Viking fortress. The carbon-14 dating was performed by the AMS 14C Dating Centre at the Department of Physics and Astronomy at Aarhus University in close collaboration with Accium BioSciences’ laboratories in Seattle.

“The two samples were both taken from the outermost tree rings of charred logs that were found in the northern gateway of the fortress. The results of the two samples are almost identical: The fortress was built in the period between the year 900 and the beginning of the 11th century,” explains Marie Kanstrup, an employee at the AMS 14C Dating Centre at the Department of Physics and Astronomy, Aarhus University.

Dating is important in determining the role of the fortress in the history of the Viking age

Søren Sindbæk, a professor of medieval archaeology at Aarhus University, explains that archaeologists are still working to date the fortress more precisely.

“We would like to determine a specific year. The carbon-14 method can’t provide that, but we are working on different methods that can help us date the fortress even more precisely.”

Dating the fortress will be an important step towards understanding its role in the history of the Viking age.

“We can’t say whether or not it’s Harald Bluetooth’s fortress yet, but now that we’ve dated it to the 10th century, the trail is getting hotter. The things we’ve discovered about the fortress during the excavations all point in the same direction. We already know that there’s a good chance that we’ll find conclusive evidence next year,” says Sindbæk.

A structure meant to symbolize power

Even though the excavations have closed for this year, the finds bode well for future efforts. The archaeologists’ investigations have also revealed that the Viking fortress was built right next to the open sea.

“The excavation showed that there was a basin of fresh or brackish water right next to one side of the fortress – presumably a quite narrow inlet leading out to Køge Bay. When the fortress was built, hundreds of tonnes of the heavy clay subsoil would have had to have been dug out into the sea basin,” explains Nanna Holm.

According to Nanna Holm, this work was undertaken for no other reason than to give the fortress an impressive location. The structure was meant to signal power.

The same master builder may be responsible

The excavation has also shown that the construction of the fortress is closely related to other Viking fortresses such as Fyrkat near Hobro, Aggersborg near the Limfjord and Trelleborg near Slagelse. These fortresses were undoubtedly built during the reign of Harald Bluetooth, and still more evidence suggests that Borgring, as the fortress has been named, might have belonged to the same building programme.

“There are a lot of similar details in these structures. And it’s been wonderful to see the same things coming to light at Borgring. In addition to the structure of the rampart and the gates, we have also found traces of a street with wood paving running along the inside of the rampart – just like in Fyrkat, Aggersborg and Trelleborg. The most striking thing, however, is the measurements of the fortress. The rampart of Borgring is 10.6 metres wide. That is exactly the same width as the rampart of Fyrkat. So it’s hard to avoid the sense that the same master builder was responsible,” says Sindbæk.
Note: This story has been adapted from a news release issued by the Aarhus University