More than 100 sandstone pillars in New Mexico reaching heights of 20 feet above ground appear to be giant, fossilized termite nests roughly 155 million years old, according to new research by a team of Colorado scientists.
These probably are the worlds largest trace fossils, said University of Colorado at Boulder research associate Stephen Hasiotis, who led the study. Trace fossils -- the tracks, trails and burrows left by organisms -- help scientists reconstruct past biodiversity conditions and ancient ecosystems, he said.
The pillars, up to six feet in diameter, had previously been thought by some geologists to be fulgurites, glassy mixtures of sand and rock fused together by lightning strikes. But the new analysis indicates the pillars contain intricate, interconnected galleries and chambers nearly identical to the interior structures of some contemporary social termite nests.
Some of the fossil nests near Gallup, N.M., appear to reach more than 120 feet below the ground in places where researchers were able to trace their pathways down steep hills and cliff sides. Since some types of termites construct their nests around dead and dying tree stump and root systems, Hasiotis speculated the bottom of the fossil nests marked the Jurassic water table.
In 1996, Hasiotis reported the discovery of hundreds of smaller Jurassic termite nests in Colorado and adjoining states, evidence that termites played a major recycling role in the ecosystem at the time. These pillars are compelling new evidence that termites were well-established and more widespread in the Jurassic than we had thought, he said.
A paper on the subject was presented by Hasiotis Oct. 23 in Salt Lake City at the Geological Society of Americas annual meeting. Other authors include Fred Peterson and Christine Turner of the U.S. Geological Survey in Denver and Timothy Demko of Colorado State University.
In addition to their role as organic recyclers, contemporary termites are believed to pump about 20 million to 40 million tons of methane into the atmosphere annually. Since methane is a greenhouse gas, all these termites running around during the Jurassic and Cretaceous periods could have had a significant impact on local, regional and global climate, said Hasiotis.
The pillars were built in ancient sand dunes by the insects, which used their saliva, feces and partially digested woody material to bond the sand grains together. The fossilized nests resemble and rival the size of modern giant termite nests found in Africa and Australia today, he said.
Simple and compound galleries, or tunnels radiate out from the central nest chambers, which are as large as Frisbees, he said. There even is evidence of ancient fungal gardens in the nests as large as softballs. Fungal gardens found in termite nests today are known to regulate nest heat and humidity.
The large amount of protein available in the form of Jurassic termites might have made the towers tempting targets for ancient predators, said Hasiotis. He speculated that low-slung, armored dinosaurs like stegosaurs and anklyosaurs may have feasted on the large termite colonies.
The New Mexico fossils are not the oldest termite nests ever found. In 1993, Hasiotis and USGS researcher Russell Dubiel found fossils of 220-million year old termite nests in Arizonas Petrified Forest National Park.
The recent research effort was part of the Morrison Formation Extinct Ecosystem Project, a cooperative effort between the National Park Service, the USGS and a number of universities in the West, including CU-Boulder.
Color photos of the fossil termite nests can be accessed and downloaded from the EurekAlert news website at: www.eurekalert.org.