Florissant Tops Amber Deposits For Fossil Beetle Richness, According To CU-Boulder Study

Widely noted for its ability to capture and preserve diverse insect remains in an aesthetically pleasing way, amber has become popular with naturalists, jewelers and filmmakers, said CU Museum paleontologist Dena Smith. But a fossil beetle database gleaned from major sites around the world by Smith shows the Florissant Fossil Beds have produced more beetle species and families than the total from all amber sites worldwide.

“Amber seems to be the big, exciting thing lately because it is beautiful and was highly publicized in Jurassic Park,” said Smith. “But I was surprised to find that Florissant is not only better than any single amber deposit, it’s better than all the amber sites in the world combined.”

Smith presented her findings at the annual Geological Society of America meeting held in Denver Nov. 7 to Nov. 10.

Formed 34 million years ago when volcanic eruptions blocked a major river basin to form a huge lake, the Florissant region has yielded more than 1,500 different fossil insect species, including 566 beetle species. This compares to 508 beetle species from the 14 beetle-bearing ambers known in the world, and just 183 species from any single amber locality, according to Smith’s database.

The shale at Florissant Fossil Beds National Monument has yielded fossils from 53 different beetle families, said Smith. In comparison, Saxon amber from Europe, which has the greatest beetle family diversity of any amber deposits in the world, has representatives from 44 beetle families.

Although amber deposits containing fossil insects are found worldwide, some of the best known are Baltic and Saxon amber in Europe, Dominican Republic amber and Lebanese amber, she said. At those deposits, unlucky ants, flies, bees and beetles became stuck in the sticky resin produced by the branches and trunks of trees, which later turned to amber and froze them in time.

“Amber is better at trapping smaller insects, primarily those specialist species attracted to dense, forested environments,” said Smith. “Florissant was a warm, temperate lake environment that hosted a wide variety of aquatic insects, as well as many insects that are well adapted to flying in open areas.”

The Florissant insects were preserved through carbonization, a process that preserves organisms as films of carbon. Although it is a one-dimensional process that takes place over time in paper-thin shale, the preservation elegantly captures the insect features down to antenna and wing patterns, said Smith.

“The climate was just beginning to shift toward the temperate conditions that exist today, so it was an important time period of change,” she said.

Florissant also has produced a much wider range of fossil beetle size-classes than amber, Smith said. The size of beetles at Florissant range from 1-24 millimeters, compared to 1-13 millimeters for amber beetles.

Much of the pioneering work on fossil beetles at Florissant was done by English entomologist T.D.A. Cockerell, who came to Colorado in 1906 seeking relief from tuberculosis. Cockerell, who became a University of Colorado professor and helped to found the CU Museum, published more than 40 papers on the Florissant fossil insects and laid the groundwork for future research.

“It is exciting to go through the collections, because Cockerell often used to write his field notes right on the rocks containing fossils,” Smith said.

Florissant is experiencing a renaissance of sorts, with dozens of CU-Boulder students set to conduct research there in the coming years. “After 100 years of research at Florissant, we still are learning new things today,” she said.