Fossilized feces from 73 million-year-old aquatic life found on Devon Island in the Arctic Circle suggest an ancient marine ecosystem teeming with bottom-feeding creatures, according to a University of Colorado at Boulder researcher.
Such a scenario is similar to modern Arctic marine environments where excess nutrients generated by huge pulses of plankton growth in the summer drop to the bottom of the ocean where they can be eaten over time.
Assistant Professor Karen Chin, of the CU Museum and geological sciences department at CU-Boulder, will present her findings at the annual Geological Society of America meeting held Nov. 7 to Nov. 10 in Denver. Chin will give her presentation on Tuesday, Nov. 9, at 3:30 p.m.
Many of the specimens of fossilized feces, or coprolites, that she found and analyzed from a site on Devon Island within the Arctic Circle contain high concentrations of sand.
"The high sand content in these specimens points to a lot of feeding on the sea floor," Chin said. "So far we haven't found a lot of fish bones in the feces, which suggests that at this point in time fish and other vertebrates were focusing on bottom-dwelling organisms."
She also found some coprolites from large marine animals loaded with microfossils, suggesting a diet of plankton or plankton eaters. Others contain the remains of bottom-dwelling mollusks and lobsters that were well preserved and clearly evident in the feces.
Many of the coprolites also were highly burrowed, which means there also were plenty of hungry mouths at the bottom of the ocean in this ancient near-shore marine ecosystem.
"To these bottom-dwelling creatures, the feces were like a windfall from above," Chin said.
Working with Assistant Professor Jaelyn Eberle, also of CU-Boulder, Chin traveled to Devon Island in 2002 and collected more than 400 coprolites. In 1998, Eberle discovered fossils of plesiosaurs-giant sea creatures resembling the mythical Loch Ness Monster with long necks and flippers, along with shark teeth, ancient fish and fossils of diving birds.
"Finding these body fossils in the same sediment suggests that they are good candidates to be the coprolite producers," Chin said.
Chin, one of the world's leading experts on coprolites, says coprolites often contain a treasure trove of information about ancient species and their ecosystems, including what everybody was eating and who was present at the table. They contain so much information, she said, because fecal matter can sometimes turn to rock in a matter of weeks, preserving the waste from the producer's last meal.
Determining what is or isn't a piece of ancient excrement can be tricky, according to Chin. Some are pretty obvious just by looking at them, she said, but in others you have to look for telltale clues. Chin looks at their shape, chemical composition and the presence of chopped up material to make her determination.
"Dung eating organisms leave traces, so I also look for burrow marks in the coprolite," Chin said.
Seventy-three million years ago Devon Island was nearly at the same latitude as it is now, which means during the summer there was 24 hours of sunlight and during the winter there was no daylight. While she has learned a great deal about the marine environment off the coast of Devon Island, there are still many unanswered questions.
"What we're trying to do is look at the whole picture of the animals that were there at the time and the patterns of energy flow, which defines the ecosystem," Chin said. "These creatures' quest for energy is what binds the members of an ecosystem together."
Chin worked cooperatively with Eberle and Justin Tweet of CU-Boulder, John Bloch of the University of New Mexico in Albuquerque and Stephen Cumbaa of the Canadian Museum of Nature.