University of Iowa researcher Art Bettis was back at the site to study soil strata exposed at the site.
"We're dealing with a spring deposit," Bettis said.
Some researchers had thought the Mahaska County site was a plunge pool, Holmes said.
Bettis said he was drawing samples from three sections of the dig site for analysis.
"There's wood in all three of the units," he said. Researchers can then determine the age of samples and fossils found at those levels to see if they are the same age.
Most of the bones found the past couple of weeks have come from the lower part of the dig site, Bettis said.
One of the bones found was determined to be 15,000 years old. Researchers can see how the fossil's age compares with the soil samples.
Bones found in clay will indicate where the mammoth died. However, bones found in other kinds of soil could have been washed down to their final resting places. Recently, mammoth bones were found amongst rocks, which intrigues researchers, Bettis said.
Mahaska County Conservation Board Naturalist Laura De Cook said a volunteer crew of workers were assisting the researchers Saturday.
"We have a really good crew," she said. There was enough workers for two sides of the site to be excavated.
"There's lots of good things getting accomplished," De Cook added.