Evidence of ancient meteorites found in Florida fossil clams

Posted at 1:18 PM, Jul 23, 2019
and last updated 2019-07-23 15:18:30-04

Glass beads were found inside fossil clams in a Florida quarry, and researchers believe that they’re the first particle evidence of ancient meteorite strikes in the area.

The tiny glass beads are called microtektites. They form when objects like meteorites strike the ground and spray molten debris into the air that then cools and falls to Earth in crystallized form.

Dozens of the beads were found in fossil clams at a Sarasota Country quarry. This is the first time microtektites were found in Florida and may even be the first instance of their discovery inside fossil shells, the researchers said.

The analysis was published Monday in the Meteoritics and Planetary Science journal.

In 2006, University of South Florida student Mike Meyer found the beads during a summer project in the field, working with Florida Museum of Natural History invertebrate paleontology collections Director Roger Portell.

The walls of the quarry represented a cross-section of millions of years worth of shells and geological history in the area.

The shells that the researchers found were opened and their contents run through sieves.

They were looking for shells that belonged to single-celled organisms. Instead, Meyer found 83 glass beads smaller than salt grains. They were perfectly preserved inside the shells of southern quahogs.

When these clams die, they collect particles inside their shells until sediment and materials build up on top of them, sealing the shells closed. Whole crabs and fish skeletons have also been found inside the shells.

“Sand grains are kind of lumpy, potato-shaped things. But I kept finding these tiny, perfect spheres,” Meyer said. “They really stood out.”

The beads were found in shells related to four parts of the quarry, each of which represent a different point in time.

But at the time, there wasn’t an answer available about the true nature of the beads. Meyer kept them in a box.

Now, he works at the Harrisburg University of Science and Technology as an assistant professor of Earth systems science.

“It wasn’t until a couple years ago that I had some free time,” he said. “I was like, ‘Let me just start from scratch.’ “

He conducted an analysis of their physical features and studied their elemental composition. Then, Meyer compared the beads to volcanic rock, microtektites and industrial byproducts like coal ash.

Meyer mounted the microtektites on micropaleontology slides, licking a paintbrush in order to pick up the tiny beads and placing them on small glue dots. “I did accidentally eat a couple of them,” he said.

The findings suggest that the beads are literally from out of this world. They also contain traces of exotic metals.

“It did blow my mind.” Meyer said.

The beads were probably formed during one or multiple meteorite impacts in the area, which were previously unknown. Researchers are also still puzzled by the dispersal of the beads over the quarry.

“It could be that they’re from a single tektite bed that got washed out over millennia or it could be evidence for numerous impacts out on the Florida Platform that we just don’t know about,” Portell said.

Portell believes the that microtektites could be between 2 million and 3 million years old, but the researchers will date the beads more definitively. They also contain a high amount of sodium, which is unusual because salt would normally boil off the debris once the meteorite struck and sent it up into the atmosphere.

“This high sodium content is intriguing because it suggests a very close location for the impact,” Meyer said. “Or at the very least, whatever impact created it likely hit a very large reserve of rock salt or the ocean. A lot of those indicators point to something close to Florida.”

Portell and Meyer hope that more beads can be found in Florida. But the quarry where they were found is now part of a housing development.

“Such is the nature of Florida,” Meyer said.