WorldWide Drilling Resource®

18 AUGUST 2020 WorldWide Drilling Resource ® Cosmic Pearls? Adapted from Information by Florida Museum of Natural History When student researchers from the University of Florida were picking through fossil clams from a Sarasota County quarry, they found something they certainly weren’t expecting, dozens of tiny glass beads. Could these glass beads be microtektites? Microtektites are nonvolcanic, grain-sized silicate glass formed when a meteorite slams into the earth. This would be the first documented discovery of microtektites in Florida, and possibly the first to be recovered from fossil shells. As an undergraduate at the University of South Florida, Mike Meyer discovered the glass beads during a 2006 summer fieldwork project. The project, led by Roger Portell, invertebrate paleontology collections director at the Florida Museum of Natural History, allowed students to collect fossils from shell-packed walls of the quarry, of- fering them a unique sample of Florida’s geological history over the last few million years. They pried open fossil clams and washed the sediment inside through very fine sieves to sift through the contents. Although Meyer was initially looking for shells of a single-celled organism called benthic foraminifera, he began noticing translucent glassy balls, smaller than grains of salt. “They really stood out,” said Meyer, who is now an assistant professor of earth systems science at Harrisburg University in Pennsylvania. “Sand grains are kind of lumpy, potato-shaped things. But I kept finding these tiny, perfect spheres.” After the fieldwork ended, his curiosity about the spheres persisted, but he was unable to find anyone who knew what they were. He kept 83 of the spheres in a small box for more than a decade. “It wasn’t until a couple years ago that I had some free time,” he explained. “I was like, ‘Let me just start from scratch.’” Meyer analyzed the elemental makeup and physical features of the spheres and compared them to volcanic rock, microtektites, and byproducts of industrial processes, such as coal ash. He discovered the tiny beads were actually mi- crotektites. He thinks they formed as a result of one or more small, previously unknown meteorite im- pacts, potentially on or near the Florida Platform, the plateau bracing the Florida Peninsula. Most of the beads were found inside fossil Mercenaria campechiensis or southern quahog shells. As Portell explained, when clams die, fine sediment and particles wash inside. As more sediment settles on top of the clams over time, they close, becoming excellent long-term storage containers. “Inside clams like these we can find whole crabs, sometimes fish skeletons,” he said. “It’s a nice way of preserving specimens.” During the 2006 project, the students recovered microtektites from four different depths in the quarry, which is unusual since each layer represents a distinct period of time. “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,” Meyer explained. One of the strange things about these microtektites is they contain high amounts of sodium. Since salt is highly volatile and generally boils off if thrust into the atmosphere at high speed, the high sodium content suggests a very close location to the impact. “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,” Meyer said. Meyer and Portell suspect there are more microtektites awaiting discovery in Florida and have asked amateur fossil collectors to keep an eye out for the tiny spheres. Unfortunately, no one will be recovering microtektites from the original quarry location as it is now part of a housing development. MIN Photo of microtektites by Meyer. Researchers plan to date the microtektites. Portell’s guess is they are between 2-3 million years old. Photo by Kristen Grace courtesy of Florida Museum. Mike Meyer made the discovery during a quarry excavation project in 2006. Photo courtesy of Mike Meyer. In between print issues, the WWDR Team prepares an electronic newsletter called E-News Flash . This newsletter is filled with articles not included in our print issue. Based on readership, this was the most popular article of the month. Get in on the action and subscribe today at: