The Sailing Stones is a great name for a band, but an even better name for a geological mystery that has baffled observers for many decades. As their name implies, ‘sailing stones’ refers to large boulders that mysteriously move on their own across flat surfaces, leaving a telltale track in the mud behind them. While they’ve been observed in Nevada, Spain and a few other area, the most famous are at the Racetrack Playa in California’s Death Valley National Park. The invisible force moving those rocks was finally solved in 2014 (more on that later), but a new sailing stones mystery popped up this week when a paleontologist revealed a track on a 200 million-year-old fossil found in Connecticut and thought to have been made by a dinosaur is actually evidence that the mystery has been around for eons. Connecticut?
“A remarkable 3.4 m Early Jurassic sandstone slab on display at Dinosaur State Park, CT preserves a large shallow trough with grooves closely comparable to those made by “sailing” rocks. The slab also contains the trackway of a large basal sauropodomorph dinosaur (Otozoum moodii) with well-preserved pedal scale impressions, as well as a completely new type of tiny trackway attributable to a bounding or hopping stem-mammal.’"
In a presentation at the recent 2019 Fall Meeting of the American Geophysical Union (AGU), paleontologist Paul Olsen from Lamont-Doherty Earth Observatory, part of Columbia University in New York, told of the mystery of a sandstone slab that has been on display for over 100 years at Dinosaur State Park, an unexpected treasure trove of dinosaur tracks in Rocky Hill. Discovered in Connecticut, the slab contains footprints of a Brontosaurus-like dino from the Early Jurassic period and a strange trail or streak that was overshadowed by the prints and ignored. (Image can be seen here in press release.)
That changed in 2017 when Olsen and colleagues recognized the streak as the track of a 200-million-year-old sailing stone. How could this have happened? The sailing stones in Spain are attributed to thick layers of microbes that allow the stones to slide, but the Dinosaur State Park slab showed no signs of microbes. In 2014, it was determined that the sailing stones at the Racetrack Playa moved when extremely thin sheets of ice formed. As the ice cracks and forms large panels, winds hit the rocks hard enough to turn them into sails that propel the ice panels, leaving an indentation underneath them. Could that perfect-ice-storm combination have happened 200 million years ago in Connecticut?
“There are no reasons to think that freezing would be a normal situation there.”
Olsen points out that this sailing occurred at a time when what is now Connecticut was at the same latitude as today’s Yucatan peninsula and had a tropical climate. In light of that, Olsen proposes a different perfect storm – one caused by a volcanic winter. Many scientists believe the Permian Extinction, which occurred 252 million years ago, was caused by massive volcanic eruptions in what is now Siberia. The clouds and sulfur gases they created could have caused brief periods of global cooling which may have formed ice sheets in tropical areas thick enough to slide stones but not long-lasting enough to kill the dinosaurs whose footprints were found alongside the sailing trail.
Plausible? Sure, but Olsen plans to look for stronger evidence – like more sailing stone tracks.
“If you could find them moving in synchrony, that would really indicate that it was ice, without a question.”
Perhaps he’ll also find out if the dinosaurs and mammals were afraid of the sailing stones or if they stood around watching them … and wondering if those strange pale apes would ever figure out their cause.