Still, puzzling details abound regarding the end-Triassic mass extinction, such as when fern spores appeared. Ferns are often the first plants to appear after a natural disaster. But in this case, although massive quantities of fern spores coincide with lava flows in some areas, the spike occurs before the extinctions in others.
Other evidence suggested that a huge meteorite strike may have also played a role in the end-Triassic extinction event— akin to the impact that created Chicxulub crater in what is now Mexico's Yucatan Peninsula and is thought to have wiped out the dinosaurs during the Cretaceous–Tertiary (K –T) mass extinction about 65 million years ago. The giant hit that left behind the Manicouagan Crater in what is now Quebec apparently occurred about the time of the end-Triassic extinction. Research eventually showed, however, that collision was about a million years too early to have caused a die-off. But Olsen and his colleagues have investigated a crater of the right age to be the culprit—a hole about 40 kilometers wide discovered in France at Rochechouart.
Yet, a number of questions remain about the impact idea, overall, especially with regard to iridium, the relatively rare metallic element that typically accumulates as a signature layer in the geologic strata and is exposed at such sites . Scientists had apparently found multiple iridium layers, and "since multiple impacts spread over tens of thousands of years seems very unlikely, we became much less enamored of the impact hypothesis, especially because volcanic ashes can produce the same kind on anomaly," Olsen says. Over the past couple of years, though, research has also revealed that one of these iridium layers possessed ratios of other platinum group elements that were much more similar to those associated with meteorites than with most volcanic processes. The results have put the impact hypothesis back in the ring.
The researchers went digging in New Jersey looking for more fern spores, iridium traces and other potential clues that might help resolve all these questions regarding the end-Triassic mass extinction.
The region back then may have been very hot by modern standards, with climate fluctuating between humid and arid. It was covered by small-leaved conifers and was home to herbivorous and carnivorous relatives of crocodilians called the crurotars ans, in addition to small dinosaurs, lizards and the like, Olsen says. Nowadays the area is mostly rolling farmland. The researchers managed to convince the Kells to let the team drill beside the family garage, right next to a cornfield.
'The entire layer cake'
Using a Winkie is relatively inexpensive compared with the average geologic drilling project, and it can drill to a depth of about 150 meters, Olsen says.
The drill uses water for lubrication, leading to muddy jeans and sneakers all around. The engine often proved fussy, stalling when the oil– gas mix wasn't quite right. Still, over the course of a week in August, as cicadas hummed over the chainsaw buzz of the rig's motor, the researchers managed to drill down 40 meters into red mudstone. "We may have lucked out and recovered the entire layer cake—sediment layers deposited before and after the big extinction event as well as those recording the event itself," Kent says.
To see whether the suspected geologic and extraterrestrial events happened before, during and after the mass extinction, Kent will look in the core samples for signs of reversals in Earth's magnetic field, which happen periodically over hundreds of thousands of years. These reversals are captured by magnetically sensitive minerals, which preserve the way Earth's magnetic poles once pointed much like compasses. The regular nature of these reversals make them useful markers of time, and therefore help shed light on when other details found in the same rocks might have happened. By getting a better idea of when any eruptions and impacts might have occurred, the researchers hope to see what events might have directly preceded the end-Triassic mass extinction.