Age of a storm
The age and nature of the material make tsunami verification a challenge.
The radiocarbon dates of the debris are accurate to within a century, said Dr Goodbred. But the only evidence that a dramatic event took place thousands of years ago is common coastal debris - wood, sand, shells and rock.
Researchers must discern whether it was strewn by a tsunami or a hurricane, or another large storm, such as a "nor'easter", said Professor Driscoll.
Unusual layers in sediment cores
may be a sign of an ancient tsunami
"Understanding the origins of these deposits can be difficult," he added.
While tsunamis can occur in any ocean, they are most common in the Pacific and Indian Oceans where continental plates collide.
There, large undersea earthquakes are relatively common.
In the Atlantic, where the plates spread, tsunamis are rare, which means Atlantic tsunamis are not well studied, said Bruce Jaffe, of the United States Geological Survey.
There is little research on tsunami debris in the variety of northeast coastal environments - riverbeds, marine bays - where the New York debris layers were found. There are few modern analogues to compare them with for identification, he said.
"Grand Banks is the only unequivocal tsunami in the Atlantic on the Northeast coast because there were eye-witness accounts and the deposits matched that of other modern tsunamis," said Dr Jaffe.
To rule out the possibility of a severe storm, said Professor Driscoll, tsunami groups should collect more core samples to see whether the distribution of the debris is consistent.
Dr Goodbred said teams were planning to do just that. And this would confirm that the deposits are not quirks of local geology.
