A swath of bedrock in northern Quebec may be the oldest known piece of the earth’s crust.

In an article appearing in Friday’s issue of the journal Science, scientists report that portions of that bedrock are 4.28 billion years old, formed when the earth was less than 300 million years old.

“These rocks paint this picture of an early earth that looked pretty much like the modern earth,” said Richard W. Carlson of the Carnegie Institution of Washington and one of the authors of the paper.

Other scientists are intrigued, but not yet entirely convinced that the rocks are quite that old.

“There is a certain amount of healthy skepticism that needs to play a role here,” said Stephen J. Mojzsis, a professor of geological sciences at the University of Colorado. Dr. Mojzsis said the new research was well done, but that he thought these were younger sedimentary rocks, pressed together out of the remnants of earlier rocks that were indeed 4.28 billion years old.