Microscopic fossils collected by Harvard researchers from the Red Line subway extension in Cambridge recently resolved a 100-year controversy and revealed that the Boston Basin is 6 million centuries old.

Discovering the age of the basin will enable scientists to "reconstruct the geological series of events" that occurred during the pre-Cambrian era, when the Basin was formed. Paul Strother, a post-doctoral fellow in Biology and one of the discoverers, said yesterday.

"It was a coincidence that evidence from our back door," a post-doctoral fellow in Biology and one of the discoverers would yield fossils" proving that the area was much older than previous estimates, Strother added.

The Basin extends from Boston' Harbor to a ridge of volcanic rocks running from Milton north to Lynn and westward to Route 128. The discovery, which is formally announced in the May 7 issue of Science magazine, solves a "mystery plaguing us for over 100 years," said Elso S. Barghoorn. Fisher Professor of Natural History and another participant in the year-long research project.