Limestone containing fossils that could be about 150 million years old has been preserved at a quarry being used to store new cars, said Natural England.
Natural England was established to protect the natural environment
Staff from the agency's offices in Oxford, Aston Rowant and Berks, have restored Lyehill Quarry in Wheatley, Oxfordshire, to its former glory.
The area had been in decline for the past six years as roots from developing scrub were destroying the fossils.
It is now a site of special scientific interest (SSSI), said Natural England.
David Russell, from Natural England, said: "This is an important site in the area which we have been able to make accessible to local education groups by exposing examples of the entire sequence from the top of the Wheatley limestone to its base."
A spokesman for the agency added: "Oxfordshire is made up of extensive sections of Wheatley limestone that contains numerous fossils of mid-Oxfordian age [approximately 150 million years ago].
"Natural England had a month to restore the site while it was vacant before another tenant came in.
"Eleven members of staff volunteered to help with clearance work which involved removal of scrub, shrubs and trees.
"Cut-away areas on the rock face were treated with herbicide to prevent re-growth."
Natural England was set up last year by the Natural Environment and Rural Communities Bill to champion the English countryside.
The organisation is an amalgamation of English Nature, most of the Countryside Agency and Defra's rural development service.
It is an independent body aimed at ensuring England's natural environment is protected.
SSSIs are areas designated by Natural England as "internationally significant" and are safeguarded under European law.