You all remember the train of bolids that rained down on Jupiter a few years ago? Could a train of objects come through the solar system that resulted in the great strikes of the Permian extinction event, and/or the death of the dinosaurs event which passed by close enough to Saturn or other planets to strike and kick up “dust” resulting in rings?? The Permian event falls within the age range mentioned, and since they say the rings could be newer, then it could also include the dinosaur event. Of course, possible similar events are possible that did not land on earth.
A giant wave of debris from a relatively nearby supernova, maybe.