The rings on Saturn change so rapidly that they must have formed quite recently, on the order of millennia and they've generally been thought to be the oldest of the planet rings.
The age and fate of Saturn’s rings
As the article says, Saturn's rings were long assumed to be about 4.6 billion years old. Yet a new ring, the 'C' ring, has apparently come into existence since telescope observations of Saturn's rings began. This must be due to dissipation of the 'B' ring.
Thus one of the three prominent rings of Saturn has evidently developed since the early 1800s. The inner edge of the C ring is approaching the planet, and Napier and Clube calculated the rate of approach as 100 km per year.
The history of C ring observations implies rapid ring spreading and dissipation. The inner edge of the B ring is now 91,975 km from the center of Saturn and the inner edge of the C ring is at 74,658 km.44 Thus the width of the C ring is 17,317 km, or about 15,000 km, a width which developed since about 1850. This implies an infall of ring particles in agreement with the computation of Napier and Clube.
I should say the ‘C’ ring is due to SPREADING of the ‘B’ ring.