The Fröjel Formation is a ten-metre thick siliciclastic unit lying in the carbonate sequence of Gotland, Sweden. Deposited some 424 million years ago during the mid Homerian (late Wenlock, mid Silurian), the sediments represent an unusually high supply of terrigenous sediment into the shallow carbonate platform that was to become the island of Gotland. Their deposition is coincident with a δ13C excursion of +3‰.