sentences:  Some pebbles contain microfossils of marine animals (Lingula lesueuri and Orthis budleighensis) which can be traced to the same source area in the Armorican Massif.Pebbles of Carboniferous limestone and reworked earlier Triassic sandstones indicate their source as being from the South Derbyshire area and the Clent Formation south of Birmingham respectively.There is further evidence from the distribution of the pebbles themselves, the average size of the stones on the southern margin of the basin is noticeably larger than that to the north, which is consistent with a flow of water from the south.