Pliocene bryozoans in the Suffolk Coralline Crag

Paul D Taylor and Rory Milne (UK) Britain is not richly endowed with fossiliferous Pliocene localities. However, the Red and Coralline Crags of East Anglia make up for this deficiency in the sheer abundance and quality of their fossils. Whereas the Red Crag, famous for its gastropods and bivalves, takes its name from the colour of the sediment, the Coralline Crag is named for its ‘corallines’. But what exactly are these? Despite the name, which suggests corals or perhaps coralline algae, the corallines of the Crag are actually bryozoans, popularly known as ‘moss animals’ or ‘sea-mats’ (see Issue 12 of Deposits: Bryozoans: more than meets the eye). In fact, the Coralline Crag is a bryozoan limestone and represents a rare example of a non-tropical limestone in the British geological record. The main outcrop of the Coralline Crag runs between Gedgrave near Orford in the south, to Aldeburgh in the north, forming a low ridge almost parallel to the Suffolk coast (Fig. 1). There are also small outliers further south at Sutton and Tattingstone, but the latter is now submerged beneath a reservoir. Lateral equivalents of the Coralline Crag can be found in Belgium and Holland (for example, see Bishop & Hayward 1989). Fig. 1. Outcrops of the Coralline Crag in Suffolk (shown as yellow).Deposition occurred in shallow water, about 4Ma, along the margins of the ancient North Sea. Giant submarine dunes – sandwaves – swept the fragmented remains of bryozoans and other shells along the seabed, leaving behind the spectacular, … Read More