Essex (TM 266234-TM 266238)
The rapidly eroding cliffs north of Walton-on-the-Naze expose up to 9 m of the type ‘Waltonian’ Red Crag resting unconformably on the London Clay. A discontinuous lag deposit, consisting mostly of rounded, polished phosphatic mudstone pebbles with very occasional ‘boxstones’, marks the unconformity. The main part of the Red Crag above consists of quartz-rich sands containing mollusc shells often concentrated in bands. Indigenous encrusting bryozoans can be found on the interiors of some of the bivalve shells, while red-stained bryozoans derived from the Coralline Crag are not infrequent. Decalcification characterises the top of the Red Crag.
Adapted from Daley and Balson, 1999.