A colder, wetter climatic phase which followed more continental Sub-Boreal times. The change from Sub-Boreal to Sub-Atlantic conditions in Britain is roughly coincident with the transition from Bronze to Iron Age cultures. The Sub-Atlantic marks a period of renewed peat growth on bog surfaces that in late Sub-Boreal times were sufficiently dry and humified to support heath vegetation, e.g. Calluna vulgaris (ling, heather). This renewed peat growth gives a major recurrence surface, the Grenz horizon, which in Britain defines the Zone VIIb/Zone VIII (Sub-Boreal/Sub-Atlantic) boundary of the standard pollen stratigraphy. See pollen analysis; pollen zone.