Abstract
SUMMARY: Sedimentary cyclicity is recognised in the early Asbian (lower D1) limestones of the Llangollen district, North Wales. 14 to 15 cycles have been identified, each characterised by the alternation of two distinct lithologies. The lower phase, muddy bioclastic limestone rich in Daviesiella llangollensis, is succeeded by an upper phase of porcellanous limestone. The porcellanous limestones occasionally show subaerial features. Comparison with other areas suggests that this kind of cyclicity is commonly developed in early Asbian limestones.