ABSTRACT: Five coral assemblages from the Holkerian-Asbian succession at the stratotype section at Little Asby Scar, Cumbria (England) have been studied. The stratotype section is located near a fault zone, and contact of the Potts Beck Limestone (earlier Asbian) and the Knipe Scar Limestones (later Asbian) is tectonically controlled. The coral fauna of the limestone bed which defines the base of the Asbian consists of a coral assemblage which does not contain any coral taxa appearing in the Asbian. The first Dibunophyllum, the traditional coral genus for the Asbian-Brigantian, is not known until the overlying Knipe Scar Limestone. However, other coral taxa from the Knipe Scar Limestone are typical of the later Asbian. No coral assemblages can be doubtless assigned to the earlier Asbian. The coral assemblages of Little Asby Scar proved that the first appearance of Siphonodendron junceum is in the upper Asbian. The distribution of other important biostratigraphic groups, the foraminiferans and brachiopods, supports a relocation of the originally defined Holkerian-Asbian boundary. However, the bases of the biozones of the two most abundant groups, corals and foraminiferans, do not coincide; Asbian foraminiferans appear earlier than Asbian corals. The attempt to correlate the Little Asby Scar succession to the Belgian Namur-Dinant basin and its standardized sedimentary sequences based on a simple presence-absence comparison of corals and foraminiferans does not result in a definite correlation. It is evident that the Holkerian-Asbian boundary as originally defined is lithostratigraphic, and that the absence of any biostratigraphic support prevents the use of that level in a chronostratigraphic context. Therefore, after a consensus on the criterion for the base of the Asbian, the stratotype section should be relocated to a better exposed section.
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