A REVISED STRATIGRAPHY FOR THE WESTERN SCOTTISH LOWER LIAS

SUMMARY Formations within the Lower Lias of western Scotland are stratigraphically re-defined as a result of many new ammonite discoveries. Three formations are recognized: the Blue Lias, the Broadford Beds and the Pabay Beds. The Broadford Beds and the Blue Lias are approximately contemporary, the former (a nearshore limestone and coarse clastic facies) being restricted to the northern part of the area and the latter forming a northward extension of this formation in England and Wales, occupying the southern Inner Hebrides. The base of the succeeding Pabay Beds is recognized by its disconformable or unconformable relationship over the Blue Lias and the Broadford Beds, and it is dated at or about the turneri-obtusum Zone. The Pabay Beds continue up to the base of the massive Scalpay Sandstone, a horizon within the ibex Zone in the northern and the margaritatus Zone in the southern Inner Hebrides. New significant ammonite finds are described briefly.