XV.— A Note on the Base of the Lias near Broadford, Skye

Abstract

As further work on the Jurassic rocks of Skye is likely to be delayed it may be useful to record the results of observations made at Lusa Bay, near Broadford, several years ago. The section is well known and has been described or referred to by Macculloch, Murchison, Hugh Miller, Geikie, Judd and H. B. Woodward: a general account by the latter in the Geological Survey memoir (1910) gives adequate references and summarises the succession. The lower part of the Lower Lias (the Broadford Beds) is there divided into four subdivisions; the uppermost yields Arnioceras and Coroniceras, and a great abundance of Gryphaea incurva. There is little doubt that this group belongs to the upper part of the Bucklandi Zone ( s. lat. ). Dr. L. F. Spath has more recently emphasised that the reference of the upper part of these beds to the Semicostatum Zone is inappropriate (1922); correlation with other areas (as with the Loch Sligachan and Heast districts) is certainly facilitated when it is recognised that the beds with Arnioceras are not higher than the Bucklandi Zone. The age of the underlying subdivisions has been in doubt owing to the absence of ammonites. In the memoir referred to the ‘passage beds’ immediately overlying the Trias (about 4 feet thick) were doubtfully referred to the Rhaetic, but the palaeontological evidence is not convincing (Lee and Pringle, 1931, p. 170). The presence of the Angulata Zone below the Bucklandi Zone has been inferred, and Dr. W. J. Arkell has suggested that This 250-word extract was created in the absence of an abstract