Correlation Tables of British Strata

Abstract

A SHORT time ago (NATURE, April 11) attention was called to the publication of Woodward's “Table of British Strata,” also issued by Messrs. Dulau and Co. The present work is in some respects far more elaborate, as it comprises nineteen detailed tables ranging from Archæan to Pleistocene. The plan of the compiler is to give the subdivisions of each formation as determined in different regions in Great Britain and Ireland. Thus, to take the Cambrian, there are columns for North Wales, South Wales, Malvern Hills, Wrekin area, Nuneaton, Northwest Scotland, and Ireland; and in these columns the various local divisions and their estimated thicknesses are given, together with references to original sources of information. No attempt is made to enumerate the characteristic fossils, the leading zonal forms—Olenellus, Paradoxides, Olenus and Dictyonenia—being the only fossils noted from the Cambrian system. In dealing with Ordovician and Silurian strata the graptolite zones receive particular attention, and other zonal fossils are mentioned. The full stratigraphical details relating to these systems make one feel that scant justice is done to the Devonian; but as a matter of fact our knowledge of that system is far less precise. Here, as occasionally elsewhere, a column for Continental divisions is given. In the Lower Carboniferous, Mr. Hobson starts with the Devon succession and places the Lower Culm Measures with the Coddon Hill Beds on the horizon of the Lower Limestone Shales, whereas their characteristic Posi-donomya and Goniatites indicate an horizon equivalent to the Upper Carboniferous Limestone or Yoredale Series. He has not, however, ventured to indicate zones in the Carboniferous, although materials have been gathered in the neighbourhood of Bristol as well as in northern counties, to which reference is made in the preface. Here and there we would suggest a greater uniformity in method: for instance, the Ammonite zones of the Lias are noted under the names Ægoceras, &c.; those of the Inferior Oolite are noted as Parkinsoni zone, &c.; and those of the Cretaceous rocks as Ammonites lautus, &c. The most difficult correlation is, doubtless, that of the Pleistocene, and here the student may well pause, for the “Upper Boulder Clay” of different areas is not to be regarded as contemporaneous. Indeed, the compiler in his preface remarks that “strata named on corresponding horizontal lines cannot, in some cases, be considered to be of corresponding age”; and the student will do well to bear this in mind.

Correlation Tables of British Strata.

By Bernard Hobson (London: Dulau and Co., 1901.) Price 5s.