Researches in newer pliocene and post-tertiary geology

Preface

I have been induced to collect into one volume a series of papers on the more recent geological deposits, the result of upwards of thirty years' observations, conducted chiefly in the basin of the Clyde, a locality the richest with which I am acquainted in the fossils of the glacial period. They were communicated to different Societies, published in different Transactions, and in some cases given only in abstract. They are now printed in full as they were originally read, with the exception of the Catalogues of Recent and Sub-fossil Shells, which I have enlarged so as to comprehend the discoveries made since their first publication ; and I have endeavoured, by notes, to point out how far my conclusions have been modified by subsequent researches. In order to judge of the soundness of these modifications, I must ask the reader to bear in mind the dates of the papers and the state of our knowledge of the superficial deposits when they were written.

In addition to the advantages of residing in a rich loca lity, I have to acknowledge that of the personal assistance of such naturalists as Dr. Scouler, Captain Brown, the late Mr. George B. Sowerby, Edward Forbes, and the Rev. Dr. Landsborough, when accompanying me in my dredging cruises. b

PREFACE.

. VI I mention them in the chronological order in yhich they assisted me. I had hoped at one time to have been able to add to the list the name of my friend, Sir Charles Lyell; but although I had not the good fortune to have his assistance in the field, I have had, from the very beginning of these researches, the benefit of his advice, and the encouragement afforded by the interest he took in their prosecution. I have made use of his terminology in distinguishing the latest tertiary from the recent or post-tertiary. In the note at page 26 I have expressed doubts as to whether the Clyde Arctic should be included in the newer pliocene; but as these doubts never can be entirely removed, in consequence of tbe loss of some of the unknown shells, of which only one speci men was found, I adhere to the original classification.

In the paper on the relative ages of the tertiary and post tertiary deposits of the Clyde (No. VI.), I have classed the tertiary with " the newer pliocene, or pleistocene, of Lyell," (p. 79.) I did so because he wrote to me that it was his in tention to make use of the term " pleistocene," in place of newer pliocene, in designating these beds. That intention he has, as I think, rightly given up, for it would preclude the use of the expression " older pliocene," which, in some cases, may be necessary, especially in classifying the Italian and Sicilian pliocene, just as I found it necessary to use the term " older miocene " in a paper on the Lisbon tertiary. The term has since been made use of by Edward Forbes, to desig nate beds of the same age as those of the Clyde, which he has also termed glacial. I have to express my best thanks to John Buchanan, Esq., of Glasgow, for permission to include in the Appendix

PREFACE.

. VII his elaborate paper on the Glasgow canoes (No. IV.), which is scarcely less valuable in a geological than it is in an archæological point of view, by showing that great changes of level must have taken place during the human period. I am also indebted to John Buchanan, Esq. of Ardoch, for having at my request drawn up an account of the great debacle at Martigny in 1818 (No. III.), which it was his good fortune to witness, and to escape with his life. The illustrations owe much of their value to the graphic pencil of my friend, Andrew Macgeorge, Esq. His sketches were taken upon the spot, with the intention of elucidating the subjects of the papers. And lastly, I have to express my obligation to T. F. Jamieson, Esq. of Ellon, for having furnished me with a Catalogue of the Aberdeenshire Glacial Shells.

In the papers on Madeira and Gibraltar, the fundamental rocks no doubt belonged to the older formations; but in each my object was to describe the subsequent changes, many of which must, and all of which may, have taken place during the newer pliocene or post-tertiary periods. JoRDANHIisL, October, 1862. CONTENTS. Page I. — On Indications of Changes of Level in the AVest of Scotland, 1 II. — On the Last Changes in the Relative Levels of Land and Sea in the British Islands, 6 III. — On the Phenomena of the Elevated Marine Beds of the Basin of the Clyde, 28 Catalogue of Shells from the Glacial Deposits of Britain and Ireland, ........ 46 Shells from the Mammaliferous Crag, in the Catalogue of E. Forbes, 56 Shells not found Fossil in the British Islands, from the Catalogue of E. Forbes, 57 List of Marine Shells in the Glacial Beds of Aberdeenshire, 57 Catalogue of the Recent Marine Shells of the Frith of Clyde, . . .59 IV. — Notices of the Newer Pliocene Deposits in Scotland and the Western Islands, 65 V. — On the Climate of the Newer Pliocene Tertiary Period, . 71 VI. — On the Relative Ages of the Tertiary and Post-Tertiary Deposits of the Basin of the Clyde, . . . .76 VII.— On the Geology of the Island of Madeira, . . .85 VIII.— On the Geology of Gibraltar, 98 IX.— On Recent Depressions in the Land, . . . .115 CONTENTS.

X Page X.— On Scratched Boulders, . . . . . .127 XL — On the Occurrence of Marine Shells in the Stratified Beds below the Till, 139 XII. — On a Split Boulder in the Island of Little Cumbrae, . 144