On Abnormal Conditions of Secondary Deposits when connected with the Somersetshire and South Wales Coal-Basin; and on the age of the Sutton and Southerndown Series

Abstract

I. I ntroduction . M y attention has for some time been directed to the peculiar physical conditions under which many of the Secondary rocks have been deposited on the southern edge and in the interior of the Somersetshire Coal-basin, and to the remarkable evidences of unconformability everywhere present. My observations have also been extended into South Wales, where to a considerable extent the same phenomena prevail. Within the last two years I have on several occasions accompanied friends to the interesting coast-sections of Sutton and Southerndown, which have lately been the subject of a paper by Mr. Tawney, when I have pointed out that, instead of representing, as they are supposed by him to do, beds older than the Rhætic and probably on the horizon of the St. Cassian or Muschelkalk deposits, they are only abnormal conditions of the Liassic rocks which are so familiar to us in many parts of England and on the continent. Elaborate physical descriptions of some parts of the districts I shall have to notice have already been given by Messrs. Buckland and Conybeare, in the Geological Transactions*, under the title of “Observations on the South-western Coal-district of England,” and more recently by the late Sir Henry De la Beche, in a paper contained in the Memoirs of the Geological Survey, “On the Formation of the Rocks of South Wales and the South-west of England.” I shall hereafter have to refer to some interesting points not discussed in these Memoirs. II. T he M endip H ills This range of