On the Upper and Lower Boulder-Clays of the Gorlston Cliffs in Norfolk

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Abstract
D uring a recent visit to Norfolk, my friend, the Rev. Mr. Gunn, kindly drew my attention to a fact which cleared up some anomalies that had previously perplexed me while adopting the classification of previous observers respecting the tertiary deposits of the district, which are more ancient than the Boulder-clay. The new fact then brought to my notice, while it removes those anomalies, confirms the views which I published in 1847 of the boulder-clay being the littoral deposit of an arctic sea advancing over sinking land†. It appears that in the Gorlston Cliffs there are two boulder-clays separated by a mass of sand, which, on the authority of Woodward, has hitherto passed for the Crag, a term which has now become as indefinite as that of “drift” or “drifts.” The lower boulder-clay is the tailing-off of that so well known for its blocks of Scandinavian origin, and which extends over the north of Europe and into the eastern side of England. The upper boulder-clay is characterized by an abundance of oolitic detritus. I had traced these oolitic boulders over the south of Norfolk to the point at which they crossed the chalk-ridge of the S waffham Downs at Lopham Ford, and I had supposed that the oolitic and the Scandinavian erratics met on the same level; whereas Mr. Gunn's observations establish the fact that the former overlaps the latter, with a mass of sand interposed. In my examination of Norfolk during the three years preceding 1847, I had bestowed only

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