Page:Quarterly Journal of the Geological Society of London, vol. 27.djvu/626

 Conclusion.

Nothing can be clearer than the relation of the Red to the Coralline Crag ; but the Norwich Crag occupying a different area, and each area presenting a crag-series of its own type, without superposition or passage, their relation to one another must necessarily be established on other grounds. We have to see what other beds there may be common to the two districts, whether in each they bear a like relation to those Crag beds which are the object of inquiry, and whether the differences known to exist in the latter may not be owing to geographical distribution.

In this case we have the one common bed in the Chillesford Clay, which forms a zone limiting in ascending order the position both of the Red and of the Norwich Crags, both of which it overlies and with both of which it shows a close relation. But although we can follow the Chillesford Clay (retaining its usual characters and fossils) into the southern part of the Norwich-Crag area at Southwold, north of that district it is not fossiliferous and we can only identify it by position and mineral characters. Nevertheless we can follow this argillaceous zone, although a character of uncertain value, with sufficient clearness to Bacton and Weybourne, and also inland to Norwich and Coltishall. In Norfolk, however, as the sands and shingle overlying the Chillesford Clay become interstratified with beds of laminated clay very similar in appearance to the Chillesford Clay, it might be a question whether the bed which I have referred to that deposit in Norfolk belongs to it, or whether the Chillesford Clay is represented by the Laminated Clays of Mr. Gunn. Mr. Gunn contends that such is the case. Although I am ready to admit that, on lithological characters alone, the evidence would be almost as good for one as for the other, still I think that the clear superposition of the Chillesford Clay to the Crag, and its infraposition to the Westleton shingle, at Easton Bavent, with the commencing indications of the Forest-bed at the same place, and its clearer exhibition at Kessingland, accompanied by the setting in, in the same cliff, of the Elephant-bed — taken in conjunction with the presence of the Mastodon in the Norwich Crag and its absence in the Forest-bed, and the difference in the species of Elephant, Rhinoceros, Deer, &c. in the two series — sufficiently prove their relative position and age. Mr. Gunn's Laminated Clays constitute a subordinate lithological character of the Westleton series in Norfolk, and are occasionally present in Suffolk.

The Forest-bed, of which we get indications at Easton Bavent, is more fully developed at Kessingland and Corton, at which latter place it passes under the lower division of the Boulder-clay, the Westleton shingle having been denuded as it occasionally has been even in the Hasborough and Mundesley district (see fig. 36, p. 465). At Hasborough and Bacton the base of the Westleton shingle is usually cemented into a hard " pan " by oxide of iron, and constitutes the well-known Elephant-bed. This reposes upon the Forest-bed, which, in its turn, rests on the Chillesford Clay when