On the Punfield Formation

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Abstract
Conclusion: The grounds on which I have ventured to suggest that the strata, the nature and relations of which I have endeavoured to illustrate in the preceding pages, are worthy to rank as an independent formation are as follows:— 1. They present very distinct mineralogical characters, separating them alike from the overlying Neocomian and the subjacent Wealden proper. 2. They are of considerable thickness, attaining a maximum of 230 feet. 3. They present evidence of having been deposited under conditions differing alike from those of the marine Neocomian above and the purely freshwater Wealden below. 4. They yield a considerable marine fauna (between 30 and 40 species being already known), which is remarkably distinct and well characterized. 5. They are the undoubted representatives of a formation which in Spain attains to a vast thickness, and which, alike from its marked palæontological characters and its great economic value, is of great importance. 6. Their relations to the Wealden and Neocomian are precisely analogous to those of the Purbeck formation to the Oolite and Wealden; and they are therefore equally deserving with it of a distinctive title. At the same time I have endeavoured to show that these beds may be regarded indifferently either as the highest member of the Wealden in our classification of the series of terrestrial strata, or as a portion of the Neocomian in our grouping of the marine series. The application to them of a distinctive name is therefore, although a necessary, perhaps only a provisional expedient; but the same is to a greater or less extent true of most of our geological terms.

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