568 



J. P. BLAKE ON THE UPPER 



only 17 out of 58 are common. If, then, by stratigraphy, by 

 palaeontology, and by common consent, the rieuvizy ironstone 

 and its equivalents are to be placed as the summit of the 

 Oxfordian, the English classification must be modified to bring it 

 into harmony with more widely-established facts. It has been seen, 

 in former studies of our English Corallian rocks, how readily they 

 lend themselves to such a change by the "markedly Oxfordian 

 character of the fauna " of their lower part. It is proposed, there- 

 fore, to abolish the term " Lower Calcareous Grit," as associating 

 the rock intended too closely to the " Upper Calcareous Grit," and, 

 as it forms an integral part of the Oxfordian series, to call it the 

 " Oxford Grit," and, for some part at least of the overlying lime- 

 stones, to revert to the old name of the " Oxford Oolite." These 

 terms, however, are too descriptive to be generally applicable, and, 

 when they are not so, may be replaced by the more general term 

 " Upper Oxfordian." 



"We may now trace the range of this mass over the area 

 studied. The Ferruginous Oolite of jNeuvizy has been placed as 

 the Lower Oxfordian by Oppel (27), partly in reliance on Prof. 

 Hebert's erroneous section (21), which places a mass of clay 

 above it, partly by placing the Cidaris-florigemma beds as Upper 

 Oxfordian, but chiefly by including the whole of the underlying clay 

 in the same subdivision, and thus quoting true Oxford-Clay fossils, 

 which are not to be found in Buvignier's lists, such as Amm. biarmatus 

 and Amm. Henrici. Oppel does not, however, quote Amm. Lamberti, 

 which is most characteristic of Oxford Clay. There is not sufficient 

 evidence, therefore, to overcome the weight of that obtained from 

 the list of fossils given above, which places this ironstone as the 

 uppermost part of the Oxfordian, as it is stratigraphically by its 

 immediately underlying the Cidaris-florigemma beds. Along the 

 whole of the Eastern range, the Oxford Grit below remains constant, 

 becoming more nodular to the south : and the ironstone reaches 

 nearly as far. The only deposit hereabouts which can give rise to 

 any dispute is the limestone ; of Creue and Liouville, the highly 

 Oxfordian character of the fossils in which has led Hebert (21) to 

 place it in the Oxfordian ; while Buvignier (22) makes it Corallian. 

 Palseontologically, it is undoubtedly more united to the Oolite below ; 

 but by its extremely local character, and its alternating with the 

 Rag above, it belongs more to the latter, and must therefore be left 

 as on a kind of neutral ground. 



On the change of strike and on crossing the band of Lower Jurassic 

 rocks which extends to the south, we find a change in the development. 

 Grits and ironstones can no longer be found, but the rocks continue 

 to be marly as below ; while a new set of Ammonites characterizes 

 the upper part, though the general facies remains the same, the true 

 Oxford Clay, with Amm. Babeanus and Amm. Lamberti and others 

 belonging to the group Harpoceras remainiDg constant. Below, it 

 would appear that the beds which intervene between these and the 

 Corallian, with their Ammonites continuing from below, as Amm. 

 marantianw&c, occupy the place of the Oxford Oolite and Oxford Grit, 



