NA TURE 



433 



THURSDAY, SEPTEMBER 6, 1883 



NEOCOMIAN FOSSILS 

 The Fossils and Palaontological Affinities of the Neocomian 

 Deposits of Upwart and Brickhill. Being the Sedg- 

 wick Prize Essay for 1879. By Walter Keeping, M.A., 

 F.G.S. Large 8vo, pp. 167, with eight plates of fossils. 

 (Cambridge, 1883.) 



PHOSPHATIC deposits may be said to occur, in this 

 country, on all horizons from the Bala limestone to 

 the crag, yet do they most abound in the "strata below 

 the chalk," and particularly in those portions of the 

 Cretaceous system which underlie the chalk of the south- 

 east Midlands. Thus Cambridge is almost as famous for 

 its coprolites as Newcastle for its coals, and the economic 

 inferiority of the Mesozoic rocks has of late years been 

 partially redeemed, in consequence of the numerous 

 workings in these valuable beds. 



The immense collections of fossils from the several 

 "phosphate diggings," now in the Woodwardian Mu- 

 seum, afford those who have watched the growth of these 

 accumulations a splendid opportunity for studying an 

 unusually rich vein of palaeontology, and at the same 

 time of forming more correct views as to the physical 

 history of these much debated deposits. 



The coprolite beds beneath the ganlt at Upware were 

 vigorously worked some sixteen years ago, but as the 

 phosphates were inferior in quality, the work presently 

 slackened, though not before large quantities of fossils 

 had been secured by gentlemen from Cambridge, who 

 have ever been foremost in studying these and the allied 

 deposits. The workings at Little Brickhill were de- 

 scribed by the author himself in the Geological Magazine 

 (volume for 1875, p. 372), but since then the knowledge 

 of its fauna has been largely increased, " so that the 

 Brickhill bed is now only second to Upware and Far- 

 ringdon in its organic richness." Recently (1879) the 

 Upware sections have again been exposed. 



There can be no doubt that Mr. Walter Keeping is very 

 well qualified to perform the task he has undertaken, and 

 that the Sedgwick Prize Essay for 1879 must rank as one 

 of the most useful contiibutions to Neocomian geology 

 and palaeontology that has appeared in this country. It 

 is, in fact, the outcome of a long experience judiciously 

 applied. The author summarises his own work in the 

 preface, so that readers may know what they have to 

 expect : his conclusions as to the age of the ironsand and 

 phosphatic series are stated to be in near accordance 

 with the opinions of Messrs. Walker, Teall, Meyer, and 

 Barrois, "all of whom have placed the Upware bed in the 

 Upper Neocomian or Aptian series (Lower Greensand)." 

 The mammillaris zone he regards as the basement bed of 

 the gault, and to this horizon refers the Downham phos- 

 phate bed. 



The first part of the work deals with the deposits gene- 

 rally, the indigenous fauna, the " derived " fossils, the 

 British and foreign relations of the beds. The second 

 part is devoted to special palaeontology. 



In discussing the question of phosphatisation he ob- 

 serves that the nodules of Upware and Brickhill have 

 been derived, for the most part, from the Upper Jurassic 

 Vol. xxvm. — No. 723 



rocks, where as a rule the majority of the Jurassic fossils 

 are not phosphatised at all; and he concludes from the 

 similarity in the general character of the phosphate of lime 

 nodules, whether from Oxford Clay, Kimmeridge Clay, 

 or Portlandian Rock, that the phosphatic matter was 

 derivative, and all, or nearly all of one age. At page 

 30 he speaks of a coprolite heap near Ampthill, as 

 looking like one mass of Ammonites biplex, mostly worn 

 and fragmentary, whilst the Ammonites of the Oxford 

 Clay are composed of limonite, and some of the fragments 

 of fossil wood are silicified. Strangest fact of all — the 

 Coral Rag fossils from the neighbouring rock have not 

 been phosphatised in the least. The author (p. 15) 

 suggests that this purer form of carbonate of lime was 

 "uncongenial to the phosphatic matter," which would 

 have more affinity for argillaceous substances, and yet he 

 quotes the case of a stalagmitic deposit having become 

 phosphatised by percolation. 



It is not a little suggestive that whilst Ammonites biplex 

 from the Upper Kimmeridge (Middle Portlandian of the 

 French) is phosphatised in heaps, the Oxford Clay Am- 

 monites are in the condition of limonite. This seems to 

 show that original conditions have had something to do 

 with the case. Both Oxford Clay and Kimmeridge Clay 

 Ammonites and casts are often pyritised in their own 

 beds ; on the other hand, the Kimmeridge Clay as a rule, 

 especially in the Valley of Aylesbury, has all the appear- 

 ance of being rich in phosphatic matter. The process of 

 replacement, therefore, whereby the fossil cast became 

 the phosphatic nodule, may have been inaugurated during 

 the progress of denudation, assisted possibly by accumu- 

 lations of contemporary animal matter due to abundant 

 aquatic and semi-aquatic life. In this way the phos- 

 phatisation was probably completed shortly after emer- 

 gence, and the future coprolites were collected in banks 

 and shallows, to be distributed subsequently, along with 

 lydites and anything that could stand knocking about 

 by the action of waves and currents, throughout the 

 shore deposits of a slightly later period. Hence we 

 venture to suggest that the phosphatisation of the 

 Upware coprolites was effected at some distance from 

 their present billet, and thus that the fragments of Coral 

 Rag were never exposed to the temptation of having 

 their carbonic acid replaced by phosphoric. 



The principal object of the essay is of course to de- 

 scribe the indigenous fauna, and to correlate the deposits 

 generally with others of the period, whether British or 

 foreign; the similarity of the Upware and Brickhill fossils 

 to those of the Neocomian beds of the Brunswick area 

 at Shoppenstedt and Berklingen being especially men- 

 tioned (p. 73). This, together with the special palaeon- 

 tology, has been very satisfactorily worked out. We have 

 already alluded to the general conclusion based on these 

 investigations, and it only remains to notice some of the 

 more detailed matters. 



For instance (p. vi.), the author notes the close palaeon- 

 tological relationship of the ironsand and phosphatic 

 series as found at Upware, Potton, Brickhill, and Farring- 

 don, the great difference in the fauna at Potton being due, 

 he conceives, to the influence of physical conditions. He 

 further alludes to the special character of the native forms 

 of life, and to the marked preponderance of Brachiopods, 

 Polyzoa, and Sponges ; to the profusion of Brachiopod 



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