NATURE 



617 



THURSDAY, OCTOBER 25, 1900. 



THE ENGLISH GAULT AND UPPER 

 GREENSAND. 

 Memoirs of the Geological Survey of the United Kingdom. 

 The Cretaceous Rocks of Britain. Vol. I. The Gault 

 and Upper Greensand of England. By A. J. Jukes- 

 Browne, B.A., F.G.S. With contributions by William 

 Hill, F.G.S. Pp. xiv + 499. (Published by order of 

 the Lords Commissioners of H.M. Treasury, 1900.) 



TO review this book is no easy task. To select is 

 difficult when details are so full ; to criticise 

 requires one to have studied, at any rate, certain districts 

 of Cretaceous deposits as thoroughly as Mr. Jukes- 

 Browne, by whom it has been written. So, in regard to 

 the latter, we reserve the right of private judgment only 

 on one or two small matters. A slip of the pen on 

 p. 411, line 47, substituting eastern for western, and the 

 reference to the map at the bottom of the same page (to 

 a less degree) will cause a passing perplexity to readers. 

 But who can help occasionally nodding in passing five 

 hundred pages through the press ? To have included the 

 Cretaceous deposits of Scotland and Ireland, would, we 

 think, have made the subject more complete, and not 

 materially increased the number of pages. We 

 think also that Neocomian is big enough and 

 distinct enough, physically and pala?ontologically, to be 

 released from its subject position of Lower Cretaceous. 

 Surely its claims to systematic independence are 

 as good as those of Oligocene. Yet that has been 

 officially welcomed while Neocomian is slighted. Mr. 

 Jukes-Browne has, however, coined a new, though 

 more subordinate name — that of Selbornian — to include 

 the Gault and Upper Greensand, from the place hallowed 

 by the memory of Gilbert White. We confess to retain- 

 ing something of primitive man's prejudices against 

 strangers, especially in nomenclature, but must admit that 

 its author makes out a very strong case for the novel 

 term. Briefly stated it is this : During the last twenty 

 years it has been gradually ascertained that the Gault 

 and Upper Greensand in this country are not two distinct 

 stages of the Cretaceous system, but that " the greater 

 part of the Folkestone Gault and the greater part of the 

 so-called Upper Greensand are correlative deposits formed 

 at the same time in different parts of the same sea." As 

 the author shows, uncertainties in regard to their usage 

 prevent us from borrowing either ,A.lbien or Cenomanien 

 from the French, and, as a comprehensive term is so 

 much needed, we have no choice but to coin a new one. 



In a series of chapters Mr. Jukes- Browne, aided by 

 Mr. William Hill, whose services in the field as well as 

 in microscopic investigations have been of the highest 

 value, describes the Selbornian in different districts. First, 

 however, by way of clearing the ground, comes an 

 introductory chapter on the Upper Cretaceous system as 

 a whole ; a second contains an historical account of the 

 Chalk, Upper Greensand and Gault. For purposes of 

 reference, this epitome of various opinions will be very 

 useful, and has probably cost Mr. Jukes-Browne more 

 NO. 16 I 7, VOL. 62] 



labour than any other chapter in the book, for tracking 

 down misconceptions and errors is a longer business and 

 less exciting than hunting a fox, while the prey is equally 

 malodorous and worthless. A chapter follows on the 

 value of zones in the Cretaceous system, and another 

 with a general account of the Selbornian. The Lower 

 Gault, the most persistently argillaceous member, is a 

 little over 34 feet thick at Folkestone ; it increases to 

 90 feet at Devizes, is proved by borings to be 150 

 feet in Bucks, and in Bedfordshire may perhaps be still 

 thicker ; thence it thins gradually towards the north- 

 east, till at Roydon, in Norfolk, it is only 7 feet. After- 

 wards it disappears as a clay, being represented by part 

 of the Red Chalk from Hunstanton to Speeton. It is 

 separable into three zones — that of Ammonites mamtnil- 

 latus at the base, thin, sandy, perhaps sometimes 

 absent ; then that of A. i?iterruptus ; the third being 

 that of A. lautus. The Upper Gault with part of 

 the Upper Greensand, the zone oi A. rostratus, is litho- 

 logically variable, consisting of marly clays in the 

 south-east, in Bucks and in South Norfolk, it becomes 

 more sandy elsewhere (as in the Isle of Wight, and 

 especially in Dorset and Devon) while in most other 

 parts it is largely composed of the rock known as malm- 

 stone. The Warminster Beds, or the zone of Pecten 

 asper, arenaceous and containing chert, form the upper- 

 most division of the Selbornian. All have their equiva- 

 lents in the Red Chalk of Norfolk and the north-east. The 

 third and second are missing in the neighbourhood of 

 Cambridge ; while in the west the Haldon Beds begin 

 and end a little later than those of Blackdown. 



Details are given of the sections in different parts of 

 England, including those pierced by borings under London 

 and in the Eastern counties, with lists of fossils and 

 information of economic value, while Mr. W. Hill sup- 

 plies two very interesting chapters on the lithology of 

 the Gault and Upper Greensand. From these and the 

 palccontological data Mr. Jukes-Browne concludes that 

 the Gault clays were probably deposited in a sea, 

 increasing in depth from about 150 to 200 fathoms, the 

 sands of the upper part indicating stronger currents, 

 possibly without any shallowing. He also discusses the 

 physical geography of the period and the direction from 

 which the sediment came. Here perhaps he touches on 

 questions too speculative for an official publication, 

 which should be restricted as far as possible to facts and 

 to such inferences as follow directly from them. In this 

 matter, while accepting Mr. Jukes-Browne's general con- 

 clusions as to physical geography, we doubt, for that 

 very reason, whether the mud can have been brought 

 from the south-east. If the region in which it was 

 deposited was then an elongated gulf, open in that 

 direction to the sea, we are unable to understand 

 how an inflowing current of any strength could have 

 been produced. If the gulf resembled the Red Sea, 

 the inset from without would be sufficient to balance 

 evaporation but not strong enough to carry the mud 

 very far ; while if it received important rivers, the flow 

 and consequent supply of material would be from the 

 opposite direction. Mr. Jukes-Browne, it is true, refers 

 to the possibility of a return coast current from the 

 north, but we fail to see how, in a gulf of this form, the 



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