Vol. 62.] PHOSPHATIC CHALKS OF WINTERBOURNE AND BOXFORD. 521 



beds of Marsupites- and later age from the early Eocene planation is 

 due, in no small degree, to differential earth-movements taking place 

 either soon after or during the formation of the Chalk. We hope to 

 enter more fully into this question on another occasion. It may, 

 however, he mentioned that this is the third locality within the area 

 of the London Basin where we have noticed the incoming of higher 

 beds of the Upper Chalk, as outliers, beneath the Eocene strata to 

 be heralded or accompanied by a marked increase in the inclina- 

 tion of the bedding-planes of the former rock. 



The Winterbourne-Boxford phosphates have a known range in 

 time considerably greater than those of Taplow. Their advent far 

 down in the Micr aster cor-anguinum-Zone is especially interesting, 

 for in England, as Mr. Jukes-Browne has remarked, that subdivision 

 of the Chalk almost everywhere 



' presents the appearance of having been quietly and continuously accumulated 

 in water that was seldom disturbed by bottom-currents ' 1 ; 



albeit a tendency to develop hard bands at one horizon, at least, is 

 apparent in the western part of the London Basin. 



It is difficult to find a satisfactory explanation of the persistence, 

 or frequent recurrence, of the exceptional conditions responsible for 

 the formation of such deposits, at one spot on the floor of the 

 Senonian Sea, throughout an epoch which seems to have been no 

 inconsiderable fraction of Cretaceous time. 



The Phosphatic Chalks of Winterbourne and Taplow evidently 

 mark places on the sea-bottom particularly liable to the impinge- 

 ment of strong currents, and may mark places above which the 

 water commonly had a gyratory motion, as in an eddy. In any 

 case, their zonal range argues a marked degree of stability in the 

 current-system of the body of water in which they were laid 

 down. 



In concluding, we desire to express our thanks to Mr. George 

 Baylis, who has kindly given us access to his land around Wyfield 

 Manor ; and also to the Misses Baylis, to Messrs. Erank Comyns, 

 M.A., H. A. Allen, W. D. Lang, M.A., R. Bullen Newton, and 

 Herbert L. Hawkins, who have assisted us in various ways. 



Discussion. 



Mr. Strahax congratulated the Authors upon their discovery of 

 another occurrence of Phosphatic Chalk, and expressed his high 

 appreciation of the precise zonal work which they had carried out 

 in their investigation of the deposit. The results that they had 

 obtained could have been got in no other way. They had proved that 

 the phosphatic deposits had a greater vertical range than at Taplow; 

 they had confirmed their conclusion that the phosphatization 

 accompanied an abnormal condition of some of the zones; and 

 they had proved the existence of pre-Eocene flexures in the Chalk 



1 Mem. Geol. Surv. ' The Cretaceous Eocks of Britain ' vol. iii (1904) p. 368. 



