UPPER EOCENE (bARTON AND UPPER BAGSHOT FORMATIONS). 581^ 



sea, as indicated by the prevalence of sharks' teeth and fish-palates 

 in it, the period ushering in the Barton must have been one of up- 

 heaval. We cannot expect to trace our base-line of sand and shingio 

 in all localities, because the same amount of upheaval taking place 

 in deeper water would merely result in a diminution of depth with, 

 perhaps, but a slight change in the character of the sediment and 

 nature of the fauna. The passage in the Isle of Wight, and pro- 

 bably in the direction of the New Eorest, between the Barton and 

 Bracklcsham Series is, in fact, an almost imperceptible one, and in 

 some places they appear a practically continuous formation. This 

 mass of sand and shingle is, at Highcliff, followed by dark green 

 sandy clay, similar to that of the Bracklesham beds, but full of 

 drifted wood, fruits, and fir-cones, and coniferous twigs, and com- 

 prising a thin band with Nummidites elegans, fish-teeth, and, more 

 rarely, bony plates of Chelonians and Crocodiles. This assemblage, 

 confined, apparently, so far as vegetation goes, to objects with 

 considerable powers of flotation, should give a great insight into 

 the conditions of deposition, were observations of the necessary 

 kind in existing estuaries not so scanty. A ferruginous band 

 marks, x)erhaps, a considerable shift when the deposition of mud 

 was almost suspended, and preceded a change which ushered in the 

 stiff drab clay of the Highcliff Beds proper. That the water still 

 remained shallow is apparent, since the shells, unless minute, are 

 broken into small fragments and drifted with sand into pockets. A 

 shore-crab, described by Dr. Woodward, was probably from a zone 

 of pinkish clay in this part of the series. A small Echinoderm is 

 abundant near the base, and first Psammohia and then Plioladomya 

 become common, and are always found in the vertical position 

 assumed by them in life. Next we have the Middle or true Barton 

 Clay, at first glauconitic and then plastic, with its rich assemblages 

 of shells, many of large size, and ending with great and wide-spread 

 drifts of shell-matter, chiefiy comminuted and in an irony matrix. 

 This is succeeded by a mass of sand crowded with Chamas and a 

 peculiar fauna, which appears for the first time and as suddenly 

 disappears, giving place to the truly estuarine Becton-Bunny Beds, 

 which in turn pass upward into the brackish Long-Mead-End Beds, 

 and then into the fluviatile Lower Headons. 



Great interest attaches to the Barton Series on account of its 

 fauna, which is both rich and, to a large extent, peculiar. Prof. 

 Prestwich long siace remarked on the more northern character of 

 its Mollusca, contrasted with those of the Brackleshams *. The 

 submergence implied by him seems, in fact, to have destroyed 

 some narrow barrier or isthmus which for a long period had kept 

 the Southern Eocene sea, of which the Brackleshams are the earliest 



* " The Barton-clay sea seems again to have been more connected with water 

 opening to the northward than did that of the Bracklesham Sands ; for several 

 species of the London-clay sea . . . that had disappeared in the intermediate 

 Bracklesham period, reappear in the Barton series. In fact, the fauna of 

 this group, together with that of the Sables Moyeus, has not so southern an 

 aspect as that of the Calcaire grossier and Brackleshani period." (Quart. Journ. 

 Geol. Soc. vol. xiii. p. 131.) 



