DEPOSITS OE THE SUSSEX COAST. 



315 



second edition of Dixon's ' Geology of Sussex,' which appeared in 

 1878, showed the same confusion between the ordinary alluvial 

 deposits and the much older ' mud-deposit ' of Selsey, some of the 

 notes evidently referring to the one, some to the other. 



In 1855 Godwin-Austen^ divided the gravels near Chichester in- 

 to an older or ' red-gravel ' and a newer or ' white-gravel ' series. I 

 can find no evidence in favour of this classification, for the red gravel 

 of that district is merely the decalcified and oxidized representative 

 of the white and chalky Coombe Eock. Sometimes, however, 

 through the long-continued action of percolating water, a still 

 further change has taken place, and the red gravel is bleached in its 

 upper part into a white gravel. The absence of fossils in the red 

 gravel, mentioned by Godwin-Austen as additional evidence for its 

 distinction from the white gravel, is a usual and necessary result of 

 the decalcifying process. The " diagram-section showing the general 

 relations of the newer Tertiary deposits of the Sussex Levels," 

 given by Godwin-Austen, does not agree in the order of the deposits 

 with any sections that I have been able to examine. This paper 

 gave, however, a number of details which added largely to our 

 knowledge of the strata. Godwin-Austen recorded the occurrence 

 of a colony of gigantic Pholas crispata in crypts in the Bracklesham 

 Beds ; he noticed also that inside the P7ioZ«s-shells were found 

 some of the characteristic southern shells belonging to the overlying 

 mud-deposit ; and he revised the list of fossils from the mud-deposit, 

 rejecting several species of doubtful origin included in the list by 

 Dixon. Godwin- Austen discussed also the climatic and other con- 

 ditions indicated by the molluscan fauna, and, on the ground of the 

 occurrence in each of Elephas primigenius, he correlated with the 

 Selsey deposit various subaerial accumulations found in other parts 

 of Sussex. This correlation is unsafe, for we now know that the 

 Mammoth had a considerable range in time. 



Above the mud-deposit came ' yellow drift clay ' containing chalk, 

 and also littoral shells ; but here Godwin -Austen appears to have 

 confounded two or more distinct strata, the yellow chalky and stony 

 clay which is the equivalent of the Coombe Eock, and the stony 

 clayey gravels with marine shells and erratics, belonging in reality 

 to the mud-deposit, or to still older strata. At the base of the 

 brick-earth one occasionally finds broken shells and masses of the 

 Pholas-hoied chalk, derived fron^D' an older marine deposit, and this 

 probably has tended to support a mistaken correlation. 



Godwin-Austen attempted to trace the various erratics to their 

 respective sources ; but he recorded only the hard rocks, such as are 

 found loose on the shore, or re-deposited in the mud-deposit. He 

 apparently did not see the softer masses from Sussex and the Isle of 

 Wight, which are so abundant in the true boulder-gravel. Though 

 I cannot speak positively on the point, it seems probable that the 

 succession given in Godwin-Austen's diagram- section^ is not alto- 

 gether accurate, and that the erratic deposit d is really the same as 



^ Quart. Journ. Geol. Soc. vol. xiii. (1857) p. 40. 

 2 Ibid. p. 49, fig. 4. 



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