64 
THE CRETACEOUS ROCKS OE BRITAIN. 
CHAPTER VI. 
THE LOWER CHALK IN SUSSEX. 
1. West Sussex. 
General Description. 
Sussex being a long county, and including nearly the whole of 
the South Down range, it will be convenient to divide our descrip¬ 
tion of the Lower Chalk of Sussex into two portions. We shall 
regard the western part as extending from the boundary of Hamp¬ 
shire to the valley of the Adur, a distance of about 26 miles. 
In this part of Sussex the features presented by the basset sur¬ 
face of the Lower Chalk resemble those of the same surface in Surrey, 
and differ from those of the Hampshire outcrop. In other words, 
the outcrops form a steep slope, except near the base, where the 
Chalk Marl generally runs out in a gentle slope or plain to meet 
the inward or southward slope of the Greensand terrace. 
With respect to zonal and lithological composition the Lower 
Chalk of this region may be regarded as a continuation of that of 
Hampshire. There is a similar bed of Chloritic Marl at the base, 
overlain by a certain thickness of soft grey crumbling marl which 
passes up into bluish-grey marly chalk. The upper beds consist 
of white blocky chalk crowned by a bed or beds of firm, greenish- 
grey marl (the zone of Actinocamax plenus). 
In regard to thickness, also, there seems to be little change. Mr. 
Reid informs us that he considers there is at least 180 feet of chalk 
between the basement-bed and the Belemnite marl at the top. 
Although the chalk of Sussex has yielded many fine fossils, and 
large collections were formed bv Dr. Mantell and Mr. Dixon, vet 
these collections were made before any accurate division of the 
Chalk was established. Fossils referred by them to the Chalk Marl 
may safely be included as Lower Chalk fossils, and probably most 
of them will have come from the zone of Ammonites varians , but 
the Lower Chalk of Mantell and Dixon was simply the more solid 
chalk without flints, and consequently included part of the Turonian, 
or Middle Chalk. 
Since that time few geologists have examined the Lower Chalk 
of Sussex, and the western part of the county has been quite 
neglected. We are not aware that anyone has described the zonal 
succession at any locality, and we ourselves have not had time to 
make special researches in this area. 
The whole Chalk area of Sussex was, however, re-surveyed during 
the years 1889-1891 by Mr. C. Reid, who drew the lines for 
the Chalk Rock and Melbourn Rock, but was instructed not to 
