LOWER CHALK —SOUTH WILTSHIRE. 
147 
From the line of fault near Mere the boundary of the Lower 
Chalk runs northward to the hill called the Long Knoll, near Maiden 
Bradley; passing round this, it comes within the influence of 
Warminster uplift, and runs eastward to Longbridge Deverill and 
Heytesbury. Thence with a northerly dip it passes to Warminster 
and Cley Hill; curving round this it trends north-eastward to 
AVestbury, and thence eastward in a fine escarpment above the 
villages of Bratton, Edington, Earl Stoke, and Cheverell to Market 
Lavington. 
With respect to thickness, near Shaftesbury and Berwick St. 
John it appears to be about 180 feet, but on the north side of the 
Vale of Wardour it is probably about 200 feet, and near Warminster 
it appears to be nearly 250 feet, a greater thickness than it attains 
in any other part of England. 
In the Yale of Wardour the zone of Ammonites varians has 
a considerable thickness, probably over 100 feet, but as there 
is no continuous section through the Lower Chalk, we cannot 
say how far up its fauna extends. 
The zone of Holaster subglobosus is probably from 80 to 90 feet 
thick, but that fossil seldom occurs in this district, while Am. 
[Haploceras] Austeni is not uncommon in this massive part of the 
Lower Chalk and might be regarded as locally an index-fossil to the 
zone. 
The thin band of grey marl, occasionally containing Actinocamax 
plenus , occupies its usual position. 
) Stratigraphical Details. 
Zone of Ammonites varians. 
t Q 
Basement Beds —The base of the Chalk is seldom exposed in this 
district, and its junction with the underlying sands has only been 
seen at one or two distant points. One of these is in a small pit 
south-west of the village of Charlton, near Shaftesbury ; this was 
visited by Mr. Rhodes in 1894, and he reported the section as a poor 
one, showing a little Chalk Marl, passing down into glauconitic 
marl, with marly glauconitic sand below. The succession is appa¬ 
rently similar to that in the quarry north of Melbury Hill, which is 
less than two miles distant (see p. 104). The glauconitic marl con¬ 
tains a few phosphates and some of the usual fossils, Am. [Schl.] 
varians, Scaphites cequalis, etc., and from the glauconitic sand Mr. 
Rhodes obtained Pecten asper, Lima (new sp.) Exogyra plicata, and 
Catopygus columbarius. 
I did not find any exposure of the Chloritic Marl along the south 
side of the Yale of Wardour, east of White Sheet Hill, and the only 
good exposure of it on the north side of the Yale is in the roadway 
through the wood at Knoyle Corner, about a mile east of East 
Knoyle. The beds here seen are : — 
4219 . 
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