IN THE ANGLO-PARIS BASIN 69 



(i) HAMPSHIRE BASIN 



(a) Winchester District 



The only borings through the Gault which have yielded information of zonal value 

 are situated in the Winchester area and were drilled for the Gas Council by the British 

 Petroleum Co. 



Winchester No. i Chilcomb, Hants. (SU 50172830) 



The division between the Upper Greensand and Gault is taken at a depth of 

 310 feet (94.48 m.) and the Gault is 250 feet (76-2 m.) thick. Coring was not con- 

 tinuous and neither the thickness of Upper Albian sediments nor the exact Subzonal 

 boundaries in the Middle Albian sediments could be determined. Nonetheless, the 

 fragments of core show that between 426 feet 6 inches and 438 feet (128-16 m.- 

 133-50 m.) the essentially dark-grey silty and shelly micaceous clays contain 

 Inoceramus sulcatus indicating a lower Upper Albian age (cristatum or orbignyi Sub- 

 zones). There is then a gap of 41 feet (12-49 m -) m cored samples. 



At 479 feet (146 m.) depth, the mid-grey shelly silty micaceous clays are of Middle 

 Albian, intermedins Subzone age, and the sequence contains Anahoplites of the 

 intermedins group to a depth of 490 feet 2 inches (149-40 m.), a level 69 feet 10 inches 

 (21-28 m.) above the base of the Gault. The spathi Subzone with crushed Hopiites 

 (H.) spp. is certainly present at a depth of 501 feet 1 inch (152-73 m.), and the sedi- 

 ments from this level to a depth of at least 513 feet 3 inches (156-43 m.) consist of 

 alternating fawn and mid-grey, silty micaceous shelly clay bands. At 521 feet 

 (158-80 m.) the nacreous shells are found to be completely replaced by pyritic films, 

 and this pyritic facies is a feature of the sequence down to the base of the Gault at 

 560 feet (160-68 m.). Crushed Hopiites (H.) spp., are present in the predominantly 

 fawn-grey silty micaceous clay of the lower part of the Gault to a depth of 526 feet 

 (160-32 m.) but no ammonites have been found in the remaining 34 feet (10-36 m.). 

 The basal 5 feet (1-52 m.) of the Gault is very pebbly, becoming a pebbly loam at 

 559 feet (170-38 m.) depth. The Lower greensand underlies the Gault. 



Winchester No. 4 Itchen Valley, Hants. (SU 51133001) 



This boring produced only poor chip and core returns during its traverse of the 

 Gault. Hopiites (H.) sp. with dentatus ribbing was found at 11 feet 6 inches (3-50 m.) 

 above the base of the Gault, at a depth of 1258 feet 6 inches (383-43 m.). This was 

 preserved in an identical manner and lithology to that seen at the same level in 

 Winchester No. 1. 



Winchester No. 5 Twyford, Hants. (SU 50252712) 



Only a few cored samples were recovered from the chipped sequence. At a depth 

 of 963 feet 8 inches (293-52 m.) only 7 feet 4 inches (2-235 m -) above the base of the 

 Gault, a crushed heteromorph ammonite with indications of lateral spines was found. 

 This is almost certainly a Protanisoceras (P.) and indicates the lyelli Subzone. 



