28 MIDDLE ALBIAN STRATIGRAPHY 



chambers of ammonites 3 (iii) occurs, and may be correlated with 3 (iv) at Greatness. 

 3 (iii) at Dunton Green has yielded the coarse form of A . praecox figured by Spath 

 (1925 ; 132, text-fig. 35e) according to its preservation. Only a foot of Division 4 

 was seen clear by the writer, and for the remainder of the sequence Wright's account 

 is available. 



(d) Brasted 



The Metropolitan Water Board well at Brasted has been described by Casey 

 (1954a ; 266 : 1961a ; 544-5) and is displayed in text-fig. 11. Its relationship to the 

 sections at Dunton Green and Squerryes is shown in text-fig. 3. The sequence in the 

 higher part of the well is similar to that of Dunton Green and Greatness. Un- 

 fortunately, the top of the Lower Gault bisects the ground surface further to the north 

 of the site of the well, and the boring commenced at an unknown depth below the 

 base of the Upper Gault. 



At a depth of 12 feet 6 inches (3-81 m.) the reddish burrowed marl suggests a 

 correlation with the base of 5 (i) at Greatness. The only two ammonites preserved 

 in the collection of the Institute of Geological Sciences (GSM) are Ca 339, Euhoplites 

 sp. from a depth of about 8 feet (2-438 m.), of either subdelaruei or meandrinus Sub- 

 zone age, in the preservation typical of the lower part of Division 5 at Greatness. The 

 other, Ca 340 from a depth of 10 feet (3-048 m.), is of no diagnostic value. Together 

 they neither confirm nor deny a subdelaruei Subzone age. The dividing line between 

 Divisions 4 and 3 occurs between a depth of about 22 feet and 25 feet (6-706-7-62 m.) 

 where the lithological change from fawn-grey clay to mid-grey clay occurs. The 

 equivalent of 3 (iii) at Dunton Green occurs at a depth of 29 feet (8-839 m -) an d 

 yielded Anahopiites praecox (GSM Ca 364-6) and Hoplites (H.) sp. (GSM Ca 367). At 

 a height of 1 foot 6 inches (0-457 m -) above Division 2 a phosphatised fragment of a 

 coarsely ribbed Anahopiites with the nacreous shell preserved was recovered. 



Division 2, the ' upper dentatus-spathi nodule bed ' was struck at a depth of 38 feet 

 6 inches (9-296 m.). Below this level the sequence departs markedly from that of 

 Dunton Green and Greatness. The 20 feet 6 inches (6-248 m.) of mid-grey clay below 

 Division 2 contains Hoplites (H.) spp. throughout. No definite indication of the 

 lyelli Subzone is seen, but a boring encompasses only a very small lateral area and the 

 possibility that part of this succession is of lyelli Subzone age should not be dis- 

 counted. There was also no evidence of the eodentatus Subzone although this may 

 be present below 59 feet (17-983 m.) depth. 



(v) BRASTED TO BUCKLAND 



(a) Westerham 



The northern face of the Squerryes Estate Sand pit situated 2\ miles SW. of the 

 Brasted Well was cut back in 1964 and provided the section given in text-fig. 12. The 

 sequence of well-marked lithological divisions seen in the lower part of the Lower 

 Gault in the Sevenoaks area, already indistinct at Brasted, becomes even less dis- 

 tinct at Squerryes. Here, two clear-cut divisions are immediately apparent and 



