Vol. 52.] 



A DELIMITATION OF THE CENOMANIAHT. 



117 



Gault. 



The Gault and Upper Green sand — The Albien of 

 M. de Lapparent. 



Above the coarse pebbly grit comes a dark, sandy, glauconitic 

 clay, almost black when wet, which passes up into a sandy 

 and glauconitic marl. This is the equivalent of our Gault and 

 Greensand, the Gault and Gaize of French geologists ; there is no 

 plane of division between them, the one grad daily passing up into the 

 other. 



The lower part of this division can be conveniently seen near 

 Ste. Adresse, \ mile south-west of the lighthouses, where the fol- 

 lowing section was taken, in descending order : — 



( Dark bluish-grey, sandy, micaceous, and glauconitic 



clay, seen for 7 feet. 



Dark bluish-grey (almost black), sandy, and very glau- 

 conitic clay, containing a few light-coloured phos- 

 phates (dark internally) 4 feet. 



Bed of phosphatic nodules, contained in a mixture of 

 the underlying coarse sand and the glauconitic 



sandy clay above 6 inches. 



Coarse, brown, sandy grit, containing pebbles as large 



as a bean 3 feet. 



Aptien. \ Coarse, brown, sandy grit 8 feet. 



j Soft greyish-yellow sand was seen below this ; the 



[_ junction-bed, however, was not attainable 15-18 feet. 



The bed of light-coloured phosphate-nodules intermingled with 

 the bed below, the nodules often including small quartz and lydian- 

 stone pebbles. 



The micaceous clay of the Gault passes up into a sandy, glauconitic, 

 micaceous, and slightly calcareous marl containing small dogger-like 

 concretions, and as one follows it upward these concretions increase 

 in importance and number, and finally divide the deposit into courses. 

 At the top of the division the doggers give place to definite beds in 

 which silica seems to saturate the deposit, forming hard courses, 

 which alternate with courses of softer marl. 



The following is a detailed section through the Gaize and Gault 

 at a point nearly 1 mile east of the lighthouses on Cape La Heve : — 



Feet. Inches. 



Chloritic Marl (see p. 119) 6 



f Alternating beds of blue-grey marl and beds of hard 



siliceous stone 3 6 



Dark blue-grey, sandy, glauconitic marl, containing 

 doggers of hard siliceous stone, arranged more or 



less in layers 7 



A double line of doggers, separated by blue-grey, 



sandy marl 1 



Blue-grey, softish, sandy marl 1 



Dark blue-grey marl, with a line of large and well- 

 separated doggers 1 



Dark blue-grey marl, with small scattered doggers, 



^ arranged more or less in lines 11 



I Very dark, almost black, marly, glauconitic clay ; a 



\ layer of phosphatic nodules at the base 10 



f Coarse pebbly brown sand 16 



\ Yellow micaceous sand 70 



k2 



Gaize 



or 

 Upper 



Greensand. 



Gault. 

 Aptien. 



