CHALK 85 



again in 1875,* and described as occurring at about its proper 

 distance above the Chalk Rock. Presumably therefore its ir- 

 regular appearance in the Brixton pit was the result of squeezing. 

 The dip ranges from 27° to 30°. Southwards from this pit the 

 high road passes steep banks of thin-bedded chalk and marl, 

 which become very impure and sandy in the lower part, and 

 so merge into the Chloritic Marl (p. 81). 



Near Coombe Tower, north of Brixton, several large pits in 

 the Lower Chalk reach upwards into more massive beds which 

 geem to be the Middle Chalk, but the Melbourn Rock is not 

 distinguishable. 



The large pit at Shorwell exposes this rock, but unfortunately 

 in a position wherein it is quite inaccessible at present. The strata 

 consist of thin-bedded chulk and marl (Lower Chalk) but the 

 top of the vertical wall of the pit is formed of a hard flaky chalk, 

 underlain by a thin seam of marl, the appearance of the beds, 

 as studied at a distance of a few feet, being the same as that of the 

 Melbourn Rock near Arreton and Yarbridge {postca, pp. 88, 89). 



The next sections are found in the projecting promontory of 

 Chalk of Chillerton Down. The uppermost pit touches the 

 Chalk Rock, but starts a few feet below the Chalk-with-flints. 



Chillerton Down. 



r Massive chalk _ . - 



Vovev Chalk ■< ^^^^ ^^^^^ .... 

 ^' I Massive chalk ... 



L Green-coated nodule bed (Chalk Rock) 



Middle Chalk I J^"^':, ^"°fl*t ''^l\ 

 I smoother flaky chalk 



The Middle Chalk, v/hich has been worked, is now overgrown ; 

 but the Lower Chalk, presenting its usual character of thin- 

 bedded chalk and marl is worked in the lowest pit. At least 

 three faults are visible in the pit, In each case with slickensided 

 faces, coated with a film of blue marl. Two of them range 

 nearly north-east, throwing down a wedge between them, while 

 the third runs north-west with a downthrow to the south-west. 

 The dip is at 7° — 9° to the north, but decreases to 2° or 3° 

 further north towards Gatcombe, and changes in direction to north- 

 west. The faults may be connected with this change. 



The boundary of the Upper Chalk is shown upon the map, as 

 running across the Downs from near Shorwell to Carisbrook, but 

 the hills lying outside this boundary are believed to be capped 

 with outliers of Upper Chalk. The existence of outliers there is 

 not quite certain, because of the uniform sheet of flint gravel cover- 

 ing the tops of all the hills, but it is inferred from the position of 

 the Chalk Rock in the pit last described. They must, however, 

 be exceedingly thin, the Chalk-with-flints having nearly all 

 mouldered down into flint gravel. The few pits, which are open 

 round the brows of these hills, expose the massive beds of the 

 Middle Chalk. The best sections in the Lower Chalk are to be 

 found 500 yards south of Newbarn and at Garstons. 



* Description Geologique de la Craie de I'lle de Wight, p. 18. 



