LOWER GREENS AND. 



55 



CoMPTON Bay to Redcliff. 



At Compton Bay the Carstone is a broAvu sandstone, having as 

 its basement layer a band, three inches thick, of qnartzite pebbles, 

 ranging up to three-quarters of an inch in length, with rolled 

 phosphatic pebbles, many bits of wood, and cylindrical concretions 

 which seem to have been formed in place. Though the beds below 

 also contain pebbly bands, they appear to be more of the type of the 

 Sand-rock Series, and to be divided from the Carstone by a hard 

 and fast line. Upwards the Carstone passes gradually into the 

 Gault, the nature of the junction being shown in Fig. 7 (p. 23) 

 and in the accompanying sketch by Professor E. Forbes. 



Fig. 13. 



Junction of the Gault and Lotoer Greensand in Compton Bay. 



a. Dark blue sandy clay (Gault). 



b. Brown sand mtli a pebble-l^and, three inches thick, at the 



base, containing quartz- pebbles, raany pieces of wood, 

 and some phosphatic pebbles ^Carstone) 



c. Blue sandy clay - - - - _ - 



d. Grey and greenish sand with small quartzite'pebbles at the 



top and the bottom, and with a layer of pyritised wood, 

 4 feet from the base . . - - . 



e. Bright-yellow sand ..... 

 /. A ferruginous band, about .... 

 g. Irregularly interlaminated white sand and blue clay (for 



the continuation of this section, see p. 22). 



Ft. In. 



13 

 9 

 1 



Eastwards from Compton Bay there is no section of the Car- 

 stone, though its position can be determined with some accuracy 

 by the nature of the soil. In the section of the Sand-rock Series 

 at Eock (p. 41) the base of the Carstone is exposed, but no 



more. 



There are indications, however, of the steady thickening of this 

 subdivision eastwards. Not only does the outcrop widen, but 

 south of Coombe Tower the rock begins to form a distinct escarp- 

 ment, which gradually becomes the best marked feature in the 

 Lower Greensand. Wherever exposed the rock consists of a brown 

 and ferruginous grit. 



