THE GREAT MARLBOROUGH CONGLOMERATE 361 



the angle of hade is in no case great and the faults are all normal. 

 There are, therefore, good grounds for the assumption that the 

 faults were formed while the beds still lay in their original position. 



One fault on the southwest side of the Dee gorge, which may 

 be taken as an example, is illustrated in Fig. 7a. The line of fault, 

 in the section exposed, slopes down to the east-southeast and makes 

 an angle of 75° with the vertical, and a sandstone band in the con- 

 glomerate is displaced a distance of 4 ft. toward the east. 



In the gorge of the Mead, as noted in an earlier paragraph, the 

 faults are numerous, the fault planes striking about east and west. 

 Fig. 7& is a sketch of one 

 of them in the conglom- 

 erate gorge, which has a 

 downthrow of i ft. 6 ins. 

 to the south, and others ese *^^ 

 are shown in Fig. 4. Very 

 numerous faults can be 



seen in the Mead gorge 



, ,, 1 ,1 Fig. 7. — Faults in the Great Marlborough 



passmg down through the conglomerate. 



Grey Marl into the Amuri 



Limestone, but owing to the nature of these strata, the faults are 



less conspicuous in them than in the conglomerate. 



GEOLOGICAL HISTORY 



During a long period extending from some time in the Cre- 

 taceous to well on in the Tertiary, deposition had been going on in 

 the Middle Clarence Valley area under geosynclinal conditions, that 

 is, upon a sea floor that sank gradually during the greater part of 

 the period. Toward the end of the period of deposition of the 

 Amuri Limestone subsidence ceased, and the character of the 

 deposits became more and more argillaceous as the water shallowed. 

 There is thus a gradual passage from the typical Amuri Limestone 

 to the typical Grey Marl. The upper portion of the latter becomes 

 somewhat sandy and contains layers of small pebbles from the 

 old land. The presence of these does not necessarily imply uplift, 

 but slight regional uplift, if it had occurred, would have sufficed 

 to revive slightly the streams of the old land and so to increase 



