PRESIDENT S ADDRESS — SECTION C. 



109 



thrusting of th© mica-schists over " Early Tertiary " conglomerat-es 

 in two localities in Eastern Otago. The fault planes dip at angles 

 of 25 dee. -35 deg., and one broad aroa of slicken-side®, the Blue 

 Spur at Lawrence, has been swept clear of the overlying gravelly 

 conglomerate for an area of about 16 acres. It had formerly 

 been suggested that it was a glaciated pavement. In the Nelson 



YARDS 



Fig. 9. Section at Bob's Ctove, Lake Wakatlpu. (After Park, 1909.) 

 (a) "Miocene" sandstone and conglomeiate. (b) "Miocene" Limestone, 

 (c) " Miocene " Marly sandstone, (a) " Miocene " Marly clay, (e) " Miocene" 

 Calcaieous brescia-conglomerate. m«. Mesozoic ? mica-sctiist. 



district, the Cainozcic rocks are overturned adjacent to the fault 

 bounding the older rocks, and, alternatively to the older inter- 

 pretation, the writer would suggest that the Brook-street volcanic 

 rocks have been thrust O'ver the inverted Tertiary coal measures* 

 (See Figure 1.) An interesting example of very late lateral move- 

 ment is de?cribed by Morgan (1908) ,* where schists have been thrust 

 over Recent rivrr-alluvium. In Westland, the evidence of lateral 

 movement does not seem to be so great as in the regions described 

 above. Henderson (1917) summarizes the history of deformation 

 here as follows: — Four periods of faulting occurred during Caino- 

 zoic times, viz., prior to the " Eocene," prior to the " Miocene." 

 between " Miocene " and " Pliocene " and post-" Pliocene." The 

 faults present the usual characteristics. The movement, even 

 along the same dislocation, may be concentrated in a single fracture 

 with walls close together, or perhaps several chains apart, the 

 intervening space being filled with comminuted rock. Again the 

 fault may be a shear-zone, with numerous sub-parallel and closely 

 spaced polished surfaces, with the intervening rock rendered 

 schistose, but always more or less deformed. One type of fault 

 constantly recurs, narrow trough-faults, in which the rock between 

 the main fault-walls belongs to a higher horizon than the walls 

 themselves. When the Cainozoic beds, which overlie the Palaeozoic 

 sediments and granites, are involved, the detection of this type of 

 fault is very easy. The main fracture-planes nowhere appear to 

 deviate far from the vertical. 



* Dr. Marshall, in conversation, remarked that he has already formed this opinion. 



