BY G. D. OSBORNE. 523 



It is to be noted tliat, in the area under discussion, the faults are, with one 

 small exception, of the normal type, in the generally accepted use of that term. 

 The magnitude of the faults and the exposures of the rock are such that very 

 little data as to the disposition of the fault surfaces could be obtained. The 

 larger faults will therefore be considered as possessing a small hade, and the 

 amount of throw from place to place referred to in general terms. Where, 

 locally, sutHeient data are available, the stratigraphical displacement has been 

 calculated, this term being defined as the displacement of any datum point or 

 stratum at right angles to the plane of the bedding. Although the evidence points 

 to dominant- vertical dislodgment. there has been, as in the ease of almost every 

 fault, actual differential lateral movement of the earth blocks. 



Detailed Account of the Faults. 



Fault Fi Fi. — This fault is of most interest throughout the area and is first 

 made apparent by the disposition of the members of the Volcanic Stage just 

 south of Martin's Creek Station. The hypersthene-pitchstone and hornblende- 

 andesite are trimeated and placed against the quartz-keratophyre and con- 

 glomerate which overlie them by a considerable amount. Almost any of the 

 lavas in the Volcanic Stage can be used to indicate the displacement but the 

 hornblende-andesite is most instructive. The strike of this unit from Martin's 

 Creek to the fault line is N. 12° W. with a sli£ht easterly drag near the fault, 

 but the opposite edge of the lava (displaced to the north) strikes due east, cjuickly 

 changing towards the south. This type of change is illustrated by the beds ad- 

 jacent to the fault at almost any point along it. Then, at the point where the 

 fault crosses the Paterson toscanite (see map) there 's practically no horizontal 

 displacement shown, but the behaviour of the strike of the rocks nearby points to 

 dislocation, and the fault is not a pivotal one as the necessary results on the 

 south of the Paterson lava do not occur. 



The explanation of this peculiar set of outeroiDs is to be found by consider- 

 ing the structure of the fold here. A pitching anticline is present, ii-regularly 

 domed, and of the nature of a bulge with a definite steepening in one particular 

 portion, so that the two dislocated .units of toscanite have appeared adjacent, 

 subsequent to the faulting and denudation. 



The fault line has not a constant direction and the approximate throw in- 

 creases from 500 feet near Paterson to about 1,500 feet in the neighbom-hood of 

 Mt. Douglas, the downthrow side being to the east. Beyond this locality the 

 ultimate behaviour of the fault cannot be determined owing to the absence of 

 indicator horizons to delineate the structure. 



Fault F2 F2. — This fault occurs to the east of Martin's Creek and has a 

 marked effect on the disposition of the lava flows and the resultmg topography. 

 The truncation of the southerly dipping keratophyre and Mt. Gilmore toscanite 

 and the placing of the latter against the hornblende-andesite near portion 99, 

 Parish of Barford, are the most striking evidences of this fault. In a creek to 

 the north of Red Hill, along the line assumed for the fault, beds of the Glacial 

 Stage, whose normal dip nearby is 20° to the south, have a dip of 55° in an 

 easterly dii-eetion. This fault which throws to the east has a fairly constant 

 throw of about 850 feet in the northern portion of the area, but its effects in 

 the Dunn's Creek locality are difftcult to determine. It is clear that it has helped 

 to produce the complications in the structure at the head of that stream. The 

 Dunn's Creek area may be described briefly here. The syncline is very marked, 

 its existence being established by numerous dips. The axis of plunging is S. 30° 



