308 GEOLOGY AND PETROLOGi' OF THE GREAT SERPEXTIXE BELT OF N.S.W. 



felsitic magmas iu late Palaeozoic times, and by which, at the present time, the 

 structures have been rendered less resistant to stream erosion. Concerning other 

 miportant dip-faults, we may note that these have also very extensive throws. 

 The fault immediately north of Duri Peak thi-ows the andesite down nearly nine 

 hundred feet, but, though the displacement of the andesite directly to the east 

 has not been measured, it has clearly not been moved along the fault to the same 

 extent as the mass composing Duri Peak. This mass again is cut off to the south 

 by two faults with an aggregate throw of over twelve hundred feet. This, how- 

 ever, does affect the rocks to the east, but the southern side of the fault is the up- 

 throw side to almost as great an amount. Two miles further south there is an- 

 other fault, possibly a branch of the Currabubula Creek fault zone, and this has 

 moved the main zone of andesite so that the southern side of the fault has been 

 thrown up over six hundred feet. 



South of Currabubula Creek the mass of andesite in the valley of Sandy 

 Gully is brought up by a fault of at least nine hundred feet throw, which is fol- 

 lowed immediately by another of about four hundred feet throw. Both these 

 seem to affect the sedimentary rocks immediately to the west to some extent, 

 but have no noticeable effect on andesite to the east, unless the first strikes through 

 Currabulnila Creek Gap also, where a fault movement of about a hundred feet ha'! 

 occurred . The mass of andesite in the valley of Sandy Gully is again cut by 

 faults, the one throwing up to the south about four lumdred feet, and the other 

 with a throw of perhaps nine hundred feet completely cutting off the mass of an- 

 desite, but neither of these appeai-s to have had any effect on the andesite of the 

 main zone immediately to the west. This extraordinary diversity of movement 

 along the one fault line, witliout an accompanying change of dip, owing to local 

 warping, can lie best explained Ijy the presence of several strike-faults, and the 

 assumption that the region was tilted, fractured by strike and dip-faults, and the 

 blocks into which the crust was thus separated moved up and down to various ele- 

 vations. Unfortunately direct evidence of the existence of such strike-faults is 

 wanting save for that running west of Kingsmill's Peak. The occurrence of a belt 

 of mudstone beside the main zone of andesite directly east of Duri Peak, and 

 again midway between the western and main zone of andesites crossed by the 

 section line two miles to the south, may result from the presence of such strike 

 faulting (Compare Text-fig. 3a, Sections A — ^B and C — D). The sections, how- 

 ever, merely indicate that some of these strike-faults occur: their positions and 

 amount of throw .ire as yet almost entirely conjectural. 



The occurrence of dip-faults recalls the faults of the Loomberah District (261 . 

 It may be that these faults are the continuation of the same regional series per- 

 pendicv;lar to the fcild axes as are there represented. Moreover, it was shown in 

 the paper cited, that the movements along the lines both of dip- and of strike- 

 fault must have continued on into the close of the Pcrmo-Carbon- 

 iforous times, or have been then repeated as jiostliumous movement. The 

 same appears to lave been the case near Werris Creek where the Permian ( ?) 

 (rlnsxopferis sandstone has been let down anidiig the Wcirie basalts alcm^ fatiltl 

 parallel to the old strike lines. 

 The Age of the Werrie Volpaxic Serte.s and Tt.s Relatiox to the Cru.st 



M0\T5MEXTS. 



The sequence of events shown by the sedimentary and igneous record indi- 

 cates a close association between crust-movements and igneous action. An ex- 

 tensive upward warping of the crust is indicated by the gradual change in con- 



