Thomson'. — G'color/ij of Middle Clarence and U re Valleys. 345 



Tertiarv sandstones, and there are probably other beds of a similar nature 

 as yet undiscovered in other parts of the area embraced by the outcrop 

 of the conglomerate. There are also a small number of blocks of Tertiar)- 

 sandstone in the upper part of the " grey marls " in the Mead and Dee 

 Gorges. 



Park (1910), who examined only the exposures of the Kekerangu River 

 and Deadman's Hill, concluded that the conglomerate was a glacial moraine 

 of Pleistocene (early Notopleistocene) age. This hypothesis involves the 

 formation of the great Clarence and other faults in the late Notopleistocene, 

 and is quite untenable. In any case, the evidence for the fluviatile origin 

 of the lower beds of the series is overwhelming. 



Cotton (1914) agrees with Hector and McKay that tlie conglomerate 

 as developed in the Middle Clarence Valley is of fluviatile origin, but 

 considers it not necessarily the work of a single river. The line of out- 

 crop thirty miles in length indicates that it was there deposited as a 

 piedmont alluvial plain and not as isolated fans. The evidences of fluviatile 

 origin are chiefly the rough sorting of the material into coarser and finer 

 bands, and the presence of fine regular sandstone bands, often lenticular, 

 coupled with an absence of distinct false bedding or an arrangement of 

 foreset beds that would indicate beach or delta conditions of subaqueous 

 deposition. The character of the conglomerate presents striking analogies 

 with the terrestrial deposits in Owen's Valley, California, and satisfies most 

 of the criteria drawn from the study of alluvial and fan deposits. 



As has already been stated in the general account of the geology and 

 ])hysiography. Cotton accounts for the peculiar features of the conglomerate 

 — viz.. that it lies conformably on the '" grey marls " but contains materials 

 of all the underlying Notocene beds — by assuming that a neighbouring area 

 was dift'erentially elevated to the extent of perhaps as much as 12,000 ft. 

 without seriously disturbing the horizontal altitude of that portion of the 

 Notocene series which, a little later, had the conglomerate deposited upon it. 

 Since folding and war ping seem to be out of the question, as the surface 

 of the " grev maris "" is not appreciably tilted, he concluded that the 

 differential movement must have been block-faulting, with the restriction 

 that the uplifted block alone moved. The presence of small normal faults 

 dislocating the conglomerate and '" grey marls " is held to be significant 

 in this connection, since block-faulting usually takes place along normal 

 faults, and for a long period after the main faulting the formation of small 

 normal faults continues, dislocating the fan deposits resulting from the 

 erosion of the earlier fault-scarp. (L'otton, it should be noted, confined his 

 explanation solely to the conglomerate as developed in the Mead and Dee 

 Gorges. Whether it is equally applicable to all other exposures of the 

 conglomerate cannot be decided without a much more intensive study 

 of these exposures than has yet been made, but its frequent if not 

 invariable association with the " grey marls " is significant. 



In all the exposures in the Clarence Valley, and in the majority 

 elsewhere, the conglomerate rests on a surface of the " grey marls." The 

 chief exceptions, as described by McKay, are at Greenhills (south of the 

 Looker-on Range), in the Kekerangu River, and in the hills between Ward 

 and Lake Grassmere. At Greenhills McKay's section (1886, p. 81) shows 

 it resting, apparently conformably, on the Amuri limestone, but he states 

 that '■ somewhat obscurely conglomerates are seen on the east side of the 

 saddle mentioned, and it is at the same time quite apparent that the 

 . limestone could not terminate in the manner it does without being suddenly 



