rJY W. N. BKKSOX. 343 



Small intrusions of rather vesicular spilite occur at the south- 

 western corner of Portion 48, but the next important mass of 

 spilitic rock is the complex series of intrusions which runs 

 through the western ends of Portions 39, 38, and 62, and are 

 associated with serpentine in a complex fashion. The spilite 

 occurs in a series of overlapping lenticles, decreasing in size 

 from north to south; the rock is vesicular, full of secondary 

 chert, in most irregular strings and veinlets {cf. 5, p. 127). These 

 lenticles are separated from one another by narrow zones of more 

 or less silicified, crushed chert, into which the serpentine has 

 been injected. In one instance, on the northern erid of the 

 complex, the serpentine appears to be injected into the spilite 

 (though the abundance of drifted blocks makes the observation 

 uncertain), while at the southern end a small patch of vesicular 

 keratophyre, 10 yards long and o yards wide, has apparently 

 been caught up and included in the ultrabasic rock. The whole 

 structure seems to have resulted from the shattering of a mass 

 of spilite and keratophyre, by a series of oblique faults, into 

 which the cherty crush-breccias were dragged and the ultrabasic 

 rock injected. 



South of these are the long, undisturbed, lenticular intrusions 

 of dense spilite on the western slopes of Wallaby Mountain, and 

 crossing the creek at its base. These are quite typical of the 

 non-vesicular spilites in the Eastern Series. 



The keratophyres of the Transitional Zone are tirst seen in the 

 eastern end of Portions 53 and 54, and occur again on the 

 boundary of Portions 53 and 52. (A small mass of Nemingha 

 limestone lies just west of this last). In the first of these, they 

 are vesicular with amygdules filled with quartz, chalcedony, 

 chlorite, and calcite. They become abundant, however, in the 

 Water-Reserve between Portions 51 and 52, are vesicular with 

 abundant quartz in the amygdules, and microscopic examination 

 shows the abundance of quartz in the groundmass. To the 

 south, the mass of keratophyre broadens out into the largest 

 area of igneous rock within the limits of the map. Though only 

 about two hundred yards wide at the northern end of Portion 

 35, it becomes half a mile in width to the south, and continues 



