26 



AUSTEALASIAN ANTARCTIC EXPEDITION. 



The bands are not uniformly spaced across the area. They may be 50yds. or 100yds. 

 apart, or they may be separated by only a foot. Three bands close together can be seen 

 on the valley floor in Plate XXII., fig. 1. In one case two bands appear to unite, but 

 the surface rock is disturbed and the junction so fractured by frost that the observation 

 is a little indefinite. A single band, however, may run out into a series of parallel threads 

 which enclose layers of gneiss between them, and these threads may unite. Detached 

 fragments of the black rock are sometimes observed to be completely enclosed in the 

 gneiss. Such fragments are either in close proximity to a band or else replace the band 

 in a discontinuous outcrop (fig. 2). These schlieren always possess a lenticular outline. 



'qratnoalioril-e 



arnphlb-oltf'e 



Fig. 2. 



DIAGRAMMATIC SKETCH SHOWING A LENTICULAR 

 "INCLUSION" OF AMPHIBOLITE LYING CLOSE TO 

 AND PARALLEL TO THE MAIN DYKE CHANNEL. 



In one example that was noted in both plan and section (fig. 3) the foliation of the gneiss 

 is bent around it, i.e., the foliation does not continue through both black and grey rocks 

 indiscriminately, though the black rock is schistose itself. This example was about 

 6ft. long and about l^ft. in diameter. These schlieren may be penetrated by quartz 

 felspar veins. 



The black rock is generally softer than the enclosing gneiss and yields more readily 

 to the mechanical weathering. Consequently the bands frequently travel along slight 

 depressions. In Plate XXII., fig. 1, where we have several bands close together, we find 

 them on a valley floor. We often find that a band forms a gully-way. The reverse, 

 however, is true in the case of a band which passes the memorial cross on Azimuth Hill. 

 Here the band has been more resistant than the granodiorite gneiss and stands as a thin 

 wall 3ft. above the level of the gneiss (Plate XVI., fig. 1). The latter is a fine-grained 

 type and contains more mica than usual. 



