Mocks of tlte Horvqua River. 55 



On the western side only Upper Ordovician and, possibly, Silu- 

 rian graptolites^ have been noted, and these come from a very 

 restricted area. Slaty rocks often somewhat talcose and chloritic 

 prevail, sandstones and quartzites being subordinate. The rocks, 

 are frequently intensely contorted, particularly at the '* Gover- 

 nor," and a long line to the north west of this. 



The unweathered slates were often black, as at the outcrop below 

 the pack-horse bridge at Fry's. By oxidation and leaching, how- 

 ever, they are often almost white. 



They only show slight local chertification, and no Frotospongia 

 has been noted in these cherts. 



On the eastern side, however, the black Protospongia cherts are- 

 well developed, forming a continuous belt up to half a mile ia 

 width, directly in contact with the diabase. Ihese cherts stop 

 suddenly to the east and give place to a dark, micaceous and 

 slightly felspathic sandstone, which appears to be quite conformable 

 and then follows a thick succession of olive green phyllitic slates,, 

 alternating with sandstone and quartzite. Traversing these rocks 

 across the strike in a north-easterly direction tow^ards Mount- 

 Buller, at about one and a-half miles from, the cherts, thin black 

 slate bands begin to occur interbedded with the olive green slates 

 and sandstone. Two of these bands have yielded Tetragraptus and 

 D.idymograjjtus, thus indicating a Lower Ordovician horizon. 

 Continuing still further to the north-east, and approaching the 

 Mount Buller grano-diorite, these sediments give place to belt of 

 dark cherty slates, and fine grained quartzite, often veined with, 

 quartz. Microscopic sections of these rocks indicate contact 

 phenomena attributable to the proximity of the plutonic intrusion. 

 These indurated rocks form a very jagged outcrop, to which the 

 rough outline of Little Buller is due. 



Following up the valley of the Howqua, the direction is in 

 general easterly, and, therefore, crosses the strike of the same- 

 series of sediments in an oblique direction. The Lower Ordovician 

 strata, yielding Tttragraptu^ and Bidymograpfus, have not been 

 noted, but at a few chains west of Eight Mile Creek, indistinct 

 graptolites were found in black cherts. These were too poorly pre- 

 served for certain identification, but they suggested D'jilograptvs 



1. The writer has spent days searching alongr the restricted area where Mr. 

 A. M. Howitt obtained a graptolite, identified by Dr. T. S. Hall as a 

 Monograptvs, but did not find a single specimen of this genus, though 

 hundreds of specimens of less restricted range were obtained, chietly 

 CUmacograpfus and Diploorat)tus, with probably Glossograptus and other 

 doubtful forms. 



