30 GEOLOGICAL NOTES ON KOSCIUSKO, 



It is obvious that the sedimentary rocks at Barnej^'s Ridge form 

 a basin bounded by granite on the east and on the west sides. 



From the point previously mentioned, 27 miles and 15 chains 

 on the road from Cooma to Jindabyne, the typical Kosciusko 

 granite replaces the Lower Silurian rocks, and continues, more or 

 less, without interruption to the Kosciusko Plateau. 



The Kosciusko Plateau rises abruptly from the valley of the 

 Crackenback River to an altitude of a little over 5,000 feet (about 

 5,200 feet) at Boggy Plains up to 6,000 feet at Pretty Point (top 

 of Point) and culminates at an altitude of 7,328 feet at the 

 summit of Kosciusko, where Mr. Wragge's Meteorological 

 Observatory now stands. 



The plateau is for the most part formed of gneisssic granite 

 very full of dark enclosures. These are mostly not basic 

 segregations or secretions, but fragments torn from older rocks, 

 some of them being fragments of micaceous quartzite and quartz 

 schist. The folia of the granite strike about 8.S. W. and N.N.E., 

 dipping chiefly to E.S.E. at varying angles, perhaps 70° being 

 near the average. 



The granite is traversed by dykes of pyroxene-amphibolite 

 rocks, passing by decomposition into a chlorite rock. There are 

 also present whitish veins of hard aj^litic granite, which seem of 

 somewhat later origin than the mass of the granite. One of these 

 veins is shown in Plate vii 



The granite is also traversed by dykes of olivine-basalt con- 

 taining enclosures of granite. A large dyke of this kind may be 

 observed at Strzelecki's Pass (Lendenfeld), close to Russell's Tarn 

 (Helms), a short distance from Mount Townsend. Another on 

 the main dividing ridge above Garrard Tarn (Harnett's Lake), 

 and a third on the west side of Lake Mere wether (Blue Lake). 

 (Plate iii.). A very interesting dyke rock was discovered by us 

 at a point about one-quarter of a mile up Evidence Valley (Valley 

 of Blue Lake) from its junction with the Snowy River. The 

 dyke is about 7 feet wide and strikes E. 5^^' N., and is vertical. 

 It is almost entirely formed of the minerals nepheline and 



