GEOLOGY OF MOUNT KOSCIUSKO. 369 
which reveals signs of crushing in several of the rocks, shows 
clearly that the Kosciusko rock masses have been subjected to 
great earth stresses. Generally speaking, it seems that the oldest 
rocks were sedimentary ones of probably Ordovician age. These 
were intruded upon by granites of various kinds, which built up 
the major portion of the plateau. Subsequently numerous dykes of 
acidic and basic rocks, such as aplites, andesites, and diorites, were 
injected, and the greater part subjected to dynamic metamorphism, 
followed probably by later series of dykes. Thus the metamor- 
phism has been of two kinds—contact and dynamic—the former 
altering the original sediments into quartzites, lydianites, por- 
cellanites, &c., and the latter carrying the alteration further, and 
transmuting these into micaceous hornfels, quartz-schists, mica— 
and felspathic mica-schists, and perhaps gneiss, and the intrusive 
granite into gneissic granite and gneiss. The metamorphism, 
therefore, appears to have been similar to that which produced the 
interesting rocks found in certain portions of the Omeo and Dargo 
districts in Victoria, and described* by Mr. Howitt. 
The question of glaciation has evidently been the most potent 
factor in stimulating geological research in this region. Several 
writers are of opinion that evidences of such action exist. Unfor- 
tunately, we were unable to examine any of the localities and 
deposits described by them, as our observations did not extend so 
far northwards, so can express no opinion regarding their main con- 
clusions. In many places in the valleys we observed large masses 
of granite with polished surfaces, which at first sight appeared to 
be of glacial origin, but proved to be simply weathered joint and 
fracture planes. In other places, however, evidence of another. 
nature seems to indicate ice action. On the south-western slope of 
Mount Etheridge lie numerous large and small pieces of altered 
sedimentary rocks, and masses of red and grey aplite, and granite. 
Many of the indurated and highly altered rocks are more or less 
smoothed, polished, and widely grooved. They are of both fine and 
coarse texture, and the latter only are devoid of joint planes which 
are quite different from the smoothed faces. On its western slope, and 
also lower down on the floor of Kosciusko Valley are great numbers 
of worn stones almost exclusively of altered sedimentary origin. 
*“ Notes on the Physical Geography and Geology of North Gippsland,” Quarterly Journal 
of the Geological Society, vol. xxxv. ‘‘The Diorites and Granites of Swift’s Creek,” 
Transactions of the Royal Society of Victoria, vol. xvi. ‘‘The Rocks of Noyang,” Trans- 
actions of the Royal Society of Victoria, vol. xx. ‘‘The Sedimentary, Metamorphic and 
Igneous Rocks of Ensay,” Transactions of the Royal Society of Victoria, vol. xxii. ‘‘ Notes 
on the area of Intrusive Rocks at Dargo,” Transactions of the Royal Society of Victoria, 
vol. xxiii. ‘‘ Notes on certain Metamorphic and Plutonic Rocks at Omeo,” Transactions 
of the Royal Society of Victoria, vol. xxiv, Part ii. ‘‘ Notes on certain Plutonic and 
Metamorphic Rocks at Omeo, ’Mining Department Quarterly Report, March, 1890. ‘‘ Notes 
on the Rocks occurring between the Limestone River and Mount Leinster,’ Mining 
Department Quarterly Report, September, 1890. ‘‘ Notes on the Contact of the Meta- 
morphic and Sedimentary Formations at the Upper Dargo River,” Mining Department 
Special Report, 1892. ‘‘ Notes on the Metamorphic Rocks of the Omeo District,” Report of 
the Australasian A. A. Science, Sydney, 1888. ‘‘ Notes on the Metamorphic Rocks of Omeo,” 
Report of the Australasian A. A. Science, Melbourne, 1890. 
Wy IN 
