60 Notes on the Geology of the Country around Goulburn. 



the counties of Argyle and King. But in the south half of the 

 county the arm of the dividing range, bounding the drainage 

 area of Lake George on the east is coloured yellow, being com- 

 posed of stratified rocks ; whilst the arm on the west consists of 

 granite. A little to the north of Mount Cullarin basalt com- 

 mences, and forms the rest of the northerly curving continuation 

 of the range bordering the north-west of the county. The map 

 represents the Wollondilly flowing along a granitic course from 

 its origin to a point about nine miles west of Groulburn, and this 

 granite continues in a strip southwards, as far as the Lake 

 "Wologorong and Eose Lagoon (Lake Tarago on the map). 

 Basalt encircles the valley of the Wollondilly in the early part 

 of its course. 



The priDcipal features in the eastern border of the yellow 

 central band consist, first, of an area of quartz porphyry, indi- 

 cated by the buff colour, which covers an extensive tract about 

 Marulan, stretching from the Wollondilly to within a short dis- 

 tance of the Shoalhaven, and thence tapering south for a distance 

 of eighteen miles ; secondly, of the black area, lying on the east 

 of the former, indicating some interesting outliers of conglom- 

 erate and sandstone belonging to the coal formation. Limestone 

 is occasionally found interbedded with the metamorphosed arena- 

 ceous and argillaceous strata ; it is shown by the blue colour, 

 but it forms a very inconspicuous feature in comparison with the 

 other rocks. Isolated patches of granite or- syenite, quartz 

 porphyry, basalt, and greenstone are met with here and there, 

 and are indicated on the map by the carmine, buff, green, and 

 brick red respectively, and help to enliven the monotony of the 

 yellow colour ; for instance, granite occurs north of Lake 

 Bathurst, a chain of basaltic patches runs in a direction N.E. 

 from the same lake ; greenstone occurs at Willeroo, in the 

 neighbourhood of Lake Greorge, and also on King's Plains, near 

 Goulburn. 



Taking into consideration the small scale of the map (two 

 miles to an inch), and the difficulty of ascertaining the nature of 

 the bed rock in many places where the covering of soil is deep, 

 the colours will afford a rough approximation of the size and 

 s!iape of the areas occupied by the various formations. 



Reckoning the area of the entire country at 1600 square miles, 

 lO.sO are represented by the yellow (altered strata of clay and 

 sand); 100 by the green (basalt) ; 60 by the buff (quartz por- 

 phvry) ; 90 by the carmine (granite and syenite) ; 6 by the blue 

 (limestone) ; 14 by the black (conglomerate belonging to the 

 coal formation) ; whilst the remaining uucoloured 250 square 

 miles are unexamined. 



