8 On the Caves Perforating Marble 



of Mount Pilot, 6020 feet ; to the east tower the serrated 

 rocky ridges of the Cobboras mountains, 6025 feet ; while 

 intervening and winding amid bold, wooded ranges lies the 

 gorge formed by the Limestone Creek valley. Along the 

 course of the stream are a series of richly grassed open flats, 

 backed in many places by low bluffy spurs, giving in their 

 undulating contour and other appearances unmistakable 

 evidences of calcareous deposits in situ. 



Geological Structure. 



The eastern watershed (with the exception of the locality 

 hereinafter mentioned as Stony Creek) is composed of 

 masses of porphyries, fragmental and compact, the former 

 from grains as fine as sand to blocks weighing many tons ; 

 while the western watershed is made up principally of 

 slates, and interbedded bands of whitish marble and dense 

 blue limestone. The slates merging on the western water- 

 shed line into a class of schistose rocks, bearing a strong 

 resemblance to the metamorphic schists of the Omeo 

 District.* Although the Limestone Creek may generally be 

 said to have eroded its course along the contact of the 

 sedimentary rocks with the porphyries, yet the latter, in 

 the lower part of the stream, have been cut through, leaving 

 precipitous banks on either side. 



In order that the stratigraphical relation of the porphy- 

 ries to the sedimentary rocks may be better understood, 

 the following sectional notes and diagrams are given. The 

 section was determined from personal observation, and 

 crosses the Limestone Creek valley at right angles to the 

 course of the stream. 



Starting from the level of Marengo Creek (an eastern 

 affluent of the Mitta Mitta), and proceeding easterly, we 

 have, first, a mass of granitiform rock exposed on the bed 

 of Marengo Creek ; ascending . Mount Pendergast coarse 

 metamorphic schists, gneissic in character, are seen, showing 

 apparently a vertical dip. As the crest of the range is 

 reached these rocks become more micaceous, full of thin 

 quartz seams, and corrugated along the line of strike, which 

 is here seen to be N. 20' W. Descending towards the Lime- 

 stone Creek some upland alluvial flats are passed over, with 



* " The Diorites and Granites of Swift's Creek, and Their Contact Zones. 

 By A. "W. Howitt, F.G.S. Royal Society of Victoria, pp. 9 to 15. 



