Art. VII. — Tlie Geology of Coimaidai. 



Part I. 



The Coimaidai Limestones and Associated Deposits. 



By GiiAHAM Officrk, B.Sc, aud Evelyn G. Hogg, M.A. 



[Read 10th June, 1897.] 



The ceolosrical interest of the district of Coimaidai arises from 

 the occurrence there of (1) magnesian limestones containing 

 mammalian bones, and of (2) glacial deposits. Some of our 

 conclusions concerning the latter beds have been already given 

 in a paper read at the last meeting of the A.A.A.S. at Brisbane. 

 In the present paper only the limestones and" other formations 

 associated with them will be dealt with. 



The area under description is situated in the parishes of 

 Merrimu and Coimaidai, County of Bourke, and lies a few miles 

 north of the town of Bacchus INlarsh ; it is included between the 

 Lerderderg River on the west and south and the Djerriwarrah 

 Creek on the east, while northwards it extends some miles 

 towards Mount BuUengarook. In addition to the two streams 

 mentioned, several creeks, flowing in a southerly direction, 

 traverse the area, exposing many good sections along their 

 courses. The principal creeks are Goodman's Creek, Boggy 

 Creek, and Pyrete Creek. It is in the valley of the latter creek, 

 in the vicinity of the township of Coimaidai, that the limestones 

 are best exposed. The area of the district is about thirty-six 

 square miles. 



The formations developed in the disti^ict are, in ascending 

 order — 



(1) Lower Silurian. 



(2) Perino-carboniferous Glacial beds. 



(3) Coimaidai limestones, gravels, conglomerates, etc. 



(4) Newer Basalt. 



(.3) Post-Tertiary and recent beds. 



