l^OTES ON THE SECTION AT ONE THEE POINT, 

 NEAR HOBART. Plates iii. to ix. 



By FiiiTz NoETLiNG, M.A., Ph.D. 



(Read July 14, 1913.) 



]. Introductoky Remarks. 



More than tJiirty years ago Mr. R. M. Johnston, in a 

 paper (1) read before this Society, pointed out the great 

 geological interest of a section exposed on the western side 

 of Brown's River-road, near One Tree Point. On the 

 whole Mr. Johnston's observations hold good up to the 

 present day, though some details have to be altered. Mr. 

 Johnston has shown that we have here a volcanic rock of 

 the Basalt-aronp overlying sedimentHry rocks, which con- 

 tain an abundance of plant remains. The most important 

 of these Mr. Johnston sent to the late Baron von Mueller, 

 who was able to identify them with species well-known 

 from the auriferous drifts of Victoria. In itself this 

 would 1 e a most important fact, but the flora, according to 

 the Baron's determination, is of such an extraordinary 

 nature, that it would be almost unique, if his determinations 

 ■could be accepted as correct. 



Many years later Messrs. McLeod and White examined 

 the Basalt, and came to the conclusion that it is a basalt 

 in which Fayalite, the red variety of Olivine, has replaced 

 the Augite and Olivine (2). 



I have frequently studied this section, remarkable in 

 more than one way, and I have come to the conclusion 

 that it allows for an intei-pretation quite different from 

 that given by Mr. Johnston. The main point on which I 

 differ from him is of tectonical nature. Mr. Johnston 

 thinks that the southern pori}ion of the section has been 

 thrown up, but a careful examination has convinced me 

 that it is not the southern portion that has moved, but the 

 northern one ; further, there is not an up-throw of the 



(1) Notes showing that the Estuary of the Derwent was occupied 

 by a fresh water lake during the Tertiary Period. These Papers and 

 Proeeedinos, 188 1, p. 74-. 



(2) Notes on a Favalite Basalt from One Tree Poini..— These Papers and 

 Proceedings, 18J8-1899, page 77. 



