96 SECTION AT ONE THEE POINT, 



U.S. TAS. 



southern, but a down-throw of the northena portion. The 

 ends of the leaf beds are turned upwards near the fault, 

 and this admits of only one explanation, viz., that 

 thi« part moved downwards in relation to the southern one. 

 If this view be admitted, the interpretation of the section 

 tak« s a (^lifferenl aspect at once, when we replace tlie down- 

 thrown portion to its original level. I further noticed 

 that the leaf beds of the northern portion are considerably 

 thicker than those of the southern one. Therefore we 

 must assume that, if the portions on either side of the fault 

 originally formed one continuous layer, a considerable part 

 of the leaf beds must have disappeared in the southern 

 (remaining) portion. This observation holds good, whether 

 the southern portion is thrown up as Mr. R. M. Johnston 

 thinks, or whether the northern portion has slid down, as 

 I opine. 



The origin of the curioiis Breccia seems to me still some- 

 what doubtful. Mr. Johnston thinks it represents old 

 landslips which fell in the "lake." There are, however, 

 many objections to such a view, which I will set forth 

 later on. 



This section is perhaps the best illustration of the 

 more modern geological history of Tasmania, and the 

 sequence of strata, as well as its tectonical features, afford 

 a wonderful mass of information regarding the latest phases 

 of the geological evolution of Tasmania. 1 think it will, 

 therefore, be advisable to describe first the section as it 

 now stands, then to' discuss its different membei-^, and, 

 lastly, to deduce those conclusions which seem to afford an 

 explanation of the facts observed. 



2. The Leaf Bed Series. 



Though not ecxposed at One Tree Point, it is pretty 

 certain that the lowest member of the whole series is a 

 yellowish sandstone, but so far the contact of Sandstone 

 and Breccia has not been observed (3). It may be that 

 the latter rests immediately on the Sandstone, or that some 

 beds of different, more argillaceous nature, intervene be- 

 tween the two. On the whole this is of little importance 

 as far as the questions here discussed arc concerned, if we 

 always bear in mind that the Breccia does not fo-rm th<> 

 base of the series. 



(3) A little further towards Hobart a sandstone of yellowish colour 

 appears from underneath the Breccia. There is no doubt that this 

 sandstone belongs to tlie Leaf Bed series, of wlurli it most probably 

 forms the basal member. This question requires, however, further 

 confirmation. 



