DIABASE OF TASMANIA. 251 
NOTES ON THE DIABASE OF TASMANIA AND ITS 
RELATIONS TO THE SEDIMENTARY ROCKS 
WITH WHICH IT IS ASSOCIATED. 
By T. StepHens, M.A., F.G.S. 
THE object of this paper is to give a brief retrospect of some 
of the leading facts and theories already brought forward, _ 
to supplement this by evidence furnished by the author's 
own experience during many years’ general acquaintance 
with the greater part of Tasmania, and to offer suggestions 
which may help towards the solution of a difficult probiem. 
The subject naturally divides itself into two principal 
heads—(I.) the age of the diabase (otherwise described as 
dolerite, or gabbro, and popularly known as greenstone), in 
relation to the accompanying sediments, and (II.) its char- 
acter, present aspect, and mode of occurrence. 
I. The earliest systematic attempt to investigate the geo 
logical history of Tasmania appears to have been made by 
Count de Strzeleckiduring the period 1841-3. His report (') 
shows that Strzelecki was fully convinced, after a long course 
of wide-reaching and arduous exploration, that the occur- 
rence of the diabase is everywhere marked by signs of its 
intrusive character. Of rocks at Eastern Marshes belong- 
ing to the series now known as Permo-Carboniferous, he 
says (p. 116) that they “ have been much fractured and dis- 
located by the intervening greenstone.’”’ Referring to the 
coal-measures high up on the southern face of the diabase- 
capped Ben Lomond, he notes (p. 126) the presence of “‘a 
seam of coal with conglomerate and sandstone dislocated 
and uplifted 2100 feet above the actual level of the coal 
beds.”’ All his other remarks on these rock-relations are to 
the same effect. 
In 1842 Tasmania was visited by the late J. Beete Jukes, 
whose views respecting the relations of the igneous and sedi- 
mentary rocks are recorded in his “‘ Notes on the Paleozoic 
Formationsof New South Walesand Van Diemen’s Land. (*) 
After remarking on the great complexity of the geological 
structure of South-Eastern Tasmania, owing to the mutual 
interlacement of the sedimentary and igneous rocks, he gives 
numerous instances where the Upper Palzozoic marine beds, 
(') Physical Description of New South Wales and Van Diemen’s 
Land. Longmans, 1845. 
~ ey Journal, Geological Society, London, Vol. iii., 
p. : 
