33 



NOTES ON THE GEOLOGY OF MARIA ISLAND. 



By W. H. Clemes, B.A., B.Sc. 



Plates XL, XII. 



(Received 2nd June, 1919. Read 14th July, 1919.) 



These notes are intended as an incentive to future 

 study rather than as a complete record of tlie geology of 

 thisi interesting locality. They are the result of several 

 holidays spent on the island, and particularly of two 

 j-achting trips undertaken recently. In many places the 

 record is meagre, as I was unablei to land and examine 

 the rock formations in detail, but had to rely on obser- 

 vatioiis made v;hile sailing along-, often in somewhat 

 troubled waters. Still the deiscription is complete 



enough to be of value, especially as no previous record 

 has been made, with ^the excepton of the late R. M. 

 Johnston's description of the Fossil Cliffs in his Geology 

 of Tasmania. There is brief mention of a. paper read by 

 him before the Royal Society on Riedle Bay, but unfor- 

 tunately it was net printed and his valuable observations 

 havo been lost. 



Maria Island is situated on the East Coast, almost 

 opposite to Spring Bay and Orford. The passage b*eitween 

 it and the mainland varies in -width from three to eight 

 nailes. In the narrowest part, off Long Point, is Lachlan 

 Island, a small diabase rock covered with sparse vegeta- 

 tion. This passage is the result of excessive waive-erosion 

 acting on the sandstones a-nd diabase which are now found 

 fringing eitheir shore. There is little doubt that the 

 Orford sandstones were once continuons with the sand- 

 stones at the Orayfish Rock, a little to the south of 

 the Settlement, and those on the flank of Mt. Maria. 

 The pass-age itself is extremely shallow with a moderately 

 flat floor, the average depth being about six fathoms. 

 A shoal stretchesi across from the Sandspits to beyond 

 Lachlan Island, the water on which is in places only one 

 faithom in depth. The sediment here deposited was largely 

 brought , down by the Sandspits River, which has, at the 

 same time, built up a large alluvial flat and ti-tree swamp 

 covering many acres. The ti-trea is growing on soft oozy- 

 mud, which quivers and shaJies as one passes over, and it 

 is quite easy to shake a considerable area and make the 

 trees bob and curtsy in a rather alarming fashion. There 

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