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NOTES OX THE GEOLOGY OF MARIA ISLAND. 



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



Plates XL, XII. 



(Received 2ncl June. 1919. Bead Utli July. 1919.) 



These notes are intended as an incentive to future 

 study rather than as a complete record of the geology of 

 this interesting locality. They are the result of several 

 holidavs spent on the island, and particularly of two 

 yachting trips undertaken recently. In many places the 

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

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

 vations made while sailing along, often in somewhat 

 troubled waters. Still the description is complete 



enough to be of value, especially as no previous record 

 has been made, with the exceptoa of the late R. M. 

 Johnston s description of the Fossil ClilTs in his Geology 

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

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

 tunately it was not printed and his valuable observations 

 have been lost. 



Maria Island is situated on the East Coast, almost 

 opposite to Spring Bay and Orford. The passage between 

 it and the mainland varies in width from three to eight 

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

 Island, a small diabase i'ock covered with sparse vegeta- 

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

 acting on the sandstones and diabavse which are now found 

 fringing either shore. There is little doubt that the 

 Orford .sandstones were once continuous with the sand- 

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

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

 The passage itself is extremely shallow with a moderately 

 flat floor, the average depth being about six fathoms. 

 A shoal stretches across from the Sandspits to beyond 

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

 fatliom in depth. The sediment here deposited was lai-gely 

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

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

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

 mud, Avhicli quiver.s and shakes 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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