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CHARACTER AND FAUNA OF THE RIVERSDALE 

 AND UNION FORMATIONS. 



(J. E. Hyde.) 



The Riversdale and Union formations are each very 

 thick. The combined thickness has been estimated to be 

 10,000 feet (3,050 m.) and this is probably not exaggerated. 

 The Riversdale, which is the older, is composed of 

 grey, red and purplish shales, with sandstone beds. It 

 differs from the Union in the greater proportion of 

 grey shales, the Union being almost without exception 

 bright red in colour. There is, however, a considerable 

 thickness of red shale in certain portions of the Riversdale . 



The strata are evenly bedded and are clearly water laid. 

 Only occasionally are there evidences of strong current 

 action. Mud-cracked beds are not infrequent and the 

 sandstones are composed frequently of undecomposed 

 rocks and mineral fragments. Rarely does a thin bed of 

 coal occur in the Riversdale. 



The fauna and flora which have been described from the 

 " Riversdale-Union " series appear to have been collected 

 largely from the upper part of the Riversdale, but the exact 

 localities and horizons have not been specified. Although 

 the Union formation is almost barren, the writer has 

 obtained the same fauna with Leaia and Anthracomya in 

 beds almost at the top of the Union at Union station, 

 where plant remains also occur. Both the fauna and flora 

 are abundantly preserved in numbers of individuals if not 

 in species, in the upper beds of the Riversdale at railroad 

 cuts a short distance east of Riversdale station. Eastward 

 from these cuts these remains are observed less often. 

 Here and at every point where they have been found 

 by the writer, the faunas are confined almost entirely to 

 the beds of grey shale. Very rarely indeed are remains 

 found in the red shales. The Leaia is most commonly 

 found in beds of slaty, almost black shale. This same mode 

 of occurrence obtains in the Point Edward formation at 

 Sydney, believed to be an approximate equivalent of the 

 Riversdale and Union, or of some portion of them. 



