54 E. 0. Teale: 



D. Lower Palaeozoic Sediments. 



Ihese are found enclosing the diabase on all sides, except where 

 later dacite porphyry or Upper Palaeozoic sediments overlie it at the- 

 northern extremity. These rocks are mapj^ed as Silurian on the 

 8 inch Geological Map of Victoria, and until the Avriter's examina- 

 tion the only fossil recorded from this region was a Monograptus 

 obtained by Mr. A. M. Howitt, and indentified by the late Dr. T. 

 S. Hall. 



The present field Avork has brought to light other graptolites, 

 ranging from Lower to Upper Ordovician and Protospongia in 

 cherts identical with those of Heathcote now included in the Cam- 

 brian, and j^ossibly also radiolaria in the same cherts. The fact 

 that the graptolites are poorly preserved, and separated by large 

 intervening barren areas, makes the working out of the correct 

 stratigraphical succession in this area very difficult. In fact it 

 would be unwise in the present state of our knowledge in this 

 region to attempt to mark boundaries between the different mem- 

 bers of the Lower Palaeozoic. We can only note that the succession 

 probably ranges from Cambrian to Silurian, and no unconform- 

 ability has with certainty yet been recognised in this region. 



At Heathcote no certain line of division can be drawn between 

 the lowest beds of the Ordovician and the uppermost of the Cam- 

 brian. The Dinesus tribolite beds form ai bench marking the Cam- 

 brian, but above them there is a great thickness of unfossiliferous 

 sediments which seem to pass comformably into the Ordovician. 



In the area above mentioned, and in the Howqua region, it 

 would appear that there has been a continuous sedimentation from 

 Cambrian, through Ordovician, and possibly, too, into Silurian in 

 the last area. The fossil record is, however, unfortunately very im- 

 perfect. 



(a) LIthological Featurta of the Sediments and Apparent 

 Relationships. 



There are certain broad lithological distinctions which are 

 apparent, and features also with regard to the general distribution 

 which call for discussion. 



First, there is a marked lithological contrast on either side of 

 the main diabase area. 



