244 L. F. HARPER. 



THE AGE OP THE SOUTHERN COAL FIELD 

 TABLELAND BASALTS. 



By L. F. Harper, f.g.s., 



Geological Surveyor, Department of Mines. 



[Read before the Royal Society of N. S. Wales, September J, 1915. ,] 



As far as the writer is aware it has been generally taken 

 for granted that the basalt occurrences found on the 

 Robertson and Sassafras tablelands are of Tertiary age* 

 It is intended in this paper to bring forward evidence which 

 it is thought points strongly to their having resulted from 

 a later period of volcanic activity. The grounds for this 

 opinion may be summarised as follows: — 



1. Palseontological evidence, in the form of plant remains 

 obtained from the sediments under the basalts, points to as 

 great an affinity to Pleistocene as to Pliocene forms. 



Consequently these beds may be assigned to a period of 

 deposition not older than late Pliocene. 



2. The uplift which resulted in the formation of the 

 tableland areas took place in Pleistocene time. 



3. The uplift gave rise to the faulting found in the 

 northern portion of the Southern Coal Field. 



4. Subsequent to the faulting, volcanic intrusions took 

 place and the resultant igneous rocks bear a most striking 

 chemical and petrographical affinity to the tableland 

 basalts. 



5. The physiographic disposition of the tableland basalts 

 points to their having in many instances welled over areas 

 of country with drainage channels almost identical with 

 those of the present day, showing but little discrepancy as 

 to stages of maturity in land surfaces. 



