141 

 Division Jf. 



JANJUKIAN LACUSTRINE, CARBONACEOUS BEDS WITH LIGNITE. 



These are fresh water lacustrine beds of very variable 

 thickness which rest, more or less horizontally, upon the up- 

 turned edges of steeply inclined slates and other strata of 

 Lower Cambrian or earlier age, and are overlain by the 

 Jahjukian marine beds. There appears to be some evidence 

 of erosion of the upper limits of the ligneous series, but the 

 extent of such will be better defined as exploration of the 

 field proceeds. 



It is evident, however, that the age of the fresh water 

 lignite-bearing beds is either Miocene or pre-Miocene. It is 

 most reasonable to regard these beds as having formed con- 

 temporaneously with either one or other of the strongly 

 developed Tertiary lignites of the adjacent State, Victoria. 

 Referring to these latter occurrences, the Altona lignite series 

 is intercalated with typical marine Oligocene (Balcombian) 

 fossil bands. But the Morwell beds, so far as can be judged, 

 occupy a former lacustrine or coastal swamp area, of which 

 the hinterland river deposits of the Miocene Dargo High 

 Plains form a part. Judging from the palaeogeography of 

 the region, therefore, the Morwell lignite is Miocene in age. 

 The reference of the carbonaceous lacustrine beds at Moor- 

 lands to the Morwell (Miocene) period is indicated by the 

 fact that they appear tO' be comparable with a similar forma- 

 tion, underlying the polyzoal rock in the mallee, and which, 

 besides containing lignite, includes typical Janjukian marine 

 shells, Trigonia lamarcki, found occurring at the top of the 

 Janjukian, and the foraminifer, Cyclammina comflanata , 

 Chapman, the latter being found at the base of the Janjukian 

 at Anglesea. 



Ligneous beds of a character similar to these at Moor- 

 lands are now being actively explored at three other localities 

 in South Australia, namely, at Clinton, C^) on the west side of 

 Gulf St. Vincent, almost at its northern extremity; at Hope 

 Valley, (^) one of the northern suburban areas of Adelaide; 

 and at Noarlunga,^^) 23 miles south of Adelaide, adjacent to 

 Gulf St. Vincent. Furthermore, similar beds were encoun- 

 tered in a Government bore put down at Bower, (lO) 20 miles 

 west of Morgan, several years ago. There is also other 

 evidence from boring operations in South Australia, indicating 



0)Vide Dept. of Mines, S. Austr. ;,Min. Rev., Nos. 34, pp. 

 29-31, 40, 51; 35, pp. 26, 27, 43-46, 55-56. 



(8)Min. Rev., Nos. 14, p. 10; 20, pp. 19, 40, 41; 33, pp. 25-37; 

 34, pp. 27-29, 33, 41, 42; 35, pp. 13-15. 



(9)Min. Rev., No. 33, pp. 78, 79. 



(lO)Min. Rev., Nos. 20, p. 11; 28, pp. 26-28; 29, p. 23. 



