Obler B<tmifs of Greenshoroiujli, etc. 51 



district younger tlian the peneplain; whilst if the Kangaroo 

 Ground basalt be a monadnock on the peneplain, there is a great 

 gulf between the respective Older Basalts of the two places. If, on 

 the other hand, it be not a monadnock, but part of a flow subse- 

 quent to the formation of the peneplain, both it and the Greens- 

 borough rocks would probably be of the same age, but separated 

 from the Koyal Park flow by a great interval of time. 



The point might be satisfactorily settled if the age of the sedi- 

 ments below the respective basalts at Kangaroo Ground and Green.s- 

 borough could be determined beyond doubt, but unfortunately no 

 fossils have been discovered at either place, and thus the most 

 reliable proof is absent. 



The proximity of the two areas, the generally similar characters 

 of the underlying sediments, and the roughly level, continuous sur- 

 face over which the basalts have flowed suggest their identity in age. 

 In favour of their difference is the uneven valley-like surface on 

 w'hich the Kangaroo Ground basalt in part rests, and the dis- 

 crepancy in the character of the rocks (vesicular and dense) already 

 noted, but these are of a soraew^hat frail nature on which to make 

 H great time gap. Provisionally, therefore, these basalts may be 

 held to be of the same age, and as the Greensborough Older Basalt 

 belongs probably to the Kalimnan or later period, the Kangaroo 

 Ground basalt must tentatively be placed there. If this be correct, 

 the latter is not a monadnock on the Nillumbik Peneplain. 



No distinct vents have been discovered in the basalts of Greens- 

 borough or Kangaroo Ground. Garden Hill, at the latter place, 

 rises considerably above the general level of the surrounding basalt 

 and it is just possible that this may represent the worn-down vent 

 from which the lava was spread over the country. 



Streams cut through the Older Basalt at Greensborough, but are 

 deflected away from that at Kangaroo Ground. Either a monad- 

 nock on the old peneplain or a high mass (such as exists), due to 

 being the remains of a vent, would cause this peculiarity. 



The Mount Cooper Newer- Basalt. 



As previously indicated, the basalt forming the cap of Mt. 

 Gooper, Bundoora, is shown on the Survey Quarter-Sheet as con- 

 tinuous with the Newer Basalt flows on the plain to the west. On 

 a visit to the locality some years ago, the writer accepted this view, 

 but in consequence of subsequent examination of the Greensborougli 

 basalts, and the high-level basalt at Ivanhoe, together wnth the dis- 

 tribution of the basalt around Mt. Cooper, as shown by the map. 



