Age of Ironstone Beds of the Mornington Peninsula. Ill 



Further Evidence of the Miocene Age of the 

 Ferruginous Deposits. 



A few months ago my friend, Mr. J. H. Young, of Meredith,, 

 who is already known as an enthusiastic and successful collector- 

 of fossils, paid a visit to Watson's Creek, near the intersection. 

 of the Pearcedale and Somerville Roa,ds, half a Hgirile west ol 

 Baxter railway station. He there found an ironstone band 

 crossing the creek, which contained fossil casts,. Several clearly 

 identifiable specimens of Pecten praecursor were found there,. 

 a species which is typical of the Janjukian. The matrix in 

 which the fossils occur is a fine-grained ironstone,, with small 

 patches of limonite, minute flakes of micaceous iron-ore, and 

 also small, numerous wind-polished quartz grains scattered, 

 throughout. Besides the Pectens there are numbers of small 

 fragments of polyzoa present, but indeterminable. These 

 polyzoa are in such abundance as to lead one to infer that the 

 ironstone is largely a replacement of a limestone comparable 

 with the polyzoal rock of Batesford and Grange Burn. This, 

 replacement at a later stage, of calcareous by limonitic material 

 seems precisely similar to what has happened in some of the 

 '* Gold Drifts " as at Stawell, referred to above, which are to- 

 some extent re-sorted or reman ie beds, the same characters, 

 being also borne by certain of the ferruginous beds of the- 

 Mornington Peninsula. 



Conclusions. 



(1) The lower part of the ferruginous series of sandstone- 

 and fossiliferous ironstone on the Mornington Peninsula from- 

 Frankston southwards is without doubt of Janjukian. (Miocene) 

 age. 



(2) The fossiliferous ironstone appears to have originated 

 from a more decidedly calcareous rock, and in some cases equi- 

 valent to a polyzoal limestone in its included fossils" and original' 

 chemical composition. 



(3) The change from limestone to ironstone has in some- 

 cases been brought about by a percolation of dissolved car- 

 bonate of iron, causing an interchange of bases, the- replaced! 

 carbonate of iron afterwards becoming oxidised".. 



