847 



the bone-beds south of the G. Pandar overlie unconformablj the 

 recent tertiary marls — though he also admits a sliglit u[)heaval 

 of these beds — but first of all the unconformability indicated by 

 him in a profile is not at all in keeping with his own researches 

 (inclination of the marls far too sharp); secondly, the supposed un- 

 conformability is based on the junction of two bonebeds that are 

 wide apart from each other (Dungbrubus and G. Bulak), though 

 only a minute study of details can tell us whether there is, oi' there 

 is not, any fault between the finding places; anyhow their junction 

 is not borne out by local observation. 



The subsidence on the boundary between pliocene and quaternary 

 gave rise to upheavals of the order of 1000 — 2000 m. in Eastern 

 and Central Java. The mountain range thus engendered has been 

 almost completely ])eneplaned in the quaternary, after which, on 

 the thus formed peneplain, the most recent foi'mations of some 

 volcanoes i.a. of the Ungaron and the Merbabu have been deposited, 

 as may be beautifully seen on the railway-line between Kedung 

 Djati and Willem 1 ^). After a, probably vertical, very young 

 upheaval the present valleys penetrated far into the marl-zone 

 through the overlying volcanic deposits. 



The subsidence was, then, succeeded by a denudation of 1000 — 

 2000 Meters, which with an annual denudation of 2 mm. must have 

 required a period of 500000— J 0000000 years, the length of the 

 quaternary period in Java. This very rough estimate does not badly 

 correspond to a recent estimate of the length of the quaternary 

 period in Europe, fixed by Penck in 1908 at 500000 years "). 



The average height of the volcanic massifs (without reckoning 

 the peaks) in Java may be fixed at a number of the order of 1000 m. 

 With a yearly denudation of 0.5 mm. this would point to total 

 disappearance of the present volcanoes of Java in 2000000 years. 

 If, in this connection, we bear in mind that it has generally been 

 admitted that the Tertiary has lasted many times longer than the 

 Quaternary, it is easy to conceive that "old-miocene" volcanoes in 

 Java can hardly be expected to possess discernible crater-rims. Never- 

 theless Verbeek and Fennema "), have indicated discernible crater-rims 

 for numerous volcano-massifs — which they pretend to be "old- 



') 1 must advance liere that though I am personally acquainted with this part 

 of Java, I should hardly have observed these features of the landscape on a short 

 excursion, if the results of an inquiry by Dr. W. Hotz, who made a geological 

 map of this region in 1911, had nol come to my knowledge. 



2) In E. Dacqué, I.e. p. p. 273. 



5) R. D. M. Verbeek and R. Fennema I.e. 



60* 



