The area of the centre of the Java Sea is held to represent the surface 

 of an old peneplained region, the monadnocks of Banka and Billiton 

 being relicts of the granites occuring in the area of original pre-Tertiary 

 formations. 



The northernmost area is comprised of the Borneo, Malacca, and 

 South China Sea associations. The Borneo group is characterized by 

 andalusite (up to 78 per cent.) in the eastern part (I), the amount of 

 epidote increasing towards the west (II) . Type I covers the peneplained 

 Banka-Billiton part of the old Sunda continent, II was sedimentated on 

 the northern part consisting of Malacca and South China Sea group. 



The Meratus-Plaut group is separated as being derived from the 

 island Pulu Laut and the metamorphic rocks of the Bobaris-Meratus- 

 Mountains of south-east-Borneo. 



The Malacca group is distinguished because of the typical ragged 

 features of the hypersthene and of the habit of the hornblende, which 

 makes a close relationship to Scrivenor's " Pahang Volcanic Series" 

 obvious. 



Summary of Discussion 



At the request of Mr. PoweU, Dr. van Baren proceeded to supplement 

 his address with an indication of the source and nature of each of the 

 bottom materials plotted. Illustrating from maps and charts, he directed 

 attention first to a region north-west of Java, where volcanic influence 

 was marked and the bottom sediments included volcanic glass and other 

 igneous derived material. But some samples from this same region were 

 found to have no relation at all to volcanic areas. One sample from the 

 Bay of Batavia included rounded garnets, appearing like fragments of 

 shore sand, but having, no relation to the shore deposits of the present 

 day. This material probably represented a sand deposit of an older 

 period. Hornblende, amphiboles, augite, and hypersthene were cited 

 among the other minerals represented. 



The area of the centre of the Java Sea was held to represent the surface 

 of an old peneplained region with granites, and with tin deposits 

 associated. A large mass to the east of Borneo consisted of Tertiary 

 sediments derived from the south seas, which in Tertiar};^ times has come 

 as far as the west of Borneo. Metamorphic materials played a large 

 part in the composition. 



Dr. Shepard inquired whether the sediments described could not 

 have been carried out after river cutting ; the sediments might have been 

 carried out from various petrographic provinces so as to cover up 

 the original river deposits. He agreed that sections and cores would be 

 needed for conclusive statements to be made. Dr. Kuenen referred to 

 Pettersson's cores through 5 metres of recent deposits. Dr. Emery 

 inquired as to the occurrence in the area of phosphorite. This had not 

 been encountered in significant proportions, but the occurrence of 

 glauconite was described. 



Dr. Kuenen questioned the validity of the Rhine comparison by Dr. 

 Shepard. Material from various provinces might at some depths be 

 covered up by recent deposits but in the Rhine mixed recent material 

 "was very widely dispersed by the distributaries of the delta. Dr. van 

 Baren stressed that in all these examples greater depth samples were 

 needed. 



219 



