academy of sciuch] ASIA AND MALAY ARCHIPELAGO. 33 



Brouwer ('16) has suggested the occurrence of a similar structure and notes the presence of 

 pillow-lavas, probably of upper Triassic age. 



As the Malayan arc swings round the Banda Sea into Timor Laut and Amboina, one finds 

 again immense amounts of peridotite and serpentine invaded by diabase and later by granite 

 and, after erosion, overlain by Tertiary rocks. In Amboina the ultrabasic rocks are the most 

 ancient, but in the adjacent islands of Ceram they have been injected into a mass of schists of 

 unknown age (Verbeek '05). This series of occurrences of green-rocks were grouped by 

 Steinmann ('05) with ophiolitic rocks, and were held to have been formed under the conditions 

 which he described for the genesis of such rocks. (See p. 2.) Mesozoic radiolarite is frequently 

 present in this archipelago (Hinde '08), but Martin ('07) has challenged the assumption that 

 they necessarily represent deep-sea deposits. Brouwer ('19) has discussed the age of the green- 

 rocks of the Molluccas. Some, such as that of Amboina, appears to be probably pre-Permian; 

 much is intrusive into the Mesozoic rocks, and is itself probably of late Mesozoic age, though 

 there are also effusive diabasic rocks and tuffs of Triassic age; some again occur as sills in 

 older Tertiary rocks. It was in early Tertiary times that the great thrusting movements 

 occurred directed toward the south. The development of serpentine of about this age is, 

 however, in immediate connection with pillow-lavas, " concordantly overlying" them, and 

 Brouwer compares this association with the development of picrite with diabases and pillow- 

 lavas in Germany. 



According to Suess, the Philippine Islands, though very imperfectly known, appear to be 

 the region of linking of four lines of Tertiary folding, along which elongated masses of ultra- 

 basic rock may occur. To the southwest are the Palawan line and the Sulu line, to the south- 

 east the Sangi or Celebes line, with a subsidiary line through Halmahera inserted between Cele- 

 bes and New Guinea, while the fourth main line strikes north from Luzon into Formosa. Gab- 

 bros and peridotites are numerous in Halmahera and the adjacent smaller islands and in Celebes. 

 A considerable amount of research work has recently been accomplished in the last island, 

 most of which has not been accessible to the writer. (See Van Waterschoot van der Gracht 

 '14, Abendanon '17, '19, Giswolf '17.) The following has been taken from a review of this liter- 

 ature by Wanner ('19) : 



That the outline and topography of Celebes is determined by recent fractures is shown by 

 both geological and physiographic studies. Central Celebes shows a basement-complex of 

 gneissic and schistose rocks invaded by a series of peridotites, flaser-gabbros, and granites, which 

 farther south in the less altered Latimondjong range show evidence of having invaded Paleozoic 

 phyllites, diabases, and diabase-tuffs. To the east this basement becomes less metamorphosed. 

 According to Abendanon, it formed a continental platform which he terms Aequinoctia, at the 

 close of Paleozoic times. (See Abendanon '19.) This was flooded by Triassic seas, which 

 deposited radiolarite, and after some warping and erosion Cretaceo-Tertiary claystones were 

 deposited unconformably on these. This covering has now been largely removed from the 

 uplifted and dismantled peneplane, though retained in the west and southwest beneath a series 

 of Tertiary andesites, trachytes, rhyolites, and leucite-lavas. The eastern margin of the conti- 

 nental region is determined by a long narrow intrusion ("1,100 meters thick") of ultrabasic 

 rock, extending to the south-southeast from near the Gulf of Tomini past the head of the Gulf 

 of Tolo, and for an unknown distance into the southeastern peninsula. This ultrabasic rock is 

 stated to be "essentially Mesozoic," though the precise age can not be determined. There is 

 abundant evidence of the action of much lateral pressure on the serpentine. Near the Gulf of 

 Tolo it is associated with Mesozoic radiolarite, and Cretaceo-Tertiary marls and limestone, both 

 intensely folded, which movement Abendanon holds to have displaced the passive ultrabasic rock. 

 Farther north the serpentine is associated with steeply dipping and more or less reddish crushed 

 phyllite and diabase-tuff, associated with brick-red radiolarite traversed by white veins, a strik- 

 ing analogy with the features to be described in the Devono-Carbonif erous serpentine belt of New 

 South Wales. A fault-trough separates this serpentine-line from the eastern peninsula, which 

 has been described by Wanner ('10), whose paper is not accessible to the writer. According 

 to Brouwer's citation, gabbro and diabase of Upper Oligocene age occur here. 



