GEOLOGICAL OBSKHVATIOXS IN FIJI. 103 



corals, and cement. It was oriiiinally (le})()site(l alon<^ old shore-lines 

 bnt now may often he found far inland. The first variety is not known 

 in the smaller islands. 



The river-coni^lonierates are often very coarse and contain l)()ulders 

 of andesite, basalt, and limestone 2 or 3 feet in diameter. Such 

 deposits are well seen at the Na Roro bluffs 5 or 6 miles from the 

 mouth of the Singatoka river, and are quarried for road-metal, a few 

 miles up the Tamavua river, near Suva. They occur about the bases 

 of eroded hills of basalt and andesite and, near Suva, are overlain by 

 marls which contain occasional, larger boulders. Interbedded with 

 the coarser conglomerates are layers composed of sand and gravels 

 which have been washed from near-by agglomerates and are but 

 slightly water-worn. 



Two varieties of river-conglomerate are known. The first has 

 pebbles and boulders of quartz-porphyry and diorite. It is found 2 

 or 3 miles from the mouth of the Visari river, at the western side 

 of Suva harbor. It is overlain by lava flows of the second andesitic 

 period and hence belongs to the period of erosion in which the folded 

 sediments of central Viti Levu were deposited. Many of the pebbles 

 in the conglomerate are sheared and it undoubtedly underwent the 

 same folding which disturbed the marls of the interior. 



The second variety of river-conglomerate consists predominantly 

 of andesite and basalt debris and appears to have been eroded from the 

 directly underlying agglomerates or flows. The matrix is often a 

 reddish gray paste which resembles a redistributed ash. The Na Roro 

 and Tamavua conglomerates belong in this class. The Na Roro 

 deposit has pebbles and boulders of limestone, eroded from the lime- 

 stones of the interior. The pebbles are usually much silicified. This 

 type of conglomerate is often associated with a calcareous conglom- 

 erate, lying nearer the present shore-line and forming the basal mem- 

 ber of the coastal-plain sediment. 



Calcareous conglomerates unconformably overlie volcanic rocks 

 in many of the islands. They are the basal members of the folded 

 interior sediments, found 40 miles from the mouth of the Singatoka 

 river, near Wai Mbasanga, and also of the coastal-plain series, 

 exposed all along the southwestern coast of Viti Levu beneath the 

 marls. Pebbles of volcanic rocks seldom form over 50 per cent of 

 these deposits. Shell and coral waste with a calcareous cement 

 compose the greater part of rock and, in thin sections, numerous fora- 

 minifera may be seen. By losing their coarser shell and coral material, 

 these rocks grade upward into marls. 



