ANDEEWS: LIMESTONES OF THE FIJI ISLANDS. 45 



The Lau Limestones. 



(a) A soft, porous stone, full of corals in situ, shells, and a little cal- 

 careous cement. The corals are no more compacted than one would 

 expect to find in the reef area. The stone is usually white or yellow in 

 color. A thin crust of hard material has gathered over the soft inte- 

 rior. This crust, as well as the reef or coral talus itself, is extremely 

 cavernous. This represents the raised coral material of the last 

 upheaval. 



(6) A dense white rock, ringing under the hammer, generally exhibit- 

 ing little or no trace of well-defined fossils. This is the raised limestone 

 found near sea-level ; it is contemporaneous with (a), and represents the 

 part of the "raised reef" platforms that is composed of the firmly 

 cemented reef debris. 



(c) A compact stone ringing under the hammer containing corals. 

 The color is white or yellow. It is pitted and cavernous, and weathers 

 into long needles. This forms the roughest and most broken country in 

 Fiji. It is the older coral mass of the high levels. 



(d) A rock similar in hardness, but presenting a marked difference in 

 weathering, due to the difference of erosive influences on a homoge- 

 neous rock and one varying considerably in minute structui'e. The 

 coral reef is honeycombed, while the rock under consideration shows 

 perfect examples of the minute-ridge structures. It is, as a rule, non- 

 fossiliferous and homogeneous in structure. Such rock is found at the 

 higher levels and represents the compact debris of pre-existing reefs. 

 This is well seen at Ngillangillah. 



Of other formations we may note a stratified limestone, white, yellow, 

 and brown in color, exceedingly compact and free from honeycombing or 

 cavernous weathering. Very fine-grained rock, and apparently barren 

 of fossils. This is the basal limestone underlying the reefs to the north 

 of Vanua Mbalavu. 



A brown to red ferruginous mass, found encrusting the coastal cliffs 

 at sea-levels. In the huge gaps cut out by the sea in the limestone cliffs 

 these ferruginous masses simulate stalactitic and stalagmitic growths. 

 Redeposition of calcareous matter charged with higher oxide of iron 

 than was present in the rock prior to solution, or from the magnetite 

 mentioned before, explains this stalagmitic growth. In some places this 

 redeposition has advanced so far that the former sea-ledges are partly or 

 wholly obscured. 





