via a, 5 Pratt and Smith: Petroleum Resources 323 



usual with travertine deposited by streams, the formation is 

 most extensive over faces of waterfalls where beautiful rounded 

 terraces often develop; but wherever the streams flow rapidly 

 enough to break into ripples, travertine is precipitated abun- 

 dantly, and even in still water a veneer of travertine covers the 

 whole stream floor. 



Where the flow is rapid, the travertine is eventually built 

 up so as to raise the stream level. As soon as the travertine 

 forms a barrier in this way it accelerates its own growth and 

 ultimately becomes a natural dam. Stream ponding is thus 

 developed, or the water may be diverted to a new channel ad- 

 jacent to the old bed. A curious interpretation of this phe- 

 nomenon has grown up among some of the prospectors familiar 

 with the Tayabas field. As it is commonly expressed: "Where 

 a river dams itself up, you are close to oil." A possible slight 

 basis for this belief may be found in the fact that the petro- 

 liferous or carbonaceous beds precipitate the calcareous salts 

 from the water, and are usually coated with travertine in con- 

 sequence. However, since decomposing vegetable matter, such 

 as fallen leaves and twigs, and evaporation from the surface 

 of the water are active precipitating agents, this rule of thumb 

 method of prospecting leaves much to be desired. On the other 

 hand, the travertine seriously retards geologic study in that it 

 often conceals the formations along the streams where they 

 would otherwise be open to examination. 



Littoral deposits and recent coral reefs. — Narrow coastal 

 plains, composed mainly of raised coral reefs, occur at intervals, 

 bordering the peninsula. Clay, sand, and other shore materials 

 are intermingled with the corals in varying degrees. The result 

 is a yellow to white, heterogeneous, unconsolidated formation 

 without distinct or regular bedding planes, which is generally 

 youthful in aspect. Shells and fragments of coral closely related 

 to species that are to be found alive in the adjacent seas are 

 prominent constituents of the rock. The disintegration product 

 is a brownish yellow sandy clay which generally covers the 

 ground surface. 



These deposits lie nearly horizontal and are found from sea 

 level to an elevation of at least 15 meters. The coastal plain 

 between the mouth of A jus River and Catanauan attains a 

 greater elevation than 15 meters, but here, as well as elsewhere, 

 it is difficult to delimit the raised reefs from the older coralline 

 limestone. Numerous small areas of mangrove-covered littoral 

 deposits are to be seen farther south along this coast. On the 



