530 ME. E. J. LECHMEEE GTJPPY 0^ THE 



an entire disintegration of the rock that its original texture can 

 nowhere be seen except in deep cuttings. All traces of fossils 

 are obliterated. 



The radiolarian marls differ from the foraminiferal marls in 

 some respects. Some of them are equally incoherent when exposed 

 to water and have an equal power of absorption. But the mud 

 they produce is not quite so tenacious ; this is due to the presence of 

 silica in fine division. Other varieties are more coherent and have 

 a larger proportion of radiolaria and a smaller proportion of amorphous 

 silica (or silicate of magnesia). But from the point of view from 

 which we are now looking at them, all these marls, whether 

 derived from the radiolarian or from the foraminiferal deposits, act 

 much in the same manner. 



The marls of the Nariva Series furnish a less fertile soil. But 

 as regards adaptability for road-making they are little, if any, 

 better than the marls of the Naparima Series. 



I think it highly probable that in some of the marls we have 

 a material suitable for the manufacture of cement, though which 

 of them will prove best adapted for the purpose is matter for 

 experiment. Possibly those of the Nariva Series, such as are 

 found in the neighbourhood of Yistabella and Ne-plus-ultra, may 

 be found to possess good qualities. On the other hand some of 

 those on Paradise and Les Efforts may be better in some respects. 



By way of parenthesis I may refer here to a question that has 

 more than once been put to me, that is, as to the nature and 

 origin of the shells found scattered over the surface of the soil in 

 Naparima and other parts of Trinidad. These are generally recent 

 shells and have no connexion with the formations on which they 

 are found. Mollusca taken on or near the shore have been carried 

 up the country for food and the shells have been thrown about. In 

 a few cases fossil shells are found on the surface, but this occurs 

 only where there is some exposure of a shell-bearing stratum. 

 And this is not very common in Trinidad, especially in the Napa- 

 rima district. 



§ 4. The Pointapiee Sectioit. 



Our section of the Naparima deposits ends northward at Taruba 

 Creek. Little can be made of the stratigraphy of the next two 

 miles until we come to the coast-section at Pointapier. A diagram 

 of this was given in the Geological Eeport on Trinidad (sheet No. 2, 

 fig. 2). The details were very imperfectly rendered, and it was 

 scarcely possible that it should be otherwise. Since the time of 

 the Geological Survey a railway-cutting has been made a short 

 distance inland from this shore-section. But even with the aid 

 of this, little additional light can be thrown upon the age and 

 relations of the rocks named by the Geological Survey ' Older 

 Parian ' and considered to be of Lower Cretaceous (Neocomian) 

 age. 



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