134 



Bui^ETtn 35 



282 



PAPER No. 17. 



SECOND NOTE ON THE MARBELA MANJAK MINE 

 Dept. Agr. Trinidad, Bull. Agr. Information, Jan-Apr., 

 1909, pp. 51-54. 



Page 51 



Having been favoured by James Wilson, Esquire, of Messrs. 

 Goodwille and Wilson, with samples of the rocks found in the 

 Marbela Manjak mine, I was enabled to present a short prelimi- 

 nary note on the subject published in the Proceedings of the Vic- 

 toria Institute, 1904, and in the Geological Magazine, London, 

 1904, page 276. 



The receipt of additional samples of b the rocks, the last of 

 which came through L. J. Bernstein, Esquire, induces me to 

 modify my opinion on some points, and I therefore contribute a 

 second note on the subject. 



Down to a depth of about 40 or fifty feet the material ob- 

 tained in sinking the mine is mostly of a heterogeneous character, 

 showing extensive disintegration and disturbance due partly to 

 pluvial and weathering agencies and partly to human interfer- 

 ence. Below that we have indurated clays and sandstones con- 

 taining gypsum, and it is in these and the subjacent strata that 

 the manjak occurs in veins and seams. These continue down to 

 about 160 feet, and were apparently laid down in an area where 

 tide-water and flood- water were alternately admitted. These de- 

 posits were extremely . fine grained and the clastic matter in them 

 is mostly very fine sand with a large proportion of argillaceeus 

 matter, showing that its origin was at a considerable distance. 

 But below this the fluviomarine character gives place to a decid- 

 edly marine one, though the proportion of calcareous matter is 

 still much less than in the typical Naparima rocks. These rocks 

 show the gradual shoaling of the water by matter brought down 

 by the rivers from the neighboring continent. The foraminiferal 

 fauna which in the lower beds is of an entirely deep sea character 

 becomes gradually driven out, and only those species remain 



