EARLIER TERTIARY (EOCENE AND OLIGOCENE). 715 



Limestones occur interstratified in tlie marl, in rather thin beds, and of ooUtic or 

 even suhcrystalline texture. Corals are of common occurrence, especially a species of 

 Orbicella. * * * 



The Tamana calcareous series consists of the massive limestone of Tamana, L'Ebranche, 

 and Montserrat, which varies from white to yellow in color and from granular to crystalline in 

 texture. These strata have experienced a very complete change of structure, the particles 

 being entirely rearranged, which is most beautifully exemplified in the obhteration of the fossil 

 corals, whose exterior surfaces are well preserved, but toward the interior all organized texture 

 gradually fades into the crystalline mass. 



This is the most definite stratum of the whole island, and can be traced, with only two 

 or three interruptions, from near the western to the eastern coasts. There is only one common 

 coral (a species of OrbiceUa) which also occurs in the limestones of the Naparima marl. The 

 stratification being usually obliterated, the dip can be but rarely determined and is always found 

 to be to the northwest, at an angle varying from 30° to 70°. The thickness can not be less 

 than several hundred feet. 



The beds of conglomerate are composed partly of rounded pebbles of indurated sandstone 

 and jasperized clays from the Older Parian, and partly of quartzose detrital from the northern 

 hills (Caribbean group). The cementing matter is ferruginous, calcareous, or sUiceous. These 

 conglomerates are generally highly consolidated. 



Calcareous sand and sandstone form a marked feature in this succession of strata. The 

 former are loose, with a certain, usually small admixture of calcareous, often sheUy matter, and 

 occasionally traversed by layers of hard calcareous sandstone. The latter consist of grains of 

 sand, with calcareous cement, which is frequently fine organic debris or larger shelly fragments, 

 and form hard beds of a few inches to 20 or 30 feet in thickness. Both these varieties of strata 

 contain abundance of marine shells and have supplied the larger proportion of the animal 

 fossils collected in the island. 



The remaining strata of the series consist of sands and clays, more or less fossUiferous, but 

 not consohdated. 



The sequence of strata is exposed in the cliffs at Manzanilla. The thickness, including the 

 crystalline limestone, may be about 2,000 feet. * * * 



The crystalline limestone seems to form one of the lowest members, over which are cal- 

 careous sandstones, conglomerates, and calcareous sand, above which are fossiliferous clays and 

 sands. * * * 



The Caroni or carbonaceous series is exposed in a complete section in the cliffs between 

 Manzanilla and the Oropuche. Two divisions may be introduced — the lower or noncarbona- 

 ceous and the upper or carbonaceous. The former consists of shales, generally dark gray; 

 dark, often black fossiliferous clays; a few thin beds of sand, frequentty sulphurous, and asso- 

 ciated with a small number of pebbles from the Caribbean and Older Parian groups; and in the 

 upper part of highly laminated but unfossiliferous hard, calcareous sandstone. The superior 

 division contains strata composed of sand, with small pebbles of the usual varieties, shelly 

 fragments, and calcareous cementing matter. The rock of Point Noir is an illustration of this. 

 Of shales there are all varieties, from hght-colored to dark carbonaceous. The clays are 

 frequently carbonaceous and sulphurous. 



Beds of massive yellow but pulverulent sand generally overhe the larger seams of coal, with 

 only a few feet of shale intervening. 



Subordinate layers of calcareous sandstone, usually only a few inches thick, occur in places. 

 The seams of Tertiary coal associated with the preceding strata form an important item. They 

 are numerous and vary from a mere carbonaceous film to over 4^ feet in thickness. * * * 



The lower strata of the upper division contains shells similar to those at Manzanilla, but 

 the superior beds are characterized by large shells, which are believed to be confined to that 

 portion of the series. A few dicotyledonous leaves occur in the nodules of calcareous sand or 

 clay. * * * 



