170 ME. JIJKES-BEOWNE AN^D PROF. HARRISON 



16. The Geology of Barbados. Part II. The Oceanic Deposits. 

 By A. J. Jukes-Broavne, Esq., B.A., F.G.S., and Prof. J. B. 

 Harrison, M.A., F.G.S., P.C.S. (Ttead January 6th, 1892.) 



Contents. 



Page 



§ 1. General Description of tbe Deposits ; 170 



§ 2. The Minute Structure of the Rocks 172 



I 3. The Chemical Composition of the Rocks 182 



§ 4. Organic Remains found in the Rocks 193 



§ 5. Stratigraphical Description of the Oceanic Deposits 201 



§ 6. Detrital Deposits of intermediate date between the Oceanic 



Series and the Coral-rocks 214 



§ 7. Notes on the existence of similar Deposits in other West 



Indian Islands 217 



§ 8. Changes in the Physical Greography of the Caribbean Region 



during Tertiary time 221 



In a former paper we described the raised coral-reefs of Barbados ; 

 we now offer an account of the important series of raised oceanic 

 deposits which form part of the solid framework of the island, 

 beneath its comparatively superficial coating of coral-limestone. 



§ 1. General Description of the Deposits. 



(a) Geological Position. — The Oceanic Deposits form a group or 

 series of beds which is clearly marked oif from tbe Scotland Series 

 below and the Coral Limestones above. They do not, however, 

 appear as a continuous band between the other two formations, 

 because the elevation of the island from oceanic depths was accom- 

 panied by a considerable amount of faulting, and tracts of the 

 Oceanic Deposits were dropped down between blocks of the older 

 Scotland Series. Waves and currents then formed a surface of 

 erosion across the faulted mass before the corals began to grow, 

 and consequently the reefs rest, not only on various parts of the 

 Oceanic Series, but in many places directly on the Scotland Beds. 



The unconformity between the Oceanic Deposits and the Scotland 

 Series on which they rest is as clear as the lithological contrast 

 between the two formations is great. The older series has been 

 thrown into a succession of folds and flexures which in many places 

 amount to plications and contortions, and all this compression was 

 accomplished before the formation of the Oceanic Deposits, which 

 often rest on the edges of highly-inclined or vertical strata. In 

 respect of colour and lithological composition there could hardly be a 

 greater contrast than that which exists between the two formations. 

 The older series was evidently laid down in shallow water bordering 

 a large land-area ; it consists of coarse grits, brownish sandstones 

 (coarse and fine), mottled clays (grey, brown, and yellow), with 

 several hundred feet of dark sandy clays, in places saturated with 

 petroleum. The Oceanic Deposits, on the contrary, consist chiefly 



