Geology of Southern Nigeria. 74:1 



to which the oldest series has been subjected ; but usually they 

 are practically unchanged. There is no definite evidence to show 

 i;o what period they belong, but they are certainly Pre- Cretaceous^ 

 probably Middle and Early Palaeozoic. 



So far as observed, there is a great hiatus between the Pre- 

 Cambrian and the next known sediments, the "Upper Cretaceous. 

 Normally, these are slightly inclined rocks : they include 



(1) Marine fossiliferous shales, mudstones, limestones, and sand- 

 stones in the great valley between the Oban Hills and the Udi 

 plateau. The fossils are principally ammonites and mollusca ; 



(2) Estuarine fossiliferous carbonaceous shales, mudstones, and 

 sandstones along the eastern foot of the Udi escarpment ; 



(3) Lacustrine sandstones, shales, and black coal-seams, with 

 numerous plant-remains ; and (4) Fluvio-lacustrine sands, shales, 

 and pebble-bands in the lower and upper parts of the Udi plateau. 



Flanking this plateau on the south and south-east, and extending 

 thence over the southern part of the great valley to the Cross River, 

 is a series of Eocene estuarine shales, clays, and marls, with septarian 

 nodules and pieces of coal and resin, and a rich fauna consisting 

 principally of mollusca, but including fragmentary remains of 

 whales, birds, fishes, and turtles. 



A thick series of sandstones, mudstones, shales, and seams of 

 brown coal forms a large portion of the basin of the Niger, west of 

 the Udi plateau. These rocks appear to be of lacustrine origin, 

 and are probably Eocene. They contain numerous remains of un- 

 determined plants, largely of dicotyledonous types. Their relation 

 to the Cretaceous and to the Eocene estuarine series is uncertain. 



In the Ijebu Jebu district are bituminiferous sands and clays 

 with Pliocene estuarine shells. 



Extending over practically the whole of the country south of 

 lat. 7° 10' N., and west of the great valley of the marine Cretaceous is 

 -.a varying thickness of (usually unstratified) clayey sands, probably 

 late Pliocene — the Benin Sands Series of Mr. J. Parkinson. 



Along the coast-line and extending for considerable distances up 

 the Niger and Cross Rivers are fluviatile, deltaic, littoral, and swamp 

 gravels, sands, and muds of Pleistocene and recent age. In the 

 Cross-River basin, intruded into the marine Cretaceous, are volcanic 

 necks of decomposed agglomerate, and sills (?) and dykes of olivine- 

 dolerite. These are probably Pre-Eocene. 



Faulting and local folding are visible in various portions of this 

 district. Numerous silver-lead-zinc-iron lodes occur along these 

 fault-lines, with brine-springs in several localities. 



The Yorubaland crystalline rocks contain magnetite in considerable 

 quantities, while these and the crystalline rocks of the Oban 11 ills 

 show smaller quantities of cassiterite, gold, monazite, and columbite. 



2. ' Notes on the Extraneous Minerals in the Coral-Limestones 

 of Barbados.' Bv John Burchmore Harrison, C.M.O., M.A., 

 F.G.S., F.I.C., and C. B. W. Anderson. 



Characteristic representative specimens of the fossil reef-corals 

 and of the beach-rock of the high-level and low-level limestone 



