﻿Vol. 66.] ON THE GEOLOGY OF NYAS ALAND. 20 1 



stones, either white or pale in colour. In the Nkana area, near 

 the Songwe River (A, fig. 2, p. 193), this group has a minimum 

 thickness of 700 feet ; while farther south, at Mpata (B, tig. 2), 

 the thickness is at least 1000 feet. Traced westwards, however, the 

 group thins out, as has already been mentioned. 



Shale, Coal, and Mudstone Division (Division 2). — 

 Above the lower sandstones comes a series of dark shales, dark-grey 

 muddy grits and sandstones, with seams of coal or coaly shale, and 

 in places conglomerates. As a rule the coal is distinctly laminated, 

 and consists of venules of bright coal alternating with dull earthy 

 material or silt. By increase in the amount of earthy material the 

 coal graduates almost imperceptibly into a coaly shale, and thus in 

 some localities it is difficult to draw the line between coal and 

 carbonaceous shale. Near Mount Waller (E, fig. 2, p. 193), however, 

 the coal is of far superior quality to that found in other areas, and 

 compares favourably with good English coal. 



The floor and roof of the various coal-seams present no regular 

 characters, but may consist of either shale, or sandstone, or mud- 

 stone, and in places conglomerate. The usually lenticular character 

 of the seams, their variation in character from place to place., 

 the apparent absence of typical fire-clays and rootlet-beds, and 

 their association at times with conglomerates, are characters 

 which suggest that the coal owes its origin to transport and not to 

 growth in place. The total thickness of this division is small, and 

 probably does not exceed 200 feet. 



Upper Grit and Limestone Division (Division 3). — 

 The coal-group is directly overlain by massive yellow and brownish 

 grits or coarse-grained sandstones, and also mudstones and shales, 

 which latter play a subordinate part. The grits are often highly 

 felspathic, and sometimes slightly calcareous. They are always 

 false-bedded, but the false bedding is generally at alow angle to the 

 true bedding. Lenticular seams of pebbles of vein- quartz occur, 

 especially towards the top of the series : these seams rarely exceed 

 a few inches in thickness. In certain beds, however, the pebbles 

 are not so concentrated, but are distributed evenly throughout the 

 mass of sandstone. Despite the presence of pebble-seams and beds, 

 true conglomerates are rarely found. 



In the north-east of Nyasaland this typically gritty series is over- 

 lain by calcareous beds and mudstones. The limestones are usually 

 grey, very compact and argillaceous. Oolitic limestones and lime- 

 stones of gritty texture are also developed. Near Xkana (A, fig. 2 ) 

 the limestone group, which includes fossiliferous shales and mud- 

 stones, has a thickness of about 150 feet, and is overlain by sandy 

 beds. At Mpata (B, fig. 2), however, the group has swollen to a 

 thickness of at least 700 feet. The limestone group is unrepre- 

 sented in the western areas, but its absence appears to be compen- 

 sated for by the increased development of grits, which probably 

 reach 3000 feet in thickness. In the Mount Waller area (E, fig. 2), 



