Vol. 65.] KARROO SYSTEM IN NORTHERN RHODESIA. 419 



Plats, made up of sandy loam and clothed with dense vegetation. 

 Some 6 miles farther on, fine greenish and red sandstones appear 

 in a creek, with a westerly dip of 5°, changing to a grey coarse 

 deposit. At Jimkola's village and in the Hanyani River are beds 

 dipping 10° southwards, made up of a fine buff sandstone, 100 feet 

 thick, overlying 20 feet of conglomerate containing boulders of fine 

 sandstone 18 inches in diameter. Under this is a grit, made up of 

 quartz, granite, calcareous nodules, and micaceous sandstone, etc. 

 from the escarpment ; also shale and one piece of melaphyre were 

 seen. The sandstone-boulders weather out easily and give rise to 

 potholes. These beds seem to be of post-Karroo age. 



The Angwa, near its junction with the Hanyani, is from 200 to 

 300 yards wide, with a sandy bed and many shingle-mounds. In 

 ascending this, strata of Karroo characteristics are met : sand- 

 stones near the Anglo-Portuguese boundary form a river-cliff 

 30 feet in height-, and at Nyamafega's they show current-bedding 

 and potholing ; they dip north-eastwards at 10°. In a creek near 

 here are bluish shales and clays. Farther south, there are fine 

 fissile sandstones (micaceous) with carbonaceous specks and ripple- 

 markings, and harder compact beds, dipping 15°. The latter are 

 jointed vertically, and water-erosion in a stream has widened the 

 joints out, until the rock stands in columns 6 inches apart and 

 24 inches high. 



Prom this point southwards there is a considerable development 

 of sandstones, forming low hills that extend to the plateau-margins 

 15 miles away. The rock breaks into big blocks, and is frequently 

 incised in deep kloofs by torrents. 



I must now refer, as briefly as possible, to the margin of the 

 Karroo deposits on the northern side of the Zambesi Basin, namely, 

 around the Lufua and Losito Rivers, which join the Zambesi above 

 its confluence with the Kafue. There again the escarpment-feature 

 •is in evidence, overlooking the valley towards the south, and 

 extending, like a Avail, far to the north-east. (See fig. 3, p. 41 6.) 



The Lufua River. 



From its source near the Monze Mission (altitude 3900 feet), this 

 Tiver takes an easterly course and deepens a valley, in Archaean 

 rocks, 1250 feet before reaching the basin of Karroo strata 20 miles 

 away. The unconformable base occurs on the slopes of a hill- 

 side, and there is a succession of conglomerates and broad coal- 

 measnres, lying in a narrow basin a mile and a quarter long and 

 800 yards wide — in a cliff of which the strata are visible in 

 PI. XXII. This, the Malembi, is separated from a second and 

 larger basin, the Katonda, by an anticlinal dome of gneiss, through 

 which the Lufua passes by a ' poort.' Another similar dome divides 

 this from the open Bonda Flats, and again there is a river-gorge. 



The two valleys mentioned are due to two symmetrical folds, 



