THE 



G1<]0L0GICAL MAGAZINE 



NEW SERIES. DECADE VI. VOL. I. 



No. XII.— DECEMBER, 1914. 



cD:EixG-xi<rj^iL. ^A.i^a?ioi-.ES. 



I.— The Lateritic Deposits of Mozambique. 

 By Arthur Holmes, A.E.C.S., D.I.C., F.G.S., F.E.G.S. 

 (PLATE XXXVn.) 



IN his Last Journals, referring to the formations of Portuguese 

 Nyasaland west of the Lugenda River, Livingstone writes : 

 " The elevated plains among these mountain masses show great patches 

 of ferrujjinous conglomerate, which, when broken, looks like yellow 

 haematite with madrepore holes in it." He also notes that the same 

 formation is responsible for the prevailing reddish tint assumed by 

 the soil. In Mozambique, the province of Portuguese East Africa 

 south of Nyasaland, lateritic deposits of the kind described by Living- 

 stone are very abundant. In view of the wide interest which the 

 superficial deposits known as laterite have aroused among geologists 

 during recent years, no excuse seems necessary for placing on record 

 a few notes dealing with their modes of occui-rence and associations in 

 Mozambique.^ The country was explored during the year 1911, 

 Mr. D. A. Wray, Mr. E. J. Wayland, and myself accompanying the 

 expedition as geologists. My former colleagues have kindly placed 

 their notes on the superficial deposits of Mozambique at ray disposal, 

 and I wish here to express my indebtedness to them for the help 

 thus afforded. 



Following the nomenclature of Dr. L. L. Termor,^ the lateritic 

 deposits of Mozambique may be classified as laterite, quartzose laterite, 

 and lateritic sand or earth. Cases of the occurrence of lateritoid, 

 formed by the metasomatic replacement of the underlying rocks at 

 their outcrops, are doubtful, and, in any case, are of little importance 

 compared with the widespread occurrences of other types, the chief of 

 which is quartzose laterite. The latter forms exceedingly hard, slag-like 

 masses, brown and vainished at the surface, but paler in colour where 

 unexposed to the atmosphere, as, for example, on freshly broken sur- 

 faces. The rock is frequently concretionary and cavernous, the holes 

 being occupied by a powdery ferruginous earth, or by angular and 

 subangular fragments of quartz, which with fragments of other 



^ For a short account of the geology and geography of Mozambique see 

 respectively Holmes & Wray, Geol. Mag., 1912, p. 416, and Holmes & Wray, 

 Geog. Journ., xlii.p. 143, 1913. For a map of Mozambique, prepared from the 

 results of the expedition of which the present writer was a member, see 

 Geog. Journ., xlii, p. 112, 1913. 



2 Geol. Mag., 1911, p. 514. 



DECADE VI.— VOL. I.— NO. XII. 34 



