Comparison of the buried bauxite deposits of the Onverdacht-Lelydorp area in Suriname (northern edge of the Guiana Shield) with those of the Trombetas area in Amazonas-Para, Brazil (southern edge of the Guiana Shield) reveals essential differences in: (1) the age and duration of the bauxitization process (Eocene-Oligocene at about 20 m.y. and Pleistocene at about 1 m.y.); (2) the mineralogy of the iron component (exclusively hematite and a mixture of hematite and aluminum-bearing goethite); (3) textures (mainly concretionary and cellular textures compared with granular and massive textures); and (4) the character of the covering layer (Miocene and younger unconsolidated sediments against Pliocene residual soil).The geographic position, climatic history, and parent rock in both areas are as similar as ever can be expected in geology; thus, the differences between the bauxite deposits in both areas can probably be attributed to the differences in age and duration of the bauxitization and to the presence or absence of a postbauxite sedimentary cover.

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