Guyana belongs to the Guiana Shield, a massif extending north of the Amazon, between the Andes Mountains and the Atlantic, made up of Precambrian rocks dated to between 2.7 and 3.5 billion years ago. The shield consists of several geological units: the southern peneplain, the Inini synclinorium, the central granite massifs and the northern synclinorium. The southern peneplain consists of a set of granito-gneiss consisting of metagabbros, metagranodiorites and metagranites dating from 2075 ± 7 Ma from a magma of metamorphosed mantle origin. To the north, the southern peneplain straddles the Inini synclinorium, mainly composed of the Paramaca series, which corresponds to a series of micaschists, aluminous paragneisses and black quartzites whose total thickness is about 1 km. The central granite massifs consist of granite plutons, granodiorites and quartz diorites dating from 2.05 to 2.15 billion years ago. The north of French Guiana corresponds to a synclinorium composed of the Paramaca series on which sandstone and fluviatile conglomerates lie unconformably. Shield rocks in Guyana are all dated between 1.6 and 2.5 billion years ago.