The oldest rocks in Venezuela formed during the Precambrian and occupy the Guiana shield in the southern tier of the country near Guyana and Brazil, east of the El BaUl swell.
Metamorphism and intrusive activity formed gneiss with sedimentary and igneous protoliths around 1.8 billion years ago.
Geochemistry research on the Imataca Complex within metaigneous and metasedimentary rocks reaching granulite grade on the sequence of metamorphic facies suggests high temperature decompression, based on assemblages of sillimanite, kyanite, garnet, orthopyroxene, plagioclase and quartz.
Research in the Merida Andes in the 1960s revealed unmetamorphosed sedimentary rocks from the Ordovician, Silurian, Carboniferous and Permian, as well as metamorphosed slate.
[4] The Merida Arch, a remnant mountain range from the Pennsylvanian controlled sedimentation in the Tachira, Barquisimeto and Machiques as well as the Maracaibo and Barinas basins.