| Und Undetermined |
| J Jurassic marine and continental strata |
| JTr Jurassic and Triassic marine and continental strata |
| JTru Jurassic and Triassic sedimentary and volcanic rocks |
| Jv Jurassic volcanic rocks, mostly andisitic to silicic |
| Jx Jurassic complex of sedimentary, igneous, and metamorphic rocks |
| K Cretaceous marine strata |
| Ki Cretaceous plutons, mostly intermediate to silicic |
| Km Cretaceous metasedimentary and metaigneous rocks, low to intermediate metamorphic grade |
| Ku Cretaceous sedimentary and volcanic rocks |
| Kv Cretaceous volcanic rocks |
| Kva Cretaceous andesitic to silicic volcanic rocks |
| My Mylonite or cataclastic zone along major fault (Guyana Shield) |
| Mz Mesozoic sedimentary and volcanic rocks |
| MzPz Mesozoic and Paleozoic marine and continental strata |
| MzPzm Mesozoic and Paleozoic metasedimentary and metaigneous rocks |
| Mzb Mesozoic amphibolites and associated metasedimentary rocks |
| Mzg Mesozoic metavolcanic and associated metasedimentary rocks |
| Mzi Mesozoic plutons, mostly intermediate to silicic |
| Mzm Mesozoic metasedimentary and metaigneous rocks, low to intermediate metamorphic grade |
| Mzv Mesozoic volcanic and sedimentary rocks |
| Mzva Mesozoic flows and small plutons, mostly intermediate to silicic |
| Pz Paleozoic strata |
| Pzi Paleozoic plutons, mostly intermediate to silicic |
| Pzm Paleozoic and Precambrian metamorphic rocks, undivided |
| PzpCu Paleozoic and Precambrian igneous and metamorphic rocks, undivided |
| Pzv Paleozoic volcanic rocks |
| Q Quaternary alluvium |
| QT Quaternary and Tertiary marine limestone, sandstone, and shale |
| QTc Quaternary and Tertiary continental deposits |
| QTv Quaternary pumice fills and pyroclastic mantles |
| Qv Quaternary volcanic edifices, flows, and pyroclastic deposits |
| Qvi Quaternary pumice fills and pyroclastic mantles |
| T Tertiary marine strata |
| TK Tertiary and Cretaceous marine strata |
| TKc Tertiary and Cretaceous continental strata |
| TKi Tertiary and Cretaceous plutons, mostly intermediate to silicic |
| TKv Tertiary and Cretaceous volcanic rocks |
| TKx Tertiary and Cretaceous complex of deformed sedimentary rocks |
| Tc Tertiary continental strata |
| Te Eocene strata |
| Ti Tertiary plutons, mostly intermediate to silicic |
| Tmov Miocene and Oligocene volcanic rocks |
| To Oligocene strata |
| Tplv Pliocene calc-alkaline volcanic rocks |
| Tpm Pliocene and Miocene strata |
| Tv Tertiary volcanic rocks |
| Tva Pliocene and Miocene andesitic flows and associated volcanic rocks |
| W Water |
| e Eclogite |
| g Gabbro and related rocks |
| i Intrusive rocks, undivided, mostly intermediate to silicic |
| lKv Lower Cretaceous flows, breccia, and tuff, partly of marine deposition |
| lT Eocene and(or) Paleocene marine strata |
| lTv Eocene and Paleocene volcanic flows and associated pryroclastic and volcanogenic sedimentary rocks |
| pCa Precambrian amphibolite and associated metasedimentary and metaigneous rocks |
| pCd Precambrian diabase sills and dikes. Ages 1,500 - 1,750m.y. |
| pCg Precambrian granitic rocks. Ages 1,800 - 3,140m.y. |
| pCgn Precambrian quartzofeldspathic gneiss, ferruginous quartzite, and banded biotite gneiss |
| pCi Precambrian granitic rocks. Ages 1,000 - 1,550m.y. |
| pCl Precambrian granulite, migmatitie, and iron-formation |
| pCm Precambrian metasedimentary and metaigneous rocks, undivided |
| pCmv Precambrian metamorphic rocks of low grade |
| pCsv Precambrian metasedimentary and metavolcanic rocks |
| pCu Precambrian igneous and metamorphic rocks, undivided |
| pCum Precambrian ultramafic rocks |
| pCv Precambrian silicic flows, tuffs, and ignimbrites |
| u Ultramafic rocks |
| uK Upper Cretaceous marine strata |
| uT Post-Eocene marine strata |
| uTc Post-Eocene continental strata |
| v Volcanic rocks |
