New Global Geological Maps of Crustal Basement Age

Most geophysical studies involve a comparison of the results with the geologic setting, particularly the age of the crust and the tectonic setting. However, continental geological maps typically display the surface geology of the Earth that may consist of younger cover rocks overlying older crystalline rocks (basement). Here we present alternative geological maps whereby the sedimentary or volcanic cover rocks have been removed in order to reveal the deeper basement rocks of the continental crust. These new basement geological maps present the continental crust in terms of the age. This age may refer to either the time of crustal formation (extraction from the mantle) or the time of crustal reworking (thermal or tectonic), that occurs during a major orogenic event. We have prepared both a global map, and a series of continental maps for North America, South America, Australia, Eurasia, and Africa. Oceanic crustal age is also indicated. The primary purpose of these basement geological maps is to provide base maps for geophysical and geochemical studies of the origin, modification, and preservation of continental crust. The age of the continental crust is subdivided into seven time units. There are four units for the Precambrian: Archean (3.8-2.5 Ga), Paleoproterozoic (2.5-1.6 Ga), Mesoproterozoic (1.6-1.0 Ga), and Neoproterozoic (1.0-0.54 Ga) and three units for the Phanerozoic: Early Paleozoic (543-400 Ma), Late Paleozoic (400-250 Ma), and Mesozoic-Cenozoic (250-0 Ma). These maps were compiled from published geological maps together with new geological and geophysical data on the age and subsurface extent of basement rocks. These basement geological maps provide a context for evaluating global and continental scale models of crustal evolution.