Quantitative bedrock geology of the continents and large-scale drainage regions
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 We quantitatively analyze the area-age distribution of sedimentary, extrusive volcanic, and endogenous ( plutonic and/or metamorphic) bedrock on the basis of data from the most recent digital Geological Map of the World at a scale of 1: 25,000,000. The spatial resolution of the digital bedrock data averages 13,905 km 2 per polygon. Comparison of certain regions of the world, previously analyzed at higher spatial resolution, with the low-resolution world data reveals general consistency in the areal exposure of major rock types as well as a minor systematic bias toward older average bedrock ages in the global data set. Application of the global bedrock data to 19 large-scale drainage regions and three large, internally drained regions reveals considerable regional variability of Earth’s bedrock geology that is consistent with the dominant geotectonic setting of the respective drainage region.