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We quantitatively analyze the area‐age distribution of bedrock based on data from the most recent geologic map of the conterminous United States of America [ King and Beikman, 1974a , 1974b ], made available in digital form by the United States Geologic Survey. The area‐age distribution agrees surprisingly well with older data [ Higgs, 1949 ] but provides much higher temporal resolution. The mean stratigraphic age of all sedimentary bedrock is ∼134 Myr; that of Tertiary‐Cambrian sediments is ∼104 Myr. The analysis also reveals area coverage of some minor lithologies, such as ultramafic rocks that cover ∼0.15% of the conterminous United States. Area coverage of 162 lithostratigraphic units is made available as an Excel data sheet.
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Peucker‐Ehrenbrink et al. (2002) studied this question.
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