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USGS2003

Chemical and isotopic properties of kukersites from Iowa and Estonia

Kukersite samples from Estonia and Iowa were analyzed for elemental composition, functional group distribution, and carbon and hydrogen stable isotope ratios. The elemental and hydrogen isotope values, together with other analytical data, suggest a higher thermal maturity for the Iowa kukersite. The wide carbon isotopic range of 9.3??? among kukersites, with unusually negative ??13C values reaching -33.2???, indicates isotopically variable carbon sources for production of biomass, and thus major paleoceanographic differences between the environments supporting biosynthesis. ?? 2003 Elsevier Ltd. All rights reserved.

Organic Geochemistry↗

USGS1996

Assessing the coal resources of the United States

In 1994, coal production in the United States reached the highest level in history (slightly more than 909 million metric tons or one billion short tons), continuing the upward trend of coal production and utilization that began 34 years ago. Previous assessments of the coal resources of the United States, which were completed as early as 1909, clearly indicated that the total coal resources of the Nation are large and that utilization at the current rate will not soon deplete them.

Fact Sheet↗