Organic Carbon and Trace Metal Distribution in the Gökçesu Shale: Eocene Basin, Bolu-Turkey

Abstract

Samples collected from the bituminous shales in the Eocene Tokmaklar formation are the material of this study. Distribution of organic material and trace metals in the shale samples and their concentration levels and correlations were evaluated. Organic carbon content of the bituminous shales is between 0.59 and 15.89% (averaging as 4.86%). The type of organic material is 100% amorphous material (kerogen type is Type I and Type II) and it has a potential to produce oil. Trace metal enrichment levels were determined on the basis of average shale concentration in the earth crust. These levels are divided into two groups. Mo (1.98–2.64), Cu (1.27), As (1.59–8.83), and Sr (2.58–2.75) in bituminous rocks show enrichment character while Pb, Zn, Ba, and Co metals do not display any enrichment. Moreover, comparison with the average values of these metals in seawater and living organisms yield enrichment coefficients of 86.17–386.000 (with respect to seawater) and 4.59–1,723.5 (with respect to living organisms).

Keywords:

• bituminous shale
• Eocene basin
• living organisms
• organic carbon
• trace metal

Acknowledgments

We thank the Research Foundation of Ankara University for financial support of this work through the Project 2001-07-05-062. The authors wish to thank two anonymous referees for their critical reviews. The authors also acknowledge geological engineer Ugur Oren for helping at the field study.