Investigation of Organic Carbon and Trace Metal Enrichments of Rocks at the Paleocene-Eocene Boundary, NW Turkey

摘要

In this study, organic geochemical and biogeochemical investigations were conducted on various deposit types at the Paleocene-Eocene boundary in the Bolu and Ankara (Ozankoy) regions in northwest Turkey. Investigations yield that clayey and carbonaceous rocks in the Bolu and Ankara regions have high organic carbon (Corg) and Ni, As, Se, Au, W, and Mo contents. Variation range, range difference, and averages of these two parameters in the rocks were computed. In addition, enrichment factors of the elements in the fields were determined with respect to their abundance in the earth crust and shales. The average Corg content in the Bolu and Ankara regions is about 7.51 wt percent. However, in various bitumen layers this value ranges from 10-40 wt percent. The main source of OM in deposits is sapropelic or algal amorphous Type I kerogen and also Type II kerogen consisting of plant materials such as spore pollen, and leaf cuticle. Enrichment factors of Ni, As, Se, Au, W, and Mo with respect to their abundance in the earth crust are 2.93, 35.73, 144.5, 15.0, 15.25, and 3.2, respectively. Corg and element accumulation levels indicate a periodical property and the presence of a positive correlation among them. Enriched element contents are mostly attributed to an OM-dependent biogenic accumulation level. In addition, diagenetic element exchange and the element exchange particularly between seawater and bituminous material are very effective. Results of this study yielded that bitumoid-rich Bolu and Ankara regions can also be evaluated for their energy and metal sources.