Geochemical evaluation of the Late Paleocene and Early Eocene shales in Siri Canyon, Danish-Norwegian Basin

Late Palaeocene to Early Eocene shales are widely distributed in Siri Canyon located in the Danish-Norwegian Basin. Geochemical study on the Late Paleocene-Early Eocene shales has revealed a common provenance of intermediate rocks, and the Rogaland anorthosite complex located in the southwestern Norway is supposed to provide the source materials. The litho-components of Late Paleocene shales were exposed to intermediate-strong weathering, and a decrease of weathering degree that probably accompanied with a shift to less oxic depositional environment was observed for the Lower Eocene shales. The change could be related to continental rift that associated with the opening of North Atlantic rifting zone at ∼56 Ma. Spatially, there is little elemental variability among the shales from different oil fields, except distinct lower Na contents in shales from the Cecilie field. The transformation of smectite to illite at greater deepth in Cecilie filed may release more Na which acts as an interlayer cation in the smectite.