This project aims to increase the understanding of the distribution of iron clay minerals, sulfides and carbonates that form during and right after deposition of sandy sediments. The relation between geochemical conditions, depositional environment and reworking processes is of special interest. Sediments deposited in shallow marine environments may be reworked by waves, currents and tides after initial deposition and such processes will alter the texture, composition and redox conditions within the sediment.
Understanding natural mineral formation processes in natural marine environments related to respiration processes is a prerequisite to understanding any pH or redox-driven process that leads to the redistribution of chemical components in subsurface sediments. The Tilje/Garn/Cook Formations have been chosen because they contain diagenetic iron-rich minerals representing different redox conditions (post-oxic, sulfidic and methanogenic respiration). The resulting physical and chemical alterations taking place right after deposition may have a profound influence on later physical and chemical changes taking place in such sediments during deeper burial.
The work will be based on the characterization and comparison of geophysical logs, constructed sedimentological logs of core material and thin section samples from relevant intervals on the NCS (Garn-/Tilje-/Cook Formations). Data and results based on electrical logs and sedimentological logging will be compared to investigate the distribution of sedimentary facies. The facies distribution will be related to the petrographic analysis of core material using both optical microscopy and scanning electron microscopy (SEM).
The work will contribute to a better understanding of natural mineral formation in iron mineral-prone sandy sediments. Of the possible iron minerals forming in such sediments clay minerals are of special interest. The distribution of these minerals in sandy sediments may be important for several different reasons; they may affect aquifer properties and water quality, they may enable mineral trapping during CO2 storage in subsurface reservoirs and they play a crucial role for subsequent burial cementation and reservoir quality distribution in deeply buried sandstones.
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