These projects aim to increase the understanding of the distribution of grain-coating iron clay minerals, sulfides, and carbonates that form during and right after the deposition of sandy sediments. The relationship between geochemical conditions, sedimentary depositional environments, and reworking processes is of particular 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, producing iron-containing minerals within the sediment.
Understanding natural mineral formation processes in marine environments related to respiration is a prerequisite for comprehending any pH or redox-driven processes that lead to the redistribution of chemical components in subsurface sediments. The Tilje, Tofte, Ile, and Garn Formations have been chosen because they contain diagenetic iron-rich minerals that represent different redox conditions (post-oxic, sulfidic, and methanogenic respiration). The resulting physical and chemical alterations that occur right after deposition may have a profound influence on subsequent changes in such sediments during deeper burial.
The work will focus on the characterization and comparison of geophysical logs, constructed sedimentological logs of core material, and thin-section samples from relevant intervals within the different formations. Data and results from 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).
This thesis work will contribute to a better understanding of natural mineral formation in iron mineral-prone sandy sediments, as well as how such minerals affect sediment properties during burial. Among the possible iron minerals forming in these sediments, clay minerals are of special interest. The distribution of these minerals in sandy sediments may be important for several reasons: they may affect aquifer properties and water quality, enable mineral trapping during CO2 storage in subsurface reservoirs, and play a crucial role in subsequent burial cementation and reservoir quality distribution in deeply buried sandstones.