Earth Bytes: Norwegian Journal of Geology:open access high-quality geology journal

The Norwegian Journal of Geology is an open access high-quality geology journal,

and the latest issue would be of interest to all those working in geomorphology. Each paper is downloadable as a PDF file.

This paper " Diagenesis and weathering of quartzite at the palaeic surface on the Varanger Peninsula, northern Norway" by Jakob Fjellanger & Johan Petter Nystuen is especially interesting and examines the weathered zones in quartzitic bedrock on the Hak alancˇearru Mountain on the Varanger Peninsula, northern Norway, and the timing of their development. The weathered zones are mainly associated with fractures formed by tectonic shear. SEM, microprobe and thin section studies reveal features belonging to the diagenesis and weathering history of the rock. Flakes of phyllosilicate minerals were originally deposited together with the quartz sand and became attached as coatings to the surface of individual quartz grains as well as forming an intergranular fill. Some of the detrital clay minerals turned into kaolinite during an early stage of the burial diagenesis. Kaolinite was later partly transformed to dickite. Quartz dissolution with concomitant quartz cementation and illite formation took place during later burial diagenesis. The kaolinite occurs in intergranular voids where it was partly transformed to pyrophyllite at a peak temperature of about 300 ˚C. As the overlying rocks were eroded the previously formed tectonic joints and small faults enhanced the circulation of ground water. This facilitated chemical weathering along joints and nearby grain contacts where slight dissolution of quartz significantly weakened inter-granular bonds. The resulting increase in permeability facilita-
ted recent disintegration of the quartzite by mechanical processes. The chemical weathering is interpreted to be older than the Quaternary, possibly much older, and has implications for blockfield development and quantification of glacial erosion. It is speculated that the weathered zones may represent the lower parts of a previous deeply weathered crustal layer which may be coupled to the formation of the quartzitic inselbergs, e.g. the Hak alanc ˇearru Mountain, on the palaeic surface. The study shows the importance of combining geological and geomorphological methods to unravel complex geomorphic processes.