Photomicrograph of glendonite concretion from storm bed in Carolinefjellet Fm., Festningen.

This is a mosaic of thin section photos of a glendonite concretion from a storm bed at the top of the Dalkjegla Mbr. within the Carolinefjellet Fm. . Clicking on it will download a 10MB version. The concretion is a bit more than 2 cms across, and the photos were taken with crossed nicols. A core of coarser calcite is surrounded by 'petals' of bladed carbonate with a complex internal texture. Given that glendonites are usually calcite pseudomorphs of a unstable hydrous carbonate mineral the texture may reflect the recrystallization process. Note between the petals the fine-grained sideritic sediment that is preserved. We interpret this to represent the sediment the glendonite grew in before excavation and deposition as part of the storm bed. It looks like the lower left large petal has been truncated by some process. Most of the black mineral is pyrite and there is a pyritization front on the left side (sedimentary bottom). The large clast in the upper left is a carbonate hardground with oolites in it, while to the lower left is a chert clast with a pyrite replament rind. For fun below is the same image but with an edge detection routine run on it.