Concave upward structures in a fossiliferous laminated goethite-rich sedimentary rock (matrix is dominantly goethite with approx. 15% submicron silicate detritus e.g., clays and very sparse oxides).
We have considered stylolites, roots, ripples, burrows, or some sort of compaction feature.
The structures cross-cut bedding but don't demonstrably offset the bedding. They also appear to be slightly enriched in U and slightly depleted in Th relative to the matrix so perhaps some dissolution-reprecipitation has occurred.
Any ideas welcomed.
This is an image of a surface exposed at outcrop of a well-bedded siliciclastic sediment. Given a 2-D structure not penetrating the bedding of the host sediment I would call it a partition structure on a fissure or surface reflecting a latent stress-strain system inherent to the rock that becomes visible through mechanical natural or artificial processes and is common to many fine-grained rather homogeneous sediments, such as fine-grained calcareous sediments made up of organic debris. The slight enrichment of U and the depletion in Th is in accordance with the common behavior of these elements in supergene environments. In my opinion it is some kind of strain relief which exposes internal stress-strain relations otherwise left undetected. Among all examples listed in the preview these structure come most closely to stylolites.
HGD
Thanks for your insights, Herald. Much appreciated. This gives me a few more leads to follow. All the best.
- Badges
- Science topic