A DESCRIPTIVE ANALYSIS OF TEXTURAL FEATURES WITHIN CRETACEOUS CHAMOSITE OOIDS OF THE DALKJEGLA MEMBER, CAROLINEFJELLET FORMATION, SPITSBERGEN NORWAY

Chamosite ooids found in sandstone beds from the Cretaceous age Dalkjegla Member, Carolinefjellet Formation, Spitsbergen Norway, display several interesting petrographic features. These petrographic features include truncated and discontinuous laminae, brittle deformation of outer laminae, cross-cutting borings, and laminae with tangentially oriented crystals (T-laminae) or laminae with radially oriented crystals (R-laminae). T-laminae solely comprise most of the ooids in these samples but some samples display T-laminae in combination with R-laminae. Previous work provides evidence that the iron ooid beds within the Dalkjegla Member are storm deposits indicative of a high energy environment of deposition with two of the six localities containing petrified wood fragments.

In previous work on ooids, two end member types have been identified. Ooids are either comprised of all T-laminae, all R-laminae, or are combined with the R-laminae on the inside and T-laminae on the outside. Samples of the chamosite ooids from the Dalkjegla Member display all of the previously described types plus a unique variety in which R-laminae surround T-laminae.

Previous work has correlated the precipitation of R-laminae to marine solutions rich in humic acids and carboxyl groups allowing for organic membrane formation. It is possible that in this study, the samples in question indicate multiple growth events that can be correlated to the chemical and physical environment during their formation. Further inquiries will be concerned with the nature of these organic processes and the role of microbes in the formation of laminae.