A 3rd order theory of folding of viscous multilayers indicates that forms of folds are controlled by the behavior of layer contacts or interbeds, the relative stiffnesses of the multilayer and confining media, and the scale of the folding. A 2nd order analysis shows that asymmetry of folds is determined largely by the behavior of layer contacts and the sense of layer-parallel shear during folding.
Alkylammonium ion exchange, x-ray powder diffraction (XRD), x-ray fluorescence spectroscopy (XRF), and high resolution transmission electron microscopy (HRTEM) have been used to study the chemistry and the physical properties of illite/smectite (I/S) clays from Paleozoic K-bentonites. The data have been used to evaluate current models of I/S interstratification and the mechanism of formation of illite during bentonite diagenesis.
Petrographic study of the Deicke and Millbrig K-benonite beds (altered volcanic ash) of Rocklandian age has revealed that they can be distinguished by their non-clay mineralogy. The Deicke phenocryst assemblage is primarily labradorite, Fe-Ti oxides, apatite, and zircon, while the Millbrig assemblage is primarily andesine, quartz, biotite, apatite, and zircon. The Deicke is altered dacitic ash, while the Millbrig is altered rhyodacitic ash.