Pore size, shape and connectivity in tills and their relationship to deformation processes

Abstract

This paper describes how till bulk porosity and pore shape, size and connectivity relate to till deformation processes. Methods have been developed to examine till pores microscopically using thin section analysis, scanning electron microscopy (SEM) and X-ray computed micro tomography (μCT). Porosity is quantified using digital image analysis of thin section images from the petrographic microscope and SEM and from X-ray μCT. These methods were applied to a selection of Pleistocene tills with diverse properties. The micromorphological techniques have allowed porosity to be related to other till microstructures. Most of the microstructures examined, including the pores, have been interpreted to be indicative of either plastic or brittle subglacial deformation and the type and extent of till deformation has been interpreted to affect bulk porosity, pore type and pore connectivity.