Microstructure of mudrock and the choice of representative sample

The advent of high resolution microscopy has increased the scientific community understanding on the heterogeneity of mudrock. There are numerous ongoing efforts to understand micro to nanometer scale pore and pore network in shale which is related to the microstructure. Despite the wide interest in understanding the micro-nano meter scale features in shales, previous microstructural studies have been restricted to small parts of the sample which may not be representative of the whole sample. The best past practice has been to produce manual mosaic images involving combination of images with about 25% overlap. Here we present our preliminary results from a number of polished thin sections of muddy contourites from IODP expedition 317. Mosaics up to several thousand of tiles in size were automatically collected and stitched, using high resolution scanning electron microscope, with tile overlap of approximately 10%. The result shows variation in microfabric and dissimilar orientations within the same slide. Hence, understanding the microstructural characteristics of mudrock over wide mosaic tiles as shown in this study is important to reveal their heterogeneity and constraint critical evaluation of their physical properties.