3 Results
Figure 1. For each sample, the left column reports the geographic coordinates, length (L), diameter (D), density (ρ), and porosity (Φ). The three center columns are pictures of hand samples and transmitted light microphotographs. The right column reports mineral compositions according to X-ray diffraction analyses (XRD).
The four samples are mudstones containing more than 60% quartz and feldspars. The remaining minerals are calcite, chlorite, and clays representing at least 20% of the total volume. Resource limitations impeded us from separating the abundances of micas and illite-smectite clay minerals. Porosities vary between 7 and 18%, where the tighter samples (MT07 and MO02) have a longer diagenetic or metamorphic history. Microphotography reveals that the grain size varies significantly among the four samples: Sample GB13 has the smallest grain size (<20 µm), while MT07 presents the largest grain size (<300 µm).