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).