Abstract Shale rocks are highly structurally and chemically heterogeneous, such that the pore structure–transport relationship is complex. Shales typically have porosity over many length-scales from the molecular up to macroscopic fractures. This work utilizes gas overcondensation to probe pore sizes from micropores to very large macropores all in the same experiment without the potential for damage due to high pressures when conducting mercury porosimetry. Indeed, the Bowland Shale samples studied here are generally inaccessible to mercury intrusion. The gas overcondensation method can also be augmented using scanning loops to assess the spatial juxtaposition of very different pore sizes, and this has been used to determine that some large macropores are shielded by pore necks less than 4 nm in size in the Bowland Shale. In addition, the adsorption calorimetry method has been used to assess the accessibility of the void space. It has been found that mass transport is limited by particular ‘hour-glass’-like pore necks that fill at quite low saturation, and thus present a barrier to molecular migration. The shielding of macroporosity by narrow necks was particularly significant for the Above Marine Band sample, with lower shielding observed in the Marine Band and Below Marine Band materials.

Abstract Time contained within coal seams is most commonly estimated using a volumetric approach that fails to take into account processes of carbon accumulation and loss during peat formation and coalification. A more appropriate approach for estimating the time contained within a coal seam is to use Holocene long-term carbon accumulation rates, accounting for carbon loss during coalification. Using this approach the thickness of coal corresponding to 10 kyr of carbon accumulation is calculated for coals of all ranks and latitudinal settings. To test the validity of this approach, latitudinal patterns of Holocene dust deposition are used in conjunction with estimated rates of carbon accumulation to calculate the concentration of titanium in coal. The result is a statistically significant correlation that is optimized when latitudinal variation in carbon accumulation rate is considered. Overall, the use of carbon produces far greater accountability of time within coal-bearing stratigraphic sequences and is not influenced by the presence of hiatal surfaces within the coal. Estimated coal seam duration increases considerably, often removing the need to infer substantial intra-seam hiatuses. On the basis of the results, a re-evaluation of coal and coal-bearing stratigraphic sequences is recommended.