Origin of the “Beef” in the Lias Shales of the Dorset Coast.

Summary

It is believed that the “ beef ” in the shales-with-“ beef ” resulted from the leaching of the CaCO₃ of a fine porous marl by a groundwater solution, and its subsequent redeposition. The initial redeposition was about the grains of calcite along bedding planes or similar divisional openings, and, as more material was added by the solutions moving to these planes, each original grain developed into a fibre in the layer of “ beef ”. Growth was from both sides, but took place faster on the upper side because the dominant movement of the water was downward. Growth stopped due to the exhaustion of the supply of CaCO₃ in the marl or CO₂ in the solution. The thin paper-shales between the layers of “ beef ” may represent the concentration of the original clay of the marl. This explanation of the origin of the “ beef ” would probably apply to other fibrous deposits of calcite, also.