Mudrocks

Mudrocks are one of the several names for fine-grained, argillaceous sedimentary rocks, also broadly called shales and mudstones, all of which consist mostly of terrigenous clay and silt along with some carbonate and organic matter. Mudrocks occur either as thin beds or in thick sections, but some siltstones, sandstone, or carbonate beds are nearly always present and rare is the section of mudrocks that does not pass laterally into interbedded carbonates or sandstones somewhere along its limits (Figure M21). Mudrocks thus may form but a small part of a deposit or almost all of it with names such as London Clay Formation, Rhinestreet Shale, Quamby Mudstone Group, Cambridge Argillite, etc.

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